application/gzip

A compressor, not an archiver: gzip wraps exactly one stream, which is why it travels glued to tar as .tar.gz. Send application/gzip when the download is the .gz file itself; if you set Content-Encoding: gzip instead, the browser silently decompresses in transit and the user never receives the file they asked for — the classic way to hand someone a .tar.gz that is secretly just a tar. RFC 6713 registered the type in 2012; the older application/x-gzip label still circulates from servers that predate it.

.tgz is the contracted form of .tar.gz — both arrive as application/gzip, the tar inside is invisible to the media type.

Defined by RFC 6713 · IANA registration. Registry facts from the IANA media-types registry via mime-db.