Resumable downloads restarting from an offset past the end of a file, usually after the file was replaced by a shorter one.
Why you would test it
The edge case of resumable transfers. A client that resumes from a stale offset lands here, and should restart rather than retry.
What your client should do about a 416
Re-read the current length from the Content-Range header on the 416 response, then either restart the transfer or request a valid range. Retrying the same range is guaranteed to fail again.
416 versus the codes it gets confused with
416 vs 206 Partial Content — 206 is the success case for the same request shape.
416 vs 400 Bad Request — A syntactically invalid Range header is a 400; a valid one that does not overlap the resource is a 416.
Endpoints that return 416
1 endpoint in this playground answers with 416. Every one is free, needs no signup, and can be called from the browser or with curl.