416 Range Not Satisfiable

416 Range Not Satisfiable (formerly Requested Range Not Satisfiable) is returned when the client requests a byte range using the Range header, but the server cannot serve that range because it falls outside the bounds of the resource. The server should include a Content-Range header indicating the total size of the resource.

Relevant in video streaming, file download resumption, and large file serving.

• Resume download requesting bytes beyond the end of the file
• Video player seeking past the end of the stream
• Stale range request after the file was updated (file shrank)
• Off-by-one error in range calculation

• Check the Content-Range header in the 416 response for the actual resource size
• Re-fetch the resource from the beginning if the range is invalid
• Handle 416 in download clients by restarting the download
• Use ETag or Last-Modified validation before resuming