I need an API to give me the zip code of a location when someone enters a location like Los Angeles, California. I have seen many APIs that give you the details by the zip code, but I need the reverse.
USPS has an address information api. You give it an address and it gives you the zip code. And as the commenters said, you need to provide an address, because many cities have multiple zip codes.
Check out the API from SmartyStreets.
As with the USPS address information API (mentioned above), you provide an address, the API provides the verified, standardized address along with the complete ZIP Code (5-digit code, Plus 4 Code, and Delivery Point).
Feel free to experiment with the free demo.
The advantages of this API over the USPS API are numerous. Also, the USPS API is meant specifically "to facilitate USPS shipping transactions only". SmartyStreets utilizes official, current USPS data.
**UPDATE: It's also now free for low-usage users.
***UPDATE: SmartyStreets now offers an address API and a ZIP Code API.
In the interest of full disclosure, I'm a software developer at SmartyStreets.
This Zip Code API provides the following functions:
- Distance Between Zip Code API
- Zip Codes in Radius API
- Zip Code to City and State API and Zip Code to Latitude/Longitude API
- Zipcode based on City and State
They have a cross reference database of zipcode, to lat/long-itude, and the weather station.
I am not aware of anything freely available, you will likely need to pay to compile this
来源：https://stackoverflow.com/questions/7129313/zip-code-lookup-api