What is a BZ2 file?

BZ2 — bzip2

What is it?

Bzip2 compresses better than gzip — typically 10 to 20% better — at the cost of noticeably slower speed. That's the trade-off it offers: time in exchange for space.

Like gzip, it only handles one file at a time, which is why .tar.bz2 archives pair it with TAR.

History & origin

Julian Seward released bzip2 in 1996, building on an ingenious method that rearranges data to make it more compressible before the actual compression step.

It had its heyday in Linux distributions during the 2000s, before being overtaken by the more efficient xz.

Why it is useful

Better compression than gzip, with an open and well-established format.

It's available on every Unix system without needing to install anything.

Limits & drawbacks

Slow, both when compressing and decompressing.

It's now squeezed between gzip, which is faster, and xz, which compresses better — leaving it without a clear niche of its own.

Practical tips

Convert your .bz2 files to ZIP for sharing, or to 7Z for the tightest possible archiving.

There's no longer any good reason to pick this format for new archives.

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