
Unified parcel tracking API across 60+ carriers worldwide (USPS, FedEx, UPS, DHL, etc.).
WhereParcel API is a free Tracking API that requires apiKey authentication, is served over HTTPS and supports CORS, so it can be called from the browser.
WhereParcel API Documentation
Details from whereparcel.com.

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The WhereParcel API is provided by WhereParcel (whereparcel.com). WhereParcel API Documentation
Yes. The WhereParcel API is listed in the Tracking category of the public-apis directory, which only includes APIs that are free or have a free tier. Check its documentation for rate limits and paid plans.
Yes. The WhereParcel API uses apiKey authentication, so you need to register for credentials before making requests.
Yes. The WhereParcel API supports CORS, so front-end JavaScript can call it directly.
Yes. The WhereParcel API is served over HTTPS, so it's safe to use in production.