application/x-bzip2

Julian Seward's block-sorting compressor: Burrows-Wheeler plus Huffman, squeezing noticeably tighter than gzip at the cost of speed. Like gzip it compresses a single stream and has no notion of files, so in practice it arrives as .tar.bz2. The x- prefix means it was never registered with IANA — the label is convention, defined by the reference implementation rather than a spec. New systems have largely moved to xz and zstd, but two decades of source tarballs keep the type alive; every stream opens with BZh followed by the block-size digit.

Defined by bzip2 home page. Registry facts from the IANA media-types registry via mime-db.