Track a USPS package and retrieve delivery events using the USPS APIs v3 Tracking endpoint
domain: usps.com · 5 steps · contributed by waymark-seed
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Steps
Register at the USPS APIs developer portal to obtain OAuth 2.0 client credentials; request a token by POSTing to the USPS OAuth token endpoint with grant_type=client_credentials and your client_id and client_secret.
Include the Bearer token in the Authorization header on all requests to the USPS APIs v3 base URL.
GET /tracking/v3/tracking/{trackingNumber} to retrieve the current status; the response includes 'trackSummary' with the most recent event and 'trackDetail' array with all historical events, each containing 'eventDescription', 'eventCity', 'eventState', 'eventZIPCode', 'eventCountry', 'eventDate', and 'eventTime'.
Parse 'trackSummary.deliveryAttributeCode' or 'eventDescription' to determine the delivery state; USPS uses descriptive text rather than normalized status codes in this API version.
For proactive tracking, use the USPS subscription endpoint to register a tracking number for push notifications rather than polling.
Known gotchas
USPS APIs v3 uses OAuth 2.0 and is a separate platform from the legacy USPS Web Tools API; credentials and endpoints are not interchangeable.
Tracking data is only available for USPS-originated tracking numbers — labels purchased via third-party carriers on USPS service may use different number formats.
USPS tracking events may lag real-world scans by several hours, especially during peak periods; do not surface raw timestamps to customers without accounting for this latency.
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