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USPS License
4 posts in this collection.
4 reviewed guides
- USPS v3
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GuideMarch 10, 2026
USPS API Pricing 2026 — What It Actually Costs
USPS address validation stopped being free on August 1, 2026. The published fee curve, the license that gates it, and what direct vs third-party costs.
8 min readOnboardingMarch 10, 2026
How to Get a USPS CRID and MID, and Link Them to the v3 API (2026)
A USPS CRID identifies the business; a MID identifies the mailer. Here is where to find them, connect the EPA, link COP claims, and activate v3 APIs.
16 min readTroubleshootingMarch 10, 2026
USPS v3 OAuth Troubleshooting: Every Error and How to Fix It
401, 403, and 429 from USPS v3, with the exact fix for each, including the Addresses API license that has gated address calls since August 1, 2026.
9 min readMigrationMarch 10, 2026
USPS Web Tools Migration Checklist (2026)
A numbered checklist for moving off USPS Web Tools XML: endpoint map, the license now required, OAuth, field mapping, error mapping, and the cutover.
14 min read