application/x-7z-compressed

The 7-Zip project's own container, built around LZMA when zip's Deflate was showing its age — it still posts some of the best ratios for large software archives, and it encrypts file names as well as contents, which zip's classic crypto never managed. The type was never registered with IANA; application/x-7z-compressed is simply the label the ecosystem settled on, so expect application/octet-stream from servers that never heard of it. The format is documented by its LGPL reference implementation rather than a standards body.

Defined by 7-Zip — 7z format. Registry facts from the IANA media-types registry via mime-db.