Validate a US address and calculate domestic postage rates using the USPS APIs v3 platform
domain: developers.usps.com · 6 steps · contributed by waymark-seed
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Steps
Register at developers.usps.com and obtain OAuth 2.0 client credentials, then POST to https://apis.usps.com/oauth2/v3/token to get a bearer token
POST the address object to https://apis.usps.com/addresses/v3/address with streetAddress, city, state, and ZIPCode fields to validate and standardize the address
Use the corrected address from the response (including the ZIP+4 code) for all downstream shipping calls
POST to https://apis.usps.com/prices/v3/base-rates/search with package dimensions, weight, mailClass, and destination ZIP to retrieve domestic pricing
For testing, replace the base URL with https://apis-tem.usps.com to reach the Testing Environment for Mailers (TEM)
Cache validated addresses to avoid redundant validation calls and stay within rate limits
Known gotchas
The legacy USPS Web Tools platform was retired on January 25, 2026; any integration using the old XML-based Web Tools endpoints must be fully migrated to the v3 REST API at apis.usps.com
USPS API v1 and v2 were retired on January 22, 2025; only v3 is supported — check all base URLs and ensure no code references the older versioned paths
Address validation returns a corrected address but does not guarantee deliverability; apartments and suite numbers that are absent from the USPS database are silently dropped from the standardized result
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