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Archive format

BZ2 converter

A .bz2 file contains data squeezed by bzip2, which compresses harder than gzip at the price of markedly slower operation. Like gzip it handles only one stream at a time, so multi-file archives circulate as .tar.bz2.

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Convert supported files

Runs on your device

Drop BZ2 files here

Batch files can each use a different output. Nothing uploads for local conversions.

Working inputs include camera RAW, browser-local audio/video, PDF, CBZ/CBR comics, office documents, ebooks, markup, 3D models, structured text, images, and archives.

Where BZ2 comes from

Julian Seward released bzip2 in 1996, building it on the Burrows-Wheeler transform that DEC researchers had published just two years earlier. It reigned as the standard better-than-gzip choice for about a decade until xz, and later zstd, largely displaced it.

How BZ2 works

  • Its pipeline runs a Burrows-Wheeler transform, move-to-front coding, run-length encoding, and Huffman coding — no LZ77 matching at all.
  • Operates on independent blocks of 100-900 KB (the digit in bzip2 -9), enabling parallel implementations like pbzip2 and confining corruption to single blocks.
  • Output is typically 10-15% smaller than gzip on text, at several times the CPU cost.
  • Unusually, decompression is nearly as slow as compression.

When to use BZ2

  • Opening older source tarballs published as .tar.bz2.
  • Large text corpora — Wikipedia database dumps still ship as .bz2.
  • Pipelines that exploit block-parallel compressors on many-core machines.

Strengths and limitations

Strengths

  • Meaningfully better ratios than gzip.
  • Block independence aids both parallelism and damage isolation.
  • Free, patent-unencumbered, and installed on virtually every Unix system.

Limitations

  • Slow in both directions — xz beats its ratio while zstd demolishes its speed.
  • Single-stream design with no bundling ability.
  • Effectively a legacy choice; new projects almost never pick it.

Compatibility

The bzip2 utility ships with essentially every Linux and macOS installation, and 7-Zip or libarchive covers Windows. Unlike gzip, browsers do not decompress it automatically for web traffic, so it appears almost exclusively as downloadable files.

Convert BZ2 to another format