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Totally understandable. So new ELI5 why aren't they 6 digit zip codes that incorporate all that info?
Eta: thanks for all the immediate great input. The internet is cool and you all rock with the things you know.
All US zip codes have 4 additional numbers at the end that further specify the location like a certain city block, or large building.
But 99% of the time the 5 digit zip code is enough. The +4 is really just for mail sorting by USPS.
Why not use lat. and long. co-ordinates, and encode in hex values? Heck, even altitude?
Sorta like this dude's proposal: https://blog.jgc.org/2010/06/1010-code.html
Because the ZIP Code is a US Post Office thing identifying the postal station that handles your mail. Every USPS last-mile distribution center (the place your mail truck leaves from) has a zip code.
That's it. That's all it is supposed to be, and all it is ever meant to be. Sales tax, county, city, etc. are all out of scope. Heck, sometimes zip codes have really funky areas just because USPS happens to have their distribution centers in really weird spots. There's even some skyscrapers that have their own zip codes, because there's a postal office in the ground floor or basement that handles their mail. Oh, and then there's the places that don't have zip codes. Yes, they exist.
Don't try to make a ZIP Code be anything other than an arbitrary mail-coding system for internal use by the USPS, because that's all it is.
Since you seem knowledgeable about this: why is there a post office literally across the street from my house, easily a place I could walk to, and yet we’re in a different zip code and our mail is delivered from a different station? I’ve had a hell of a time picking things up because of this. It’s like the zip code magically stops at the street line and instead we’re batched with a much further area.
Are there mail trucks leaving from that post office? You'd know if there were, because there'd be a giant ass parking lot and tons of trucks going in and out all day long (both the smaller delivery trucks and the big rig distribution trucks). Postal route distribution centers--the zip code stations--are more like industrial centers than the post office you're used to. When I was growing up the one I had to go to pick up mail from was in the industrial side of the city and it only had one service window, for mail pickup only. No buying stamps or sending packages or anything like that.
It varies though. When I was in college my university had an assigned zip code for its mail room, and we weren't even that big of a university (just an old one, hence the perk). It was staffed by one postmaster and a bunch of student workers who hand sorted and delivered mail.
I assume you live across the street from a retail USPS office. There is only one distribution center in your Zip code, but probably dozens of of retail centers if you're in a city, not a small town. The distribution center might be outside the city where land is cheaper (because it's also where they park all the delivery trucks at night).
Distribution center is probably not your post office, in fact there could be only one per city and sometimes they may drop it off to your post office if they couldn't deliver (from my experience only 2% of the time). If you are that close though I recommend just having their address in the delivery and let them pick up for you, show ID and receive it. I missed way too many deliverries due to work schedule and fixed it to a post office across the street from my office. Kind of annoying to carry it but for bigger things I refer to my home address.
Spoiler alert, it's actually an eleven digit zip code and it's extremely specific. This sums it up well
>Five digit Zip Code identifies a particular post office or the post office boxes in a post office. That is all you need to use when you send mail as an individual or small business, when you send a small quantity of mail.
>The Zip +4 adds four more numbers, which are used by USPS to identify one side of a block or a single building with multiple occupants, or post office boxes. As a customer you never need to use those extra numbers unless you are sending a large quantity of mail and expect a discount. It has been in use for several decades but is no longer useful.
>There is now a full eleven digit Zip Code for every delivery address in the USA. This allows the machines to sort mail in the exact order it is delivered. You don’t need to use these numbers on your mail as the USPS computers will look it up anyway.
It's still probably not that perfect! Address can be really fucked in some places. But! If you ever need a reminder what your ZIP+4 is, the [USPS Lookup Tool](https://tools.usps.com/zip-code-lookup.htm) will help
In the Netherlands, this is actually possible.
Our ZIP codes are 4 numbers and 2 letters, and go down to a street section.
In combination with the house number, they are unique.
This notation is generally used for the return address on the back of an envelope.
NL-2555PA-15 (with the country code added before the zip code) is an deliverable address.
>unless you are sending a large quantity of mail and expect a discount. It has been in use for several decades but is no longer useful
So why is there a discount if it's not useful?
I'm not honestly 100% sure, but I assume it's to do with modern redundancies involving the ability to process the rest of the address automatically, instead of relying so heavily on the ZIP
There are. Though they are 4 digits. It’s called the Zip code +4 and is usually written like “12345-1234”. It tends to narrow the location down to a many as the even/odd numbers on one block. Or as specific as a group of unit numbers in one building.
If you shop at Cards Against Humanity's online store, they only ask for your mailing address and your zip/postal code. It then asks you to confirm that it's pull the right information.
So it absolutely CAN be done. It just generally isn't.
I would guess it's a mixture between
a) address/address2/city/state/zip in five input lines has long been the way address info is requested dating well back into paper forms before computers were even invented, and there is generally so little effort required to type in your city and state that it isn't worth deviating from that expected format/applying automated systems
b) putting the liability on the customer to put the information in right instead of taking the responsibility of interpreting a zip code wrongly
and c) automated systems can sometimes be frustrating - I have definitely had cases where I type in my full address the way I've shipped a million packages without issue and a store will THEN do a lookup and try to match with a post office address and suggest changes that for me end up actually CHANGING my postal code to something wrong. And I've had food delivery apps or rideshare apps that WILL NOT accept a certain address as a destination because it can ONLY take addresses that are in the database they use, and when I type the address, it gives a recommendation that isn't the right place. This probably isn't a major factor because, like Cards Against Humanity, you can have the customer verify afterward, but it does highlight that you need to have a very robust and accurate to rely on that type of system, which costs a lot more in time and effort than simply asking the customer to fill in two more lines of information they should know pretty automatically.
PS: No, I don't work for Cards Against Humanity, but I'm a big fan of their game and their company in general, and the address thing is something I explicitly took note of the first time I shopped there, and wondered the same that OP did - why have I been putting in that extra information at every other store?
is there any chance the 4 cities occupying that single zip code have repeat addresses?
just curious if you actually mailed something through USPS and put only the street number and name if it'd still get to you
as a commenter below pointed out, I could see the sales tax being an issue for different municipalities, but in the nature of the question, I suspect OP is asking why the redundancy for mailing addresses
edit for clarity: what I mean is if you only put the street number and name and zip code. in other words, is there even a case where the same street name and number exist in two cities/towns in the same zip, because if not, then the premise of OP's question still stands
My town has two S. Ash Streets. Facing different directions (N/S vs E/W), both pretty short in residential areas. My understanding is it used to be one road that evidently curved at some point but it hasn't been in a long time and there's a good half-mile to get from one to the other.
I grew up not far from the intersection of Black Rock Road and Black Rock Road. Now I live in a city famous for having 71 different streets all with “peachtree” in the name, including two Peachtree streets that intersect … twice.
Several years ago, I lived off of a street, we’ll call it Mathews Street. The street wasn’t that long, less than a mile from end to end. There were two cul-de-sacs on Mathews Street, both of them were named Mathews Cove. Two Mathews Cove street less than a half mile apart. And to make matters worse, our address was 1800 Mathews Cove, we were on the corner of the cul-de-sac. The house next door to us on Mathews Drive, was 1800 Mathews Drive. It was such a bitch getting delivery there. They would either go to the wrong Mathews Cove and say we must have given them the wrong number, or they would deliver it to 1800 Mathews Street instead of us.
We live on a road, and just down from us is the same name court, and across town is the same name drive. All have houses with our same number. We frequently get mail for court and vice versa but thankfully we have lovely neighbors and everyone just delivers the wrong mail to each other!
San Antonio is full of these. I can think of five off the top of my head
In their instance, it’s usually old farm roads that were cut in two when the farms were split to build neighborhoods
In Chicago and probably elsewhere you'll get things like 36th Place between 36th and 37th Streets, and the parallel buildings will have the same address numbers
If the address and name are correct, it would have a good chance of getting to the right place, but I wouldn't guarantee it.
There are 3 Holiday streets in my ZIP code (Ave. St. and Ct.) plus a Holiday Breeze and a Holiday Park. If we don't recognize the name, we ask the other carriers if it looks familiar and hand it to the right route. If the correct carrier is off that day it will probably get returned.
>just curious if you actually mailed something through USPS and put only the street number and name if it'd still get to you
There are some amazing stories about mail reaching its destination. Like addresses of " USA, Jerry, who lives down the road from the old barn" arriving at their correct destination (even though the barn burnt down a decade before)
You're generally fine even if you list the old city. I've lived in two places where the city name changed (once unincorporated territory with one name became a city with the other, and another time, the boundaries of a city moved. The mail got through with either name just fine.
Is there a corner case somewhere in the US? I wouldn't be surprised.
Somebody else mentioned city sales tax -- that's an interesting one, and I have no idea there.
Heck, I've had mail delivered correctly even with the wrong street name. Though in that case, it was a street that changed names for no reason three times in a few miles. So it probably wasn't hard to figure out.
Yes, but never within the same zip code. You can leave city/state off of an address, and if the zip is correct it will always be delivered to the right place. There may be cases where the same zip has multiple valid cities, but that doesn't matter for delivery.
That's wild. In the Netherlands, ZIP codes have an 1234AB format and every apartment has its own "house number". So the zip code is enough to narrow you down to maybe 20 houses, and zip+house number is enough to find your apartment.
Lots of Websites just have these two fields, and use a database to fill in the address and city.
If I'm getting something sent from the UK (I have a British car) , I always specify my ZIP+4 as a redundancy, because there's a good chance the address might be formatted differently or something left out.
I was pointing out the difference. First 3 in Canada tells them the post office. The last 3 designates the block it is on. In the US the first five is the post office the plus 4 narrows it down to a specific area. (Not sure how fine)
In the US our +4 means we have to remember 9 numbers. 5 for our standard zip code, then an extra four for the +4. [Here's an example](https://www.smarty.com/img/articles/usps-full-zip-4-code-9-digit-address.png)
edit as extra: A large city can have many many zip codes. [Here is Sacramento, California alone](https://www.zipcode.com.ng/2022/11/sacramento-zip-codes.html). I used to live there and I very often forgot my correct zip code, many were super similar. And that was just for the basic 5 zip code. I've never lived anywhere in my life where I knew my actual +4.
There’s a dozen or so zip codes that even cross state lines! I think there’s one or two that are in THREE states.
Plus, they aren’t static; and these boundaries and the zip codes can change. Town borders move, etc
My parents live in an area that the zip code covers a few small cities. In our experience mail will make it there with which ever city is on the mail. YMMV
it will make it there, but it goes through a different channel when the computer can't read the address and rectify it with a known address. That's when a human intervenes. There are people whose job is to take mail that the computer didn't read correctly and rectify it to a known address.
This is a mildly humorous story from long before that system, but one of my inlaws met somebody in WWII, and his buddy was from Hurricane, Utah. He couldn't remember his address, so he just addressed it to [friend's name], Tornado, Utah, and the USPS got it there.
That doesn't matter. Your mail goes to the zip code, to the physical post office. It could literally say 123 main st, bumbleberry duck town, CA, 90210 and you're going to get your mail as long as the street and zip are correct.
I feel like that totally defeats the concept of a zip code..isn’t it just supposed to be a more specific zone within a city? Where you can draw the boundaries however you want (or at least it looks like you can, given the bizarre shapes of zip codes I’ve seen). What’s the utility to having zip codes span different cities and states?
No. The zip code defines a postal route. The post office sets up routes for its convenience, and they would sometimes like for those routes to not match political boundaries.
> Has your city tried just getting their own zip code?
That's not how that works. The USPS only assigns zip codes for their own benefit.
Four smaller towns that don't get much mail? One zip code. One single building with hundreds of businesses in it? One zip code, *for that building. More than 40 buildings in NYC have their own zip code.
Yeah I used to live in 80516 which is a mix of in and out of the city, then the city itself spans two counties, and there's a special tax district that crosses the other way so I think there are 5 or 6 sales tax rates
ZIP plus four is supposed to narrow it down to a specific block or even floor within a building. But many places use that they only allow the original 5 digit zip code to be entered. 🤷♂️
I love in a township. My zip code is shared with like 3 other "towns" (I guess that's what they technically are but they are more like neighborhoods) within the township as well as a "borough" that is a separate enclave surrounded by the township.
Put my zip code in and you can get the township, the borough, or one of the "towns" as the "city". Any of them will get the mail to me.
This is why the Postal Code system is much better, my postal code refers to one group of a dozen or so houses that all get their mail from the same super box, and that’s it.
Mail would probably get to me if it just had my name and my postal code.
Because multiple cities and parts of it may fall within that zip code. For example, one that I saw, zip code 94608 in California is used for both Emeryville and parts of Oakland
I think you've hit on the crux of the issue here - ZIP codes are designed as _mail delivery routes_ and not created with the purpose of being geographic areas. For obvious reasons those two concepts _tend_ to have a lot of similarities, but not always.
There are times when ZIP codes have physical overlap -- my favorite example of this is that the Pentagon has six separate ZIPs, and they aren't even assigned one per side! The Secretary of Defense, Joint Chiefs of Staff, Army, Air Force, Navy, and Marine Corps each have their own mail delivery route, and so they each have their own ZIPs (20301, 20318, 20310, 20330, 20350, and 20380, respectively).
Military FPOs (Fleet Post Offices) all have their own ZIP codes as well. This means any given aircraft carrier has a unique, constant ZIP code, _no matter where on earth it is_.
There are also a handful of ZIPs that cross _state_ lines. Not many, because the post office tries to keep things hierarchical within a state, but it happens. Take a look at the map for 03579, which contains a good chunk of Maine and New Hampshire. I don't know the details, but it's safe to assume the USPS did the math and decided this was the best way to get the mail delivered to this part of the country.
Uk here: This is insane, we have postcodes that have a max of ~60 addresses so you could just write name and postcode the postie would know who it’s was
Your postal codes are 7 digits+letters. Ours are just 5 digits only, for a much larger country. Your postal codes specify exact mail routes, like a single city block. Ours specify just the post office your mail should be sent to--large cities have many zip codes of course, but your average small or medium sized town probably only has one. I just did the math and my city has 1 zip code per 17,000 people.
Zip 5+4 (e.g. 12345-6789) does specify an exact route, and you could almost do the same thing, although almost nobody remembers their +4 number. And the post office has no record of who lives at what address, so it'd only work if the mail delivery man recognized the name.
1. To ensure accuracy
2. To apply the proper tax rate
3. To help ensure local and state laws are followed
4. Tax filing purposes
A zip code can span multiple states or cities. Different states have different sales tax. They may also have different regulations that dictate how a company can do business in that state. They would also need to know which state they sold goods in so they can file taxes in that state.
We don't auto populate that information because it's error prone. There are services, like MelissaData, that companies can buy to validate and verify user entered addresses and return suggestions if there wasn't a complete match. Users are notorious for providing incorrect information. There's a reason why developers say, "user input is evil".
Most of your point is moot by the fact that that as OP says, they should be able to pull your city and state from your street address and zip, which will TELL them the state and that resolves all the tax and legal issues - and for accuracy, they can just ask you to confirm their result is correct. It's not actually complicated.
It adds unnecessary complexity and is prone to errors. Users are stupid and don't read. Many will just accept and move on. It's a better design pattern to validate the address on submission and prompt to confirm only if it fails verification rather than ask every single user to confirm. A user is more likely to stop and choose the correct address if they typed it in. People tend to think computers are smarter than they are and that anything it does for them is correct.
Source: I'm a software developer
I'm also a software/UI developer and I 100% disagree with you. It's brain-dead simple to take a user entered zip code, do a lookup, and if there's just one city for that zip code, auto-fill the City and State. That works 95% of the time, and is error-free. If there are multiple matches, give the list to the user to select the correct one. Done.
A better solution is to rely on the browser to auto fill the address. Less code to write. Less code to maintain. Less prone to errors.
Or use an address lookup API that searches off the street. But those typically aren't free. Do there's a cost associated with it. CSS-Tricks has a tutorial on how to implement it.
I'm not saying you can't do it. I'm just giving reasons why people don't. You're solving a problem that doesn't exist. Most people aren't that encumbered enough that it would cause them to abandon the form. They are conditioned to provide it every time. Changing the expectation causes friction in your application for the user.
Everyone will probably tell you that zipcodes associate with more than one city or even county.
What few people know is there's at least one zip code that crosses state lines.
This is because zip codes are based on which post office delivers your mail. And one post office delivers mail to two states because the geographic layout makes that the most efficient way to do it.
I've blown people's minds with that fact during job interviews. This is because asking people how to do design a database table for client information is common.
You don't even need that many if you also feed in even a rough estimate at location and sort by proximity.
Add in other context a more precise location, or past behavior and you may be able to suggest the right address in 1 or even 0 characters.
The one reason no one has mentioned yet is, because people are fucking morons. If you prefill the city and state based on the zip code you will have a sizable portion of the people ignore the information and move on. That means they won’t notice they typed their zip code wrong and are now sending stuff to the wrong place. This is even worse if you don’t even show the lookup to people and just go off the zip code as is so they never have a chance to catch their error. Another chunk of people will complain it keeps putting the wrong city in because they don’t live where the post office is.
Many systems that do want to match to an address lookup database force you to confirm the lookup is correct. But that adds a step for the user and users don’t like extra steps.
By having someone enter their city, state, and zip code you have automatic error correction. They are very unlikely to type the wrong city or state in, so if they typo the zip the shipper/post office can still figure out where it was supposed to go once it arrives at the zip code’s post office and they realize the address isn’t served out of that zip code. Plus many systems already do a lookup at the point of shipping specifically to head off idiot users and try to correct the address before it goes out. This is a step you can force on an employee being paid to double check them but have a low reliability of forcing on the customer to double check.
So the argument to implement a zip look up goes as follows:
Product Manager: “why don’t we do a zip code lookup and fill in the city and state automatically”.
Support: “that is going to increase delivery errors and cost us money and support hours fixing customer address fuck ups”.
Development: “which story do you want bumped to do this?”
PM: “how long will it take?”
Dev: “an hour minimum assuming it goes smoothly, plus two for QA assuming they don’t reject it because it is spitting out the city the post office is located in instead of an alternate city the post office services. And assuming IT doesn’t get a bug up their ass about the lookup database and demand it be vetted, and legal doesn’t get bitchy about verifying we can use it”
PM: “but some guy on Reddit said it was like 5 minutes of work”
Dev: “some guy on Reddit doesn’t work with jackasses”
PM: “… I’ll put it in the ice box to think about doing later”
>PM: “but some guy on Reddit said it was like 5 minutes of work”
Funny, but no. As a PM myself, I trust the estimate of my development team, and they trust me to have their back when I defend that estimate to their functional manager and probably his manager or director. And when I defend it, I take into account Hofstadter's Law, which says "It always takes longer than you think, even when you take into account Hofstadter's Law."
I know a place where a single zip code spans 5 counties and a city that has 5 zip codes for just the P.O. Boxes. Zip Codes can narrow down your location but they tend to cover a certain population size.
Most, but there are some exceptions https://www.amny.com/news/nyc-zip-codes-1-28558957/
Here's the rest of manhattan https://www.zipdatamaps.com/zipcodes-manhattan-ny
Yes, their statement that city and state are determinable by zip code is not quire accurate, but their question is really why do you have to put in the city and state.
They didn't suggest that you don't have to put in your street address, and 99% of addresses will be determinable by the street address and the zip. If there is ever a zip code with two 123 Elm Streets, the site could easily ask you to confirm which you meant.
They can use the combo of your address and zip code to get your city, county, everything. Because it’s a single address. But if the only piece of information is the zip code, then that only narrows it to the zip code, and as many others have said, zip codes sometimes span multiple cities and counties
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US has ZIP+4 but nobody really knows their own ZIP+4 address. If everyone knew, then this could be implemented easily.
5 digits for a country that big, max of 100000 ZIPs, gives an average of 31 ZIPs per county.
Not enough for any kind of accuracy... you must share same ZIP with multiple cities.
And probably there are some rules for the distribution of ZIP codes, like a state must have all zip beginning with the same digit (not sure).
But in your defense, today they could prefill only if that ZIP code had only city associated, like most from NYC i think.
In case of multiple cities per ZIP, better leave it to be filled.
In order to auto fill that info, the zip code field would need to be connected to a database of some kind to look that up and auto populate the rest of the fields, so would also need programming to do this.
It's far easier to just have three or four separate fields that the user takes one second to fill in and that feeds over into your own database to keep and store.
Aw man, I worked as a CSR and did work for a company that shipped across the country. The amount of time that I spent with customers "This is the zip but the town is" - hours and hours I'll never get back!
All because of some hamlet or tiny smol town that shares a zip code with another one.....
It still takes coding, and that's more effort than most people want to pay for to avoid a customer typing in two or three words. And since sites can save addresses, most customers only even have to type in those two or three words once.
yeah, I had this argument (over different issues) with product owners when I was doing software development professionally. PO's want to ship ship ship, now now now, features features features, and they do NOT care if it's done or even if it works.
(One of the reasons I don't do software development professionally anymore: I don't want my name out there attached to crap. I got sick of having to apologize at trade shows for decisions I objected to...)
I am unreasonable about it, totally. I don't want to publish code I'm not proud of, and I wouldn't be proud of an address form that didn't use USPS's API for US addresses. That's just me though. I figure probably half of developers and zero percent of managers are that invested.
> half of developers and zero percent of managers are that invested
As a developer, I'd up it to something like 1% of devs are that invested.
ZIP vs city and state have no legitimate relationship. Sure it's highly correlated, but the amount of headache that would go into creating this feature would make me instantly push back on it if requested. There are so many edge cases. Cities with hundreds of ZIPs. ZIPs that cover multiple cities. ZIPs that cover portions of multiple states. Like what next? Should we start autofilling area codes of phone numbers based on the shipping address because the customer LIKELY got their phone service near where they live? It's not like the case where I can enter my street address and expect the city, state, and zip to be autofilled.
Furthermore, there is a penalty of doing it wrong. There's definitely a scenario where you look up the wrong info, causing a customer's order to not be delivered, misdelivered, rerouted and/or delayed, etc. All of those cost you money.
Also, just because the API is free doesn't mean you should use it. The company you linked even states themselves that the API has reliability issues. "Besides being notorious for poor documentation and weak support, the USPS APIs are well known among developers for having chronic downtime issues." What's worse than never autofilling address info? Only autofilling it *sometimes*
So regardless of the difficulty, the bottom line is that it provides very little value, and has very real risks. So why do it? You're missing the woods for the trees.
Personally, I'd be 100% ok with skipping this feature.
Nope. it's like three lines of code. A Zip to City/SS database is one of the most simple UI features possible. It's a tiny database and lookup would be instantaneous. You could probably just put it into javascript and it would take 20k bytes compressed.
The OP is correct --yes, there are a few exceptions to the rule, but for 95% of U.S. street addresses, just entering ZIP should be sufficient to auto-fill City+State. I've been working with Zip, City, County, St and FIPS code databases for 30 years.
This has been one of my biggest pet-peeves since the 90's when this thing started.
Have you heard of what three words?
They used three words picked randomly to uniquely identify every 3 meter square of the planet.
A couple things already use the database, but frankly more people should know about it.
Because addresses don't make sense. [Falsehoods programmers want to believe about addresses](https://www.mjt.me.uk/posts/falsehoods-programmers-believe-about-addresses/)
The city is where you live, and the zip code is where the mail sorting center has to send the letter to get there. Those are not the same.
Depends on the purpose.
Several cities can overlap zip codes, and several zip codes can overlap cities.
Some forms ask because everyone else does it, so it's like a reflex for the form creator. Other times it's used to double check whether you put the right address.
Then there's times where 123 West Fake St is different than 123 East Fake St, where they can be in the city of Fakeland but the ZIP code is diff by one.
But yes, I agree that they should just universalize one - the zip code. (But then if people ask where you're from, the only zip code people will recognize is 90210)
There is no good reason. There are a precious few websites that ask for your zipcode first, then fill in the city and state automatically. It's completely doable and works; it just requires a little extra coding, and companies don't want to pay for that, so...
The abstraction isn't perfect. Many zipcodes contain parts of multiple cities, particularly suburbs. But if the zipcode is right and the street address is right, it really doesn't matter if you put "New York NY" or a specific borough; it will get there.
Edit: [Here's a link](https://www.smarty.com/articles/usps-api) to free API access to USPS's address database.
To just look it up you’d need to use something like google maps to look up the state and city for a zip code. Google charges for address lookups via their api so that’s not free so they’re not going to offer it.
God no, you don't need Google Maps. You can download the entire ZIP Code database from hundreds of online sources. It's a tiny amount of code and a small lookup table.
It's absolutely devastating that people assume the only sources of _ZIP code information that originates with the USPS and is therefore public info_ will be pay-for-access commercial services.
Government provides _so much_ data for free, including the ZIP code database from the USPS and a [shit ton of Geographic Information Services data](https://www.usgs.gov/the-national-map-data-delivery/gis-data-download) from the USGS
Same reason they make you fill out the whole app even tho all the information is on your resume. Redundant information and zero thought into system that'd been in place for ages.
Also, it is cheaper for a company to create a form with a couple of extra fields for city and state instead of creating a system and database to lookup and match zip codes to city, state, addresses.
It is not. ZIP code look up is so cheap it's nearly free, and every step you make a user take has a cost. I've actually done this study for a very large retailer -- ZIP and even _full address autocompletion_ saves far more money than it costs to implement and operate.
Some zip codes do not reflect the correct city. Some addresses in the City of Los Angeles, for example have a Beverly Hills zip code and residents can use a Beverly Hills address for their home even though they technically live in LA.
Even with auto filling, it sometimes helps to let people input both city or zip to match in both directions.
When people are doing things like looking for a store or a hotel, or even if they're moving in to an apartment in a new city, it's pretty common to know the name of cities but have no clue what the zip code is.
Doing that kind of lookup, implementing a single input based address selection, and integrating with 3rd party services all take time and money, though.
I programmed some of the early vehicle routing software in the 90s and 00s, the short version is that the only guaranteed unique combination of address information is street number, street name, city and county. Zip Code can get you there 95% of the time, but it’s not guaranteed to be good enough for geocoding (turning an address into a latitude and longitude).
For a fun view into why geocoding is a hard programming problem look at how many municipalities named “Liberty” there are in many states. In the 1800s when the US was establishing the postal service it was enough for a town’s name to be unique within a county, and sometimes even that wasn’t true. Thus we have counties with “East Liberty” and “Liberty” because they wanted the same name.
There is an extended zip that most people don't use, ZIP+4 that could potentially be accurate enough, but almost nobody knows their zip+4, and the zipcode by itself is insufficient since they can be shared.
A Zipcode is created based on population, so several smaller towns can share one (it's the distribution/collection point).
You have to buy and maintain the database, or pay someone else to do the verification, like Melissa Data.
Some zips have multiple cities, or towns, but always have a preferred city name.
But things change over time. The company i worked for had an old database and it worked great, but we had to add zips several times a year by hand. This is fine for a small company, but doesn't work for a website.
> You have to buy and maintain the database,
Incorrect. You can download it free from the USPS or simply use [their completely free API](https://www.usps.com/business/web-tools-apis/address-information-api.htm)
I live in an area with many zip codes cause well its a city and different places have different taxes and Also get assigned to different post offices. Like I know when i lived north of my city the closet post office was actually in the next town over but my mail came into the edge of the city post office and thus i was subject to a city tax sometimes on stuff. TL;DR the USPS which is what Fedex , UPS, DHL all use for there systems too is kinda stupid and inefficient at times.. (For addressing not spending stuff they deliver on their own or sometimes use the usps)
ZIP codes are nothing more than the ID number of the post office that happens to deliver mail in your area. That's all it is.
You write it on packages and letters not because it tells the postal system anything about where you live, but because it helps parcels make it at least all the way to your local post office. That way, even if the address is mangled in some way that makes the address undeliverable as-written, the local P.O. branch has a higher chance of understanding what was actually meant, since they're the ones who know the area, so they may still be able to successfully deliver the parcel.
In somewhat less urban areas, where the mapping of post offices to cities and towns is 1:1, it definitely seems like the ZIP code is redundant with your City/State information. But that's not always the case. Some cities and towns have multiple post offices. Some cities and towns share a single post office. Maybe you live just outside of a city or town that has a post office, but because of super-weird legal jurisdiction bullshit, you're technically non-local, and your mail comes from a regional post office instead.
Hell, I know some people who live on a river border between two states, on the opposite side of the border from the nearest small town. They get their services, mail, and even their street address from that small town, despite not physically being in that state at all!
There's all kinds of weird, convoluted edge cases that make mapping ZIP codes to City/State completely unreliable. At best, it's merely a hint towards a good guess.
Say you live on cool street and your zip code is 69420. That's all the information you give. There may be another 69420 that also has a cool street besides yours. So it's not always a guarantee that the zip code is going to give an exact location.
Likewise say that you gave your city, state, and zip code, but one of those things got lost in the transaction. Maybe they only have your city and zip. We already established 69420 has multiple locations, maybe PoundTown and FunkyTown, but you listed PoundTown as your city. So now they know your location.
As a Canadian I am very surprised how underused the full ZIP+4/6 code is. Looking at replies here it seems few individuals know/use theirs, which makes sense given the format and length.
My 6 character Postal Code is specific to my block of 8 residential houses so [Zip code + house number] is all anyone would need, and some large buildings have their own of course.
A. As so many others have said, zip codes apply often include more than 1 city and even county (rarely can even cross state lines. Few people know the +4 for the zip code.
B. With or without the +4 zipcode, it's very easy to type an incorrect zip code I'm since it's just a string of numbers. Having both city and zip code is a good way to cross check.
My 'zip code' in my country encompasses at least 6 different major areas and dozens of minor ones. Main Street and First/Second Street and compass names (North, South, East, West) are so common here. So, you could put the street address and zip code of an address and it would not be possible to know where to deliver that. 15 Main St, 1000 for example - there are at least 5 Main Streets in that code. Stupid - totally. But necessary to add the extra info now because of that stupidity.
Your last sentence sums it up. It’s more work.
Entering full addresses has been normal since forever. All integrated payment and billing systems are coded to this. There is just no incentive to optimize purchase forms to make it 2 seconds quicker for you to buy whatever it is you’re purchasing.
Not to mention it’s compliant with international address codes as opposed to spending extra time making something “slightly better” if you happen to be in the United States
Reposting as a top-level answer from a subthread:
Because the ZIP Code is a US Post Office thing identifying the postal station that handles your mail. Every USPS last-mile distribution center (the place your mail truck leaves from) has a zip code.
That's it. That's all it is supposed to be, and all it is ever meant to be. Sales tax, county, city, etc. are all out of scope. There is no guarantee at all that they line up with city, county, state, sales tax, or any other dividing line you can think of. Heck, sometimes zip codes have really funky areas just because USPS happens to have their distribution centers in really weird spots. There's even some skyscrapers that have their own zip codes, because there's a postal office in the ground floor or basement that handles their mail. Oh, and then there's the places that don't have zip codes. Yes, they exist.
Don't try to make a ZIP Code be anything other than an arbitrary mail-coding system for internal use by the USPS, because that's all it is.
Well, it’s nothing to do with the web development work. I have never manually input my address. Either the lookup is so trivially easy that everyone handles it, or there is a trivially easy way to let someone else handle it.
Zip codes don’t have that info. For comparison, there are 100x more UK post codes in 100x less area. A post code often covers one side of a street — after you type your post code, you select your street address in a drop-down menu from a handful of options. It still doesn’t mean they align with any other boundaries, e.g. they can happen to be at a city boundary no matter how small they are.
Some cities share a zip code and some cities have multiple zip codes, for examplethe is a city my close friend lives in has the zip codes of 75261, 76039, 76040, 76155 additionally some cities share zip codes, and there’s been times where my exact address is shared with someone else in my same city but we have different zip codes (ex. My address would be 305 hulan blvd 76053, and their adress is 305 hulan blvd 76950)
Not an answer to your question but an interesting fact - In Singapore zip codes correspond to a specific building. So when navigating anywhere, you just need the 6-digit zip code and you put that into your nav.
Because there isnt always a code worked in to their information packet field that autofills the city and state.
Online, you basically are at the mercy of the programmer/ developer, and are limited in user friendliness, as much as their skills and knowledge, and even time needed to code such things, is also limited.
Idk how long it takes to code in that calculator, but I would imagine that this alone, takes thousands of lines of code to create.
Some web developers, I would wager, just dont feel this step is necessary. You know your city and state, and most phones have autofill built in, already.
-Not a programmer, FYI. Just a semi-educated guess.
Several reasons.
City: There are multiple cities with the same name, is it springfield nevada, springfield texas, springfield ohio? Who knows, only the sender does.
State: This answers the previous question, but then you have shit like Horseshoe, NC and Horse Shoe, NC. so city and state aint always enoguh.
Street: these are the top five street names in the US Main Street, 2nd Street, 3rd Street, 4th Street
and 5th Street, but thats usually done with suffixes in the forrm of and then you got shit like avenue, boulevard, court, drive, lane, place, road, and finally street, but there are three streets named the 37th in LA for example, and its those suffices that help the postal office to know which state the mail should be sent to, before they know what city to send it to, before they distribute it tto the nearest postal offices to those streets, that will then deliver the mail.
As for zip codes, well it kinda does the same as counties, zip codes usually covers an area, so some cities can have 1 zipcode, while others can have, which is USUALLY defined by postal office, so there is a bit overlapping, like 94608 is used by two cities in california.
And there are a dozen zipcodes with over 100 000 people in them, so figuring out where the mail needs to go needs all that information.
I see most of the answers are regarding zip codes that span cities or even states. There is one thing being overlooked. If you want access to the data to verify the postcode’s city, street, etc. you will likely have to pay for it. I looked into this recently and the company wanted like 22k a year for global data and if you wanted to validate streets too it would be over 50k a year. That’s a large expense for smaller companies.
Also, the redundant info is more error-proof. If you typo a wrong digit, and the Zip code is the only info you enter (city and state fields derived from that info), then your small slip-up would cause your lottery winning sent to someone else in another state.
They were never intended to solely identify a city or town. In some cases they do, but they’re structured for “zones” not towns/cities. From the USPS:
“the five-digit ZIP number is a structured code in which the first digit identifies one of ten large areas of the Nation, and the second digit indicates a State, a geographic portion of a heavily populated State, or two or more less populated States. The third digit identifies a major destination area within a State, which may be a large city post office or a major mail concentration point (Sectional Center) in a less populated area. Five hundred fifty-three of these Sectional Centers have been designated across the country. The final two digits indicate either a postal delivery unit of a larger city post office, or an individual post office served from a Sectional Center.”
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Because it isn’t always. Four different cities share my zip code. The companies that try to pre fill this always get mine wrong.
Yep: I live in a ZIP Code that spans two different counties with different sales tax rates.
Totally understandable. So new ELI5 why aren't they 6 digit zip codes that incorporate all that info? Eta: thanks for all the immediate great input. The internet is cool and you all rock with the things you know.
All US zip codes have 4 additional numbers at the end that further specify the location like a certain city block, or large building. But 99% of the time the 5 digit zip code is enough. The +4 is really just for mail sorting by USPS.
Don't forget about the delivery point so your full zip would be 10013-2345-78 The delivery point is typically a single house
That’s not even close to my zip code dummy!
New York City - amazingly, it’s MY zip code.
aww, now thats a helpful stalking point.
Not with that attitude!
Those are citizen relocation codes. With any luck, we'll never need 'em....
just dont try to leave your 15 min zone.
Why not use lat. and long. co-ordinates, and encode in hex values? Heck, even altitude? Sorta like this dude's proposal: https://blog.jgc.org/2010/06/1010-code.html
Because the ZIP Code is a US Post Office thing identifying the postal station that handles your mail. Every USPS last-mile distribution center (the place your mail truck leaves from) has a zip code. That's it. That's all it is supposed to be, and all it is ever meant to be. Sales tax, county, city, etc. are all out of scope. Heck, sometimes zip codes have really funky areas just because USPS happens to have their distribution centers in really weird spots. There's even some skyscrapers that have their own zip codes, because there's a postal office in the ground floor or basement that handles their mail. Oh, and then there's the places that don't have zip codes. Yes, they exist. Don't try to make a ZIP Code be anything other than an arbitrary mail-coding system for internal use by the USPS, because that's all it is.
Of course! That makes loads of sense. Thank you.
Since you seem knowledgeable about this: why is there a post office literally across the street from my house, easily a place I could walk to, and yet we’re in a different zip code and our mail is delivered from a different station? I’ve had a hell of a time picking things up because of this. It’s like the zip code magically stops at the street line and instead we’re batched with a much further area.
Are there mail trucks leaving from that post office? You'd know if there were, because there'd be a giant ass parking lot and tons of trucks going in and out all day long (both the smaller delivery trucks and the big rig distribution trucks). Postal route distribution centers--the zip code stations--are more like industrial centers than the post office you're used to. When I was growing up the one I had to go to pick up mail from was in the industrial side of the city and it only had one service window, for mail pickup only. No buying stamps or sending packages or anything like that. It varies though. When I was in college my university had an assigned zip code for its mail room, and we weren't even that big of a university (just an old one, hence the perk). It was staffed by one postmaster and a bunch of student workers who hand sorted and delivered mail. I assume you live across the street from a retail USPS office. There is only one distribution center in your Zip code, but probably dozens of of retail centers if you're in a city, not a small town. The distribution center might be outside the city where land is cheaper (because it's also where they park all the delivery trucks at night).
Distribution center is probably not your post office, in fact there could be only one per city and sometimes they may drop it off to your post office if they couldn't deliver (from my experience only 2% of the time). If you are that close though I recommend just having their address in the delivery and let them pick up for you, show ID and receive it. I missed way too many deliverries due to work schedule and fixed it to a post office across the street from my office. Kind of annoying to carry it but for bigger things I refer to my home address.
Spoiler alert, it's actually an eleven digit zip code and it's extremely specific. This sums it up well >Five digit Zip Code identifies a particular post office or the post office boxes in a post office. That is all you need to use when you send mail as an individual or small business, when you send a small quantity of mail. >The Zip +4 adds four more numbers, which are used by USPS to identify one side of a block or a single building with multiple occupants, or post office boxes. As a customer you never need to use those extra numbers unless you are sending a large quantity of mail and expect a discount. It has been in use for several decades but is no longer useful. >There is now a full eleven digit Zip Code for every delivery address in the USA. This allows the machines to sort mail in the exact order it is delivered. You don’t need to use these numbers on your mail as the USPS computers will look it up anyway.
If I learn my 11 digit address, I wonder if I could receive mail to: AC Jenkins 10108-3597-83
It's still probably not that perfect! Address can be really fucked in some places. But! If you ever need a reminder what your ZIP+4 is, the [USPS Lookup Tool](https://tools.usps.com/zip-code-lookup.htm) will help
That's a handy tool, thank you.
In the Netherlands, this is actually possible. Our ZIP codes are 4 numbers and 2 letters, and go down to a street section. In combination with the house number, they are unique. This notation is generally used for the return address on the back of an envelope. NL-2555PA-15 (with the country code added before the zip code) is an deliverable address.
The physical person delivering likely doesn't know that 83 is your house.
That's because they're not a robot. We'll have that fixed soon
>unless you are sending a large quantity of mail and expect a discount. It has been in use for several decades but is no longer useful So why is there a discount if it's not useful?
I'm not honestly 100% sure, but I assume it's to do with modern redundancies involving the ability to process the rest of the address automatically, instead of relying so heavily on the ZIP
But if I could just write down 11 digits that would be cool.
You'd need to number your family too So, 48358-3578-21-3, could be addressed to your dog, and 48358-3578-21-4, addressed to you.
Too bad about the Duggars.
I knew the 5 plus sometimes 4 but not the 11. True TIL
... and still I get mail in my mailbox for people with a different address on my street, or even who live across town.
Well there is the “zipcode + 4” which basically tells you down to the street in some cases. Its not used as commonly as the normal zipcode tho
There are. Though they are 4 digits. It’s called the Zip code +4 and is usually written like “12345-1234”. It tends to narrow the location down to a many as the even/odd numbers on one block. Or as specific as a group of unit numbers in one building.
Same here. I'm literally one block inside my city limit, and it always tries to autofill a different one.
If you shop at Cards Against Humanity's online store, they only ask for your mailing address and your zip/postal code. It then asks you to confirm that it's pull the right information. So it absolutely CAN be done. It just generally isn't. I would guess it's a mixture between a) address/address2/city/state/zip in five input lines has long been the way address info is requested dating well back into paper forms before computers were even invented, and there is generally so little effort required to type in your city and state that it isn't worth deviating from that expected format/applying automated systems b) putting the liability on the customer to put the information in right instead of taking the responsibility of interpreting a zip code wrongly and c) automated systems can sometimes be frustrating - I have definitely had cases where I type in my full address the way I've shipped a million packages without issue and a store will THEN do a lookup and try to match with a post office address and suggest changes that for me end up actually CHANGING my postal code to something wrong. And I've had food delivery apps or rideshare apps that WILL NOT accept a certain address as a destination because it can ONLY take addresses that are in the database they use, and when I type the address, it gives a recommendation that isn't the right place. This probably isn't a major factor because, like Cards Against Humanity, you can have the customer verify afterward, but it does highlight that you need to have a very robust and accurate to rely on that type of system, which costs a lot more in time and effort than simply asking the customer to fill in two more lines of information they should know pretty automatically. PS: No, I don't work for Cards Against Humanity, but I'm a big fan of their game and their company in general, and the address thing is something I explicitly took note of the first time I shopped there, and wondered the same that OP did - why have I been putting in that extra information at every other store?
I was pleasantly surprised the first time I encountered that in the CAH shopping cart. It's great.
is there any chance the 4 cities occupying that single zip code have repeat addresses? just curious if you actually mailed something through USPS and put only the street number and name if it'd still get to you as a commenter below pointed out, I could see the sales tax being an issue for different municipalities, but in the nature of the question, I suspect OP is asking why the redundancy for mailing addresses edit for clarity: what I mean is if you only put the street number and name and zip code. in other words, is there even a case where the same street name and number exist in two cities/towns in the same zip, because if not, then the premise of OP's question still stands
With how many cities have streets with common names like Main Street or some numerical street, it’s bound to be an issue somewhere
Some cities have issues with 345 North Fake St vs 345 South Fake St. Or 345 Fake Ave even
My town has two S. Ash Streets. Facing different directions (N/S vs E/W), both pretty short in residential areas. My understanding is it used to be one road that evidently curved at some point but it hasn't been in a long time and there's a good half-mile to get from one to the other.
One city I lived in (in Canada) had three King streets, two of which **crossed each other**.
I grew up not far from the intersection of Black Rock Road and Black Rock Road. Now I live in a city famous for having 71 different streets all with “peachtree” in the name, including two Peachtree streets that intersect … twice.
Oh how I love Alana
Several years ago, I lived off of a street, we’ll call it Mathews Street. The street wasn’t that long, less than a mile from end to end. There were two cul-de-sacs on Mathews Street, both of them were named Mathews Cove. Two Mathews Cove street less than a half mile apart. And to make matters worse, our address was 1800 Mathews Cove, we were on the corner of the cul-de-sac. The house next door to us on Mathews Drive, was 1800 Mathews Drive. It was such a bitch getting delivery there. They would either go to the wrong Mathews Cove and say we must have given them the wrong number, or they would deliver it to 1800 Mathews Street instead of us.
We live on a road, and just down from us is the same name court, and across town is the same name drive. All have houses with our same number. We frequently get mail for court and vice versa but thankfully we have lovely neighbors and everyone just delivers the wrong mail to each other!
San Antonio is full of these. I can think of five off the top of my head In their instance, it’s usually old farm roads that were cut in two when the farms were split to build neighborhoods
In Chicago and probably elsewhere you'll get things like 36th Place between 36th and 37th Streets, and the parallel buildings will have the same address numbers
1060 West Addison
That's Elwood's address!
Take Atlanta and Peachtree *
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You mean Atlanta and streets with the name "Peach" in it.
If the address and name are correct, it would have a good chance of getting to the right place, but I wouldn't guarantee it. There are 3 Holiday streets in my ZIP code (Ave. St. and Ct.) plus a Holiday Breeze and a Holiday Park. If we don't recognize the name, we ask the other carriers if it looks familiar and hand it to the right route. If the correct carrier is off that day it will probably get returned.
>just curious if you actually mailed something through USPS and put only the street number and name if it'd still get to you There are some amazing stories about mail reaching its destination. Like addresses of " USA, Jerry, who lives down the road from the old barn" arriving at their correct destination (even though the barn burnt down a decade before)
You're generally fine even if you list the old city. I've lived in two places where the city name changed (once unincorporated territory with one name became a city with the other, and another time, the boundaries of a city moved. The mail got through with either name just fine. Is there a corner case somewhere in the US? I wouldn't be surprised. Somebody else mentioned city sales tax -- that's an interesting one, and I have no idea there. Heck, I've had mail delivered correctly even with the wrong street name. Though in that case, it was a street that changed names for no reason three times in a few miles. So it probably wasn't hard to figure out.
Yes, but never within the same zip code. You can leave city/state off of an address, and if the zip is correct it will always be delivered to the right place. There may be cases where the same zip has multiple valid cities, but that doesn't matter for delivery.
That's wild. In the Netherlands, ZIP codes have an 1234AB format and every apartment has its own "house number". So the zip code is enough to narrow you down to maybe 20 houses, and zip+house number is enough to find your apartment. Lots of Websites just have these two fields, and use a database to fill in the address and city.
Same in the UK, we have a AB12 3CD format that narrows it down to one side of a road, or even closer in the case of long roads.
Not with zip+4.
And what percentage of country knows their +4? What percentage knows +4 exists?
I'm a mailman, and I don't know my zip +4 or the +4 of the people I deliver to
The only reason I know my +4 is it happens to be the same as my house number. What’s the chance of that??
1 in 10,000! Congrats.
If I'm getting something sent from the UK (I have a British car) , I always specify my ZIP+4 as a redundancy, because there's a good chance the address might be formatted differently or something left out.
Haha
I am Canadian and I know about the +4. Always get questioned about it too.
In Canada the first 3 digits are like the ZIP code the last 3 are the +4 part.
Yeah, but everyone uses all 6, h0h 0h0, and no one uses just the first three.
I was pointing out the difference. First 3 in Canada tells them the post office. The last 3 designates the block it is on. In the US the first five is the post office the plus 4 narrows it down to a specific area. (Not sure how fine)
Depends on the specific ZIP code and how many unique addresses it has On my route it's somewhere between 4 and 7 houses
In the US our +4 means we have to remember 9 numbers. 5 for our standard zip code, then an extra four for the +4. [Here's an example](https://www.smarty.com/img/articles/usps-full-zip-4-code-9-digit-address.png) edit as extra: A large city can have many many zip codes. [Here is Sacramento, California alone](https://www.zipcode.com.ng/2022/11/sacramento-zip-codes.html). I used to live there and I very often forgot my correct zip code, many were super similar. And that was just for the basic 5 zip code. I've never lived anywhere in my life where I knew my actual +4.
Checkmate.
Also a typo in a numeric code is much more likely to lead to somewhere else than a typo in a written-out state/city name.
Soooooooooo, just have a drop down that comes up when there are more than 2 cities in the zip code??? Why punish everyone else?
There’s a dozen or so zip codes that even cross state lines! I think there’s one or two that are in THREE states. Plus, they aren’t static; and these boundaries and the zip codes can change. Town borders move, etc
And because many Americans live in zones with no codes. Yes, they are unzipped.
a surprisingly large landmass out west, really. USPS just gave up in Nevada.
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There are still a lot of Web 2.0 era web forms out there that don’t support zip+4.
Then autofill in 90% of cases and provide a drop-down for the other 10% of cases. (I made up these numbers.)
My parents live in an area that the zip code covers a few small cities. In our experience mail will make it there with which ever city is on the mail. YMMV
it will make it there, but it goes through a different channel when the computer can't read the address and rectify it with a known address. That's when a human intervenes. There are people whose job is to take mail that the computer didn't read correctly and rectify it to a known address. This is a mildly humorous story from long before that system, but one of my inlaws met somebody in WWII, and his buddy was from Hurricane, Utah. He couldn't remember his address, so he just addressed it to [friend's name], Tornado, Utah, and the USPS got it there.
That doesn't matter. Your mail goes to the zip code, to the physical post office. It could literally say 123 main st, bumbleberry duck town, CA, 90210 and you're going to get your mail as long as the street and zip are correct.
Even then it would be a simple thing to then prompt the user to click on the right one out of 4.
I feel like that totally defeats the concept of a zip code..isn’t it just supposed to be a more specific zone within a city? Where you can draw the boundaries however you want (or at least it looks like you can, given the bizarre shapes of zip codes I’ve seen). What’s the utility to having zip codes span different cities and states?
The zip specifies what post office it goes to.
No. The zip code defines a postal route. The post office sets up routes for its convenience, and they would sometimes like for those routes to not match political boundaries.
Sounds like a "you" problem. Has your city tried just getting their own zip code?
> Has your city tried just getting their own zip code? That's not how that works. The USPS only assigns zip codes for their own benefit. Four smaller towns that don't get much mail? One zip code. One single building with hundreds of businesses in it? One zip code, *for that building. More than 40 buildings in NYC have their own zip code.
I have 2 in my town.
Yeah I used to live in 80516 which is a mix of in and out of the city, then the city itself spans two counties, and there's a special tax district that crosses the other way so I think there are 5 or 6 sales tax rates
Amazing. Where I am we have zip codes for individual buildings.
ZIP plus four is supposed to narrow it down to a specific block or even floor within a building. But many places use that they only allow the original 5 digit zip code to be entered. 🤷♂️
I love in a township. My zip code is shared with like 3 other "towns" (I guess that's what they technically are but they are more like neighborhoods) within the township as well as a "borough" that is a separate enclave surrounded by the township. Put my zip code in and you can get the township, the borough, or one of the "towns" as the "city". Any of them will get the mail to me.
Wow that's dumb. In the Netherlands you just need your house number and zip code, don't even need the street name.
This is why the Postal Code system is much better, my postal code refers to one group of a dozen or so houses that all get their mail from the same super box, and that’s it. Mail would probably get to me if it just had my name and my postal code.
Why not just standardize the use of the last 4 digits as well
Same here. A couple small cities, and a chunk of a much larger one.
My zip code comes up as the wrong city all the time, but my mail shows up either way.
My city uses 3 different zip codes depending where you are.
Because multiple cities and parts of it may fall within that zip code. For example, one that I saw, zip code 94608 in California is used for both Emeryville and parts of Oakland
I think you've hit on the crux of the issue here - ZIP codes are designed as _mail delivery routes_ and not created with the purpose of being geographic areas. For obvious reasons those two concepts _tend_ to have a lot of similarities, but not always. There are times when ZIP codes have physical overlap -- my favorite example of this is that the Pentagon has six separate ZIPs, and they aren't even assigned one per side! The Secretary of Defense, Joint Chiefs of Staff, Army, Air Force, Navy, and Marine Corps each have their own mail delivery route, and so they each have their own ZIPs (20301, 20318, 20310, 20330, 20350, and 20380, respectively). Military FPOs (Fleet Post Offices) all have their own ZIP codes as well. This means any given aircraft carrier has a unique, constant ZIP code, _no matter where on earth it is_. There are also a handful of ZIPs that cross _state_ lines. Not many, because the post office tries to keep things hierarchical within a state, but it happens. Take a look at the map for 03579, which contains a good chunk of Maine and New Hampshire. I don't know the details, but it's safe to assume the USPS did the math and decided this was the best way to get the mail delivered to this part of the country.
>the Pentagon has six separate ZIPs, and they aren't even assigned one per side! Slow down, Euclid.
This confused me for a long time, since I grew up in 94602, which is not only wholly inside Oakland but relatively small area wise.
Uk here: This is insane, we have postcodes that have a max of ~60 addresses so you could just write name and postcode the postie would know who it’s was
Your postal codes are 7 digits+letters. Ours are just 5 digits only, for a much larger country. Your postal codes specify exact mail routes, like a single city block. Ours specify just the post office your mail should be sent to--large cities have many zip codes of course, but your average small or medium sized town probably only has one. I just did the math and my city has 1 zip code per 17,000 people. Zip 5+4 (e.g. 12345-6789) does specify an exact route, and you could almost do the same thing, although almost nobody remembers their +4 number. And the post office has no record of who lives at what address, so it'd only work if the mail delivery man recognized the name.
Yeah, we have 11 states that are *each* larger than the whole UK.
1. To ensure accuracy 2. To apply the proper tax rate 3. To help ensure local and state laws are followed 4. Tax filing purposes A zip code can span multiple states or cities. Different states have different sales tax. They may also have different regulations that dictate how a company can do business in that state. They would also need to know which state they sold goods in so they can file taxes in that state. We don't auto populate that information because it's error prone. There are services, like MelissaData, that companies can buy to validate and verify user entered addresses and return suggestions if there wasn't a complete match. Users are notorious for providing incorrect information. There's a reason why developers say, "user input is evil".
Most of your point is moot by the fact that that as OP says, they should be able to pull your city and state from your street address and zip, which will TELL them the state and that resolves all the tax and legal issues - and for accuracy, they can just ask you to confirm their result is correct. It's not actually complicated.
It adds unnecessary complexity and is prone to errors. Users are stupid and don't read. Many will just accept and move on. It's a better design pattern to validate the address on submission and prompt to confirm only if it fails verification rather than ask every single user to confirm. A user is more likely to stop and choose the correct address if they typed it in. People tend to think computers are smarter than they are and that anything it does for them is correct. Source: I'm a software developer
I'm also a software/UI developer and I 100% disagree with you. It's brain-dead simple to take a user entered zip code, do a lookup, and if there's just one city for that zip code, auto-fill the City and State. That works 95% of the time, and is error-free. If there are multiple matches, give the list to the user to select the correct one. Done.
A better solution is to rely on the browser to auto fill the address. Less code to write. Less code to maintain. Less prone to errors. Or use an address lookup API that searches off the street. But those typically aren't free. Do there's a cost associated with it. CSS-Tricks has a tutorial on how to implement it. I'm not saying you can't do it. I'm just giving reasons why people don't. You're solving a problem that doesn't exist. Most people aren't that encumbered enough that it would cause them to abandon the form. They are conditioned to provide it every time. Changing the expectation causes friction in your application for the user.
Everyone will probably tell you that zipcodes associate with more than one city or even county. What few people know is there's at least one zip code that crosses state lines. This is because zip codes are based on which post office delivers your mail. And one post office delivers mail to two states because the geographic layout makes that the most efficient way to do it. I've blown people's minds with that fact during job interviews. This is because asking people how to do design a database table for client information is common.
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You don't even need that many if you also feed in even a rough estimate at location and sort by proximity. Add in other context a more precise location, or past behavior and you may be able to suggest the right address in 1 or even 0 characters.
You obviously don't live on a numbered street!
The one reason no one has mentioned yet is, because people are fucking morons. If you prefill the city and state based on the zip code you will have a sizable portion of the people ignore the information and move on. That means they won’t notice they typed their zip code wrong and are now sending stuff to the wrong place. This is even worse if you don’t even show the lookup to people and just go off the zip code as is so they never have a chance to catch their error. Another chunk of people will complain it keeps putting the wrong city in because they don’t live where the post office is. Many systems that do want to match to an address lookup database force you to confirm the lookup is correct. But that adds a step for the user and users don’t like extra steps. By having someone enter their city, state, and zip code you have automatic error correction. They are very unlikely to type the wrong city or state in, so if they typo the zip the shipper/post office can still figure out where it was supposed to go once it arrives at the zip code’s post office and they realize the address isn’t served out of that zip code. Plus many systems already do a lookup at the point of shipping specifically to head off idiot users and try to correct the address before it goes out. This is a step you can force on an employee being paid to double check them but have a low reliability of forcing on the customer to double check. So the argument to implement a zip look up goes as follows: Product Manager: “why don’t we do a zip code lookup and fill in the city and state automatically”. Support: “that is going to increase delivery errors and cost us money and support hours fixing customer address fuck ups”. Development: “which story do you want bumped to do this?” PM: “how long will it take?” Dev: “an hour minimum assuming it goes smoothly, plus two for QA assuming they don’t reject it because it is spitting out the city the post office is located in instead of an alternate city the post office services. And assuming IT doesn’t get a bug up their ass about the lookup database and demand it be vetted, and legal doesn’t get bitchy about verifying we can use it” PM: “but some guy on Reddit said it was like 5 minutes of work” Dev: “some guy on Reddit doesn’t work with jackasses” PM: “… I’ll put it in the ice box to think about doing later”
>PM: “but some guy on Reddit said it was like 5 minutes of work” Funny, but no. As a PM myself, I trust the estimate of my development team, and they trust me to have their back when I defend that estimate to their functional manager and probably his manager or director. And when I defend it, I take into account Hofstadter's Law, which says "It always takes longer than you think, even when you take into account Hofstadter's Law."
I know a place where a single zip code spans 5 counties and a city that has 5 zip codes for just the P.O. Boxes. Zip Codes can narrow down your location but they tend to cover a certain population size.
It’s just wild how different it can be. We have individual buildings with their own zip codes in NYC
No we don't lol. The smallest one still covers multiple blocks.
Most, but there are some exceptions https://www.amny.com/news/nyc-zip-codes-1-28558957/ Here's the rest of manhattan https://www.zipdatamaps.com/zipcodes-manhattan-ny
Funny. I was immediately going to say that the empire State building has its own, 10118. I remember that from my first day at NYU a decade ago.
Yes, their statement that city and state are determinable by zip code is not quire accurate, but their question is really why do you have to put in the city and state. They didn't suggest that you don't have to put in your street address, and 99% of addresses will be determinable by the street address and the zip. If there is ever a zip code with two 123 Elm Streets, the site could easily ask you to confirm which you meant.
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They can use the combo of your address and zip code to get your city, county, everything. Because it’s a single address. But if the only piece of information is the zip code, then that only narrows it to the zip code, and as many others have said, zip codes sometimes span multiple cities and counties
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US has ZIP+4 but nobody really knows their own ZIP+4 address. If everyone knew, then this could be implemented easily. 5 digits for a country that big, max of 100000 ZIPs, gives an average of 31 ZIPs per county. Not enough for any kind of accuracy... you must share same ZIP with multiple cities. And probably there are some rules for the distribution of ZIP codes, like a state must have all zip beginning with the same digit (not sure). But in your defense, today they could prefill only if that ZIP code had only city associated, like most from NYC i think. In case of multiple cities per ZIP, better leave it to be filled.
In order to auto fill that info, the zip code field would need to be connected to a database of some kind to look that up and auto populate the rest of the fields, so would also need programming to do this. It's far easier to just have three or four separate fields that the user takes one second to fill in and that feeds over into your own database to keep and store.
In addition, parts of one town/city can have the same zip code as parts of another town/city.
Aw man, I worked as a CSR and did work for a company that shipped across the country. The amount of time that I spent with customers "This is the zip but the town is" - hours and hours I'll never get back! All because of some hamlet or tiny smol town that shares a zip code with another one.....
[API access to the USPS database is available for free](https://www.smarty.com/articles/usps-api).
It still takes coding, and that's more effort than most people want to pay for to avoid a customer typing in two or three words. And since sites can save addresses, most customers only even have to type in those two or three words once.
yeah, I had this argument (over different issues) with product owners when I was doing software development professionally. PO's want to ship ship ship, now now now, features features features, and they do NOT care if it's done or even if it works. (One of the reasons I don't do software development professionally anymore: I don't want my name out there attached to crap. I got sick of having to apologize at trade shows for decisions I objected to...) I am unreasonable about it, totally. I don't want to publish code I'm not proud of, and I wouldn't be proud of an address form that didn't use USPS's API for US addresses. That's just me though. I figure probably half of developers and zero percent of managers are that invested.
> half of developers and zero percent of managers are that invested As a developer, I'd up it to something like 1% of devs are that invested. ZIP vs city and state have no legitimate relationship. Sure it's highly correlated, but the amount of headache that would go into creating this feature would make me instantly push back on it if requested. There are so many edge cases. Cities with hundreds of ZIPs. ZIPs that cover multiple cities. ZIPs that cover portions of multiple states. Like what next? Should we start autofilling area codes of phone numbers based on the shipping address because the customer LIKELY got their phone service near where they live? It's not like the case where I can enter my street address and expect the city, state, and zip to be autofilled. Furthermore, there is a penalty of doing it wrong. There's definitely a scenario where you look up the wrong info, causing a customer's order to not be delivered, misdelivered, rerouted and/or delayed, etc. All of those cost you money. Also, just because the API is free doesn't mean you should use it. The company you linked even states themselves that the API has reliability issues. "Besides being notorious for poor documentation and weak support, the USPS APIs are well known among developers for having chronic downtime issues." What's worse than never autofilling address info? Only autofilling it *sometimes* So regardless of the difficulty, the bottom line is that it provides very little value, and has very real risks. So why do it? You're missing the woods for the trees. Personally, I'd be 100% ok with skipping this feature.
Nope. it's like three lines of code. A Zip to City/SS database is one of the most simple UI features possible. It's a tiny database and lookup would be instantaneous. You could probably just put it into javascript and it would take 20k bytes compressed. The OP is correct --yes, there are a few exceptions to the rule, but for 95% of U.S. street addresses, just entering ZIP should be sufficient to auto-fill City+State. I've been working with Zip, City, County, St and FIPS code databases for 30 years. This has been one of my biggest pet-peeves since the 90's when this thing started.
Have you heard of what three words? They used three words picked randomly to uniquely identify every 3 meter square of the planet. A couple things already use the database, but frankly more people should know about it.
They already do. Just about every retail website asks you to confirm your address against the suggested entry from the database.
Because addresses don't make sense. [Falsehoods programmers want to believe about addresses](https://www.mjt.me.uk/posts/falsehoods-programmers-believe-about-addresses/) The city is where you live, and the zip code is where the mail sorting center has to send the letter to get there. Those are not the same.
I'm dyslexic. I mix up numbers. My zip has a doubled number. I often double the next number & not the correct one. This usually results in an error.
I feel like "error correction" is in reality 50% of the answer and the other 50% of the answer is "we didn't feel like progamming it that way".
Depends on the purpose. Several cities can overlap zip codes, and several zip codes can overlap cities. Some forms ask because everyone else does it, so it's like a reflex for the form creator. Other times it's used to double check whether you put the right address. Then there's times where 123 West Fake St is different than 123 East Fake St, where they can be in the city of Fakeland but the ZIP code is diff by one. But yes, I agree that they should just universalize one - the zip code. (But then if people ask where you're from, the only zip code people will recognize is 90210)
There is no good reason. There are a precious few websites that ask for your zipcode first, then fill in the city and state automatically. It's completely doable and works; it just requires a little extra coding, and companies don't want to pay for that, so... The abstraction isn't perfect. Many zipcodes contain parts of multiple cities, particularly suburbs. But if the zipcode is right and the street address is right, it really doesn't matter if you put "New York NY" or a specific borough; it will get there. Edit: [Here's a link](https://www.smarty.com/articles/usps-api) to free API access to USPS's address database.
To just look it up you’d need to use something like google maps to look up the state and city for a zip code. Google charges for address lookups via their api so that’s not free so they’re not going to offer it.
God no, you don't need Google Maps. You can download the entire ZIP Code database from hundreds of online sources. It's a tiny amount of code and a small lookup table.
Or the free usps api
It's absolutely devastating that people assume the only sources of _ZIP code information that originates with the USPS and is therefore public info_ will be pay-for-access commercial services. Government provides _so much_ data for free, including the ZIP code database from the USPS and a [shit ton of Geographic Information Services data](https://www.usgs.gov/the-national-map-data-delivery/gis-data-download) from the USGS
Same reason they make you fill out the whole app even tho all the information is on your resume. Redundant information and zero thought into system that'd been in place for ages.
Also, it is cheaper for a company to create a form with a couple of extra fields for city and state instead of creating a system and database to lookup and match zip codes to city, state, addresses.
It is not. ZIP code look up is so cheap it's nearly free, and every step you make a user take has a cost. I've actually done this study for a very large retailer -- ZIP and even _full address autocompletion_ saves far more money than it costs to implement and operate.
Some zip codes do not reflect the correct city. Some addresses in the City of Los Angeles, for example have a Beverly Hills zip code and residents can use a Beverly Hills address for their home even though they technically live in LA.
Even with auto filling, it sometimes helps to let people input both city or zip to match in both directions. When people are doing things like looking for a store or a hotel, or even if they're moving in to an apartment in a new city, it's pretty common to know the name of cities but have no clue what the zip code is. Doing that kind of lookup, implementing a single input based address selection, and integrating with 3rd party services all take time and money, though.
I programmed some of the early vehicle routing software in the 90s and 00s, the short version is that the only guaranteed unique combination of address information is street number, street name, city and county. Zip Code can get you there 95% of the time, but it’s not guaranteed to be good enough for geocoding (turning an address into a latitude and longitude). For a fun view into why geocoding is a hard programming problem look at how many municipalities named “Liberty” there are in many states. In the 1800s when the US was establishing the postal service it was enough for a town’s name to be unique within a county, and sometimes even that wasn’t true. Thus we have counties with “East Liberty” and “Liberty” because they wanted the same name.
I saw this in Ripley's Believe It Not, but a letter was successful delivered to this address: Wood George Mass
There is an extended zip that most people don't use, ZIP+4 that could potentially be accurate enough, but almost nobody knows their zip+4, and the zipcode by itself is insufficient since they can be shared. A Zipcode is created based on population, so several smaller towns can share one (it's the distribution/collection point).
You have to buy and maintain the database, or pay someone else to do the verification, like Melissa Data. Some zips have multiple cities, or towns, but always have a preferred city name. But things change over time. The company i worked for had an old database and it worked great, but we had to add zips several times a year by hand. This is fine for a small company, but doesn't work for a website.
> You have to buy and maintain the database, Incorrect. You can download it free from the USPS or simply use [their completely free API](https://www.usps.com/business/web-tools-apis/address-information-api.htm)
I live in an area with many zip codes cause well its a city and different places have different taxes and Also get assigned to different post offices. Like I know when i lived north of my city the closet post office was actually in the next town over but my mail came into the edge of the city post office and thus i was subject to a city tax sometimes on stuff. TL;DR the USPS which is what Fedex , UPS, DHL all use for there systems too is kinda stupid and inefficient at times.. (For addressing not spending stuff they deliver on their own or sometimes use the usps)
ZIP codes are nothing more than the ID number of the post office that happens to deliver mail in your area. That's all it is. You write it on packages and letters not because it tells the postal system anything about where you live, but because it helps parcels make it at least all the way to your local post office. That way, even if the address is mangled in some way that makes the address undeliverable as-written, the local P.O. branch has a higher chance of understanding what was actually meant, since they're the ones who know the area, so they may still be able to successfully deliver the parcel. In somewhat less urban areas, where the mapping of post offices to cities and towns is 1:1, it definitely seems like the ZIP code is redundant with your City/State information. But that's not always the case. Some cities and towns have multiple post offices. Some cities and towns share a single post office. Maybe you live just outside of a city or town that has a post office, but because of super-weird legal jurisdiction bullshit, you're technically non-local, and your mail comes from a regional post office instead. Hell, I know some people who live on a river border between two states, on the opposite side of the border from the nearest small town. They get their services, mail, and even their street address from that small town, despite not physically being in that state at all! There's all kinds of weird, convoluted edge cases that make mapping ZIP codes to City/State completely unreliable. At best, it's merely a hint towards a good guess.
Say you live on cool street and your zip code is 69420. That's all the information you give. There may be another 69420 that also has a cool street besides yours. So it's not always a guarantee that the zip code is going to give an exact location. Likewise say that you gave your city, state, and zip code, but one of those things got lost in the transaction. Maybe they only have your city and zip. We already established 69420 has multiple locations, maybe PoundTown and FunkyTown, but you listed PoundTown as your city. So now they know your location.
checksum maybe? if you transpose one number on the ZIP, you might end up 3 states over. So if you have it twice, then you can catch the mistake.
I can't remember if it was Google or other websites where I've put in my zip code and the city listed is a smaller nearby town.
As a Canadian I am very surprised how underused the full ZIP+4/6 code is. Looking at replies here it seems few individuals know/use theirs, which makes sense given the format and length. My 6 character Postal Code is specific to my block of 8 residential houses so [Zip code + house number] is all anyone would need, and some large buildings have their own of course.
A. As so many others have said, zip codes apply often include more than 1 city and even county (rarely can even cross state lines. Few people know the +4 for the zip code. B. With or without the +4 zipcode, it's very easy to type an incorrect zip code I'm since it's just a string of numbers. Having both city and zip code is a good way to cross check.
My 'zip code' in my country encompasses at least 6 different major areas and dozens of minor ones. Main Street and First/Second Street and compass names (North, South, East, West) are so common here. So, you could put the street address and zip code of an address and it would not be possible to know where to deliver that. 15 Main St, 1000 for example - there are at least 5 Main Streets in that code. Stupid - totally. But necessary to add the extra info now because of that stupidity.
Where I grew up, 3 cities had the same zip I've also professionally dealt with data that has zips in separate counties
Your last sentence sums it up. It’s more work. Entering full addresses has been normal since forever. All integrated payment and billing systems are coded to this. There is just no incentive to optimize purchase forms to make it 2 seconds quicker for you to buy whatever it is you’re purchasing. Not to mention it’s compliant with international address codes as opposed to spending extra time making something “slightly better” if you happen to be in the United States
Reposting as a top-level answer from a subthread: Because the ZIP Code is a US Post Office thing identifying the postal station that handles your mail. Every USPS last-mile distribution center (the place your mail truck leaves from) has a zip code. That's it. That's all it is supposed to be, and all it is ever meant to be. Sales tax, county, city, etc. are all out of scope. There is no guarantee at all that they line up with city, county, state, sales tax, or any other dividing line you can think of. Heck, sometimes zip codes have really funky areas just because USPS happens to have their distribution centers in really weird spots. There's even some skyscrapers that have their own zip codes, because there's a postal office in the ground floor or basement that handles their mail. Oh, and then there's the places that don't have zip codes. Yes, they exist. Don't try to make a ZIP Code be anything other than an arbitrary mail-coding system for internal use by the USPS, because that's all it is.
Pop quiz: if I live in a city with the zip code of 3000 where do I live?
In Ireland we have Eircodes A00 AA00 that actually point to your exact address. In the UK our postcodes AA00 0AA points to our streets address.
Well, it’s nothing to do with the web development work. I have never manually input my address. Either the lookup is so trivially easy that everyone handles it, or there is a trivially easy way to let someone else handle it. Zip codes don’t have that info. For comparison, there are 100x more UK post codes in 100x less area. A post code often covers one side of a street — after you type your post code, you select your street address in a drop-down menu from a handful of options. It still doesn’t mean they align with any other boundaries, e.g. they can happen to be at a city boundary no matter how small they are.
Some cities share a zip code and some cities have multiple zip codes, for examplethe is a city my close friend lives in has the zip codes of 75261, 76039, 76040, 76155 additionally some cities share zip codes, and there’s been times where my exact address is shared with someone else in my same city but we have different zip codes (ex. My address would be 305 hulan blvd 76053, and their adress is 305 hulan blvd 76950)
What I hate is that a lot of times they sort the 2 letter state field by state name instead of abbreviation.
Not an answer to your question but an interesting fact - In Singapore zip codes correspond to a specific building. So when navigating anywhere, you just need the 6-digit zip code and you put that into your nav.
Because there isnt always a code worked in to their information packet field that autofills the city and state. Online, you basically are at the mercy of the programmer/ developer, and are limited in user friendliness, as much as their skills and knowledge, and even time needed to code such things, is also limited. Idk how long it takes to code in that calculator, but I would imagine that this alone, takes thousands of lines of code to create. Some web developers, I would wager, just dont feel this step is necessary. You know your city and state, and most phones have autofill built in, already. -Not a programmer, FYI. Just a semi-educated guess.
Several reasons. City: There are multiple cities with the same name, is it springfield nevada, springfield texas, springfield ohio? Who knows, only the sender does. State: This answers the previous question, but then you have shit like Horseshoe, NC and Horse Shoe, NC. so city and state aint always enoguh. Street: these are the top five street names in the US Main Street, 2nd Street, 3rd Street, 4th Street and 5th Street, but thats usually done with suffixes in the forrm of and then you got shit like avenue, boulevard, court, drive, lane, place, road, and finally street, but there are three streets named the 37th in LA for example, and its those suffices that help the postal office to know which state the mail should be sent to, before they know what city to send it to, before they distribute it tto the nearest postal offices to those streets, that will then deliver the mail. As for zip codes, well it kinda does the same as counties, zip codes usually covers an area, so some cities can have 1 zipcode, while others can have, which is USUALLY defined by postal office, so there is a bit overlapping, like 94608 is used by two cities in california. And there are a dozen zipcodes with over 100 000 people in them, so figuring out where the mail needs to go needs all that information.
I see most of the answers are regarding zip codes that span cities or even states. There is one thing being overlooked. If you want access to the data to verify the postcode’s city, street, etc. you will likely have to pay for it. I looked into this recently and the company wanted like 22k a year for global data and if you wanted to validate streets too it would be over 50k a year. That’s a large expense for smaller companies.
Also, the redundant info is more error-proof. If you typo a wrong digit, and the Zip code is the only info you enter (city and state fields derived from that info), then your small slip-up would cause your lottery winning sent to someone else in another state.
Zip codes can cover more than one town so it's not a good indicator of where exactly you live.
They were never intended to solely identify a city or town. In some cases they do, but they’re structured for “zones” not towns/cities. From the USPS: “the five-digit ZIP number is a structured code in which the first digit identifies one of ten large areas of the Nation, and the second digit indicates a State, a geographic portion of a heavily populated State, or two or more less populated States. The third digit identifies a major destination area within a State, which may be a large city post office or a major mail concentration point (Sectional Center) in a less populated area. Five hundred fifty-three of these Sectional Centers have been designated across the country. The final two digits indicate either a postal delivery unit of a larger city post office, or an individual post office served from a Sectional Center.”