Add ZIP+4 to Addresses via API
Append ZIP+4, carrier routes, and a full set of USPS data fields to addresses or coordinates — programmatically, at scale.
What is ZIP+4, and why do you need it?
A standard ZIP code is five digits. ZIP+4 adds four more digits to the end, separated by a hyphen, and those four digits are doing a surprising amount of work.
The first two digits narrow the address down to a delivery sector — usually a few blocks or a single large building.
The last two digits narrow it further to a delivery segment — a specific floor, a department, or even one high-volume mailbox.
So 20006 becomes something like 20006-1010, and the USPS knows exactly where to send your mail before it ever leaves the local sorting facility.
ZIP+4 was introduced in 1983, and while it's technically optional, using it speeds up delivery, reduces address errors, and unlocks bulk mail discounts.
For direct mail, address validation, logistics, or fraud detection applications, ZIP+4 is one of the highest-value data points you can attach to an address.
Adding ZIP+4 via the Geocodio API in three steps
1. Create an API key
Sign in to your dashboard and create an API key. Creating one is free. You only pay for the lookups you actually run, and the first 2,500 lookups per day are free.
2. Add the usps_zip_4 field to your request
ZIP+4 works as an append on standard geocoding or reverse geocoding calls. When you add fields=usps_zip_4 to your request, Geocodio returns the full set of USPS data alongside the regular geocoding result.
A quick example:
GET https://api.geocod.io/v1.7/geocode
?q=1600+Pennsylvania+Ave+NW+Washington+DC
&fields=usps_zip_4
&api_key=YOUR_API_KEYYou can see a full example response in our API documentation.
Heads up
You'll want API version 1.5 or higher to use the ZIP+4 field. (If you're already on a newer version, you're fine. We don't deprecate fields just to make your life harder.)
3. Use a client library (optional, but nice)
If you'd rather not write raw HTTP calls, Geocodio has official and community libraries for PHP, Node.js, Python, Ruby, R, .NET, and more. They all support the ZIP+4 append. Just pick your favorite.
Prefer to upload a spreadsheet?
If you don't need an integration and just want to add ZIP+4 to a list of addresses, you can upload a spreadsheet instead. Add ZIP+4 to a spreadsheet →
What you get back with every ZIP+4 lookup
ZIP+4
The 4-digit extension that pinpoints the delivery sector and segment.
ZIP9
The full 9-digit ZIP code as a single string. Handy for systems that store ZIP+4 without the hyphen.
Carrier Route
The specific route a mail carrier walks or drives to reach the address. Direct mail folks live for this field.
Residential Delivery Indicator (RDI)
Determines whether an address is Commercial or Residential.
Record Type
Tells you what kind of address this is: street, PO Box, rural route, highrise, firm, or general delivery.
Building or Firm Name
If the USPS recognizes a business or building at the address, you'll get the name here.
Government Building
A flag that identifies federal, state, or local government addresses.
Valid Delivery Area
Confirms the address is in a valid USPS delivery area. (Yes, mail can actually arrive here.)
City Delivery Indicator
Tells you whether the address is inside a city delivery area, which affects how it gets routed.
Facility Code
The USPS facility code, useful if you're tracking sortation or working with bulk mailers.
Exact Match
Whether the address matches the USPS's authoritative database exactly. Great for confidence scoring.
ZIP+4
The 4-digit extension that pinpoints the delivery sector and segment.
ZIP9
The full 9-digit ZIP code as a single string. Handy for systems that store ZIP+4 without the hyphen.
Carrier Route
The specific route a mail carrier walks or drives to reach the address. Direct mail folks live for this field.
Residential Delivery Indicator (RDI)
Determines whether an address is Commercial or Residential.
Record Type
Tells you what kind of address this is: street, PO Box, rural route, highrise, firm, or general delivery.
Building or Firm Name
If the USPS recognizes a business or building at the address, you'll get the name here.
Government Building
A flag that identifies federal, state, or local government addresses.
Valid Delivery Area
Confirms the address is in a valid USPS delivery area. (Yes, mail can actually arrive here.)
City Delivery Indicator
Tells you whether the address is inside a city delivery area, which affects how it gets routed.
Facility Code
The USPS facility code, useful if you're tracking sortation or working with bulk mailers.
Exact Match
Whether the address matches the USPS's authoritative database exactly. Great for confidence scoring.
What you get back with every ZIP+4 lookup
Related Resources
API Documentation
The full reference for the ZIP+4 endpoint and every other field we return.
Complete Guide to ZIP Codes
Everything about ZIP codes, ZIP+4, and the history of postal sorting.
Add ZIP+4 to a Spreadsheet
Don't need an integration? Upload a spreadsheet and add ZIP+4 to a list of addresses instead.
Unlimited Geocoding
Process up to 5M lookups per day for a flat rate, all data appends included.
By the time you finish reading this page, the Geocodio API will have processed 5.3 million lookups.
Your data could be next...