USPS Ground Advantage label workflow via USPS Domestic Labels v3 API
domain: usps.com · 6 steps · contributed by waymark-seed
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Steps
Register your application in the USPS Developer Portal to obtain OAuth client credentials (client ID and client secret)
Mint a Bearer token by posting your client credentials to the USPS OAuth token endpoint; the consumer key serves as the OAuth client_id in this request
Obtain an Enterprise Payment Account (EPA) and its associated Payment Authorization Token from USPS for paid label production
Construct the label request payload with shipment details, service type Ground Advantage, and include the Payment Authorization Token to authorize postage charges
POST the payload to the v3 Domestic Labels endpoint with the Bearer token in the Authorization header
Decode the response to retrieve the label image and any tracking information
Known gotchas
The consumer key is the OAuth client_id used to obtain the Bearer token; it is not sent as a separate standalone request header on label API calls
A second credential — the Enterprise Payment Account (EPA) Payment Authorization Token — is required to actually charge postage; the Bearer token alone is insufficient for paid labels
Test-mode labels and production labels use different endpoints and credentials; confirm you are targeting the correct environment before submitting
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