Bzip2 is a freely available, patent free, data compressor.

bzip2 compresses files using the Burrows-Wheeler block-sorting text compression algorithm, and Huffman coding. Compression is generally considerably better than that achieved by more conventional LZ77/LZ78-based compressors, and approaches the performance of the PPM family of statistical compressors.

The archive file format of bzip2 (.bz2) is incompatible with that of its predecessor, bzip (.bz).