 When compressing ZIP or gzip files, 7-Zip uses its own DEFLATE encoder, which may achieve higher compression, but at lower speed, than the more common zlib DEFLATE implementation.The 7-Zip deflate encoder implementation is available separately as part of the AdvanceCOMP suite of tools.The decompression engine for RAR archives was developed using freely available source code of the unRAR program, which has a licensing restriction against creation of a RAR compressor.