USPS Web Tools API retired — Python migration to v3 REST

[jtalk22]

USPS permanently shut down the Web Tools XML API on January 25, 2026. The endpoints this package calls (secure.shippingapis.com/ShippingAPI.dll) no longer respond, so address validation, tracking, and all other operations fail.

The replacement is the USPS v3 REST API, which is a fundamentally different architecture:

• Auth: OAuth 2.0 client_credentials grant (replaces the old user ID)
• Format: JSON request/response (no more XML)
• Rate limits: 40–60 requests/hour (was effectively unlimited)
• Credentials: Consumer Key + Consumer Secret from developer.usps.com

The OAuth token lifecycle is tricky — tokens expire hourly and issuing a new token invalidates the previous one, so concurrent token refreshes cause 401 cascades.

I maintain a Python SDK on PyPI that handles the v3 migration:

pip install usps-v3

from usps_v3 import USPSClient

client = USPSClient(
    consumer_key="your_key",
    consumer_secret="your_secret"
)

result = client.validate_address(
    street_address="1600 Pennsylvania Ave NW",
    city="Washington",
    state="DC",
    zip_code="20500"
)

Source: https://github.com/revereveal/usps-v3 — MIT licensed, 160+ tests.

For anyone who'd rather not deal with USPS OAuth and rate limits, https://revaddress.com provides a managed API with flat-rate pricing.

Migration reference: https://revaddress.com/blog/usps-web-tools-migration-checklist

[ELY3M]

not paying $29 a month!!!!!!!