This package provides various compression algorithms.

• zstandard compression and decompression in pure Go.
• S2 is a high performance replacement for Snappy.
• Optimized deflate packages which can be used as a dropin replacement for gzip, zip and zlib.
• snappy is a drop-in replacement for github.com/golang/snappy offering better compression and concurrent streams.
• lzw is a drop-in replacement for compress/lzw with 1.4-4x faster decompression and 1.1-2.7x faster compression, depending on the data.
• huff0 and FSE implementations for raw entropy encoding.
• Xpress decompression of the Microsoft XPRESS (MS-XCA) plain LZ77 and LZ77+Huffman formats (the LZ77+Huffman variant is the one used in WIM images and Windows Compact OS / WOF data).
• gzhttp Provides client and server wrappers for handling gzipped/zstd HTTP requests efficiently.
• pgzip is a separate package that provides a very fast parallel gzip implementation.

Use go get github.com/klauspost/compress@latest to add it to your project.

This package will support the current Go version and 2 versions back.

• Use the nounsafe tag to disable all use of the "unsafe" package.
• Use the noasm tag to disable all assembly across packages.

Use the links above for more information on each.

• Sep 25th, 2026 1.20.1

  • zstd: Apply reset options to reused frame decoders by @pellared in #1226
  • flate: Report unexpected EOF for truncated Huffman extra bits by @rupayon123 in #1229
  • flate: Avoid FMA in EstimatedBits for portable rounding by @malt3 in #1224
  • gzhttp: Preserve caller request headers in Transport by @jakezwang in #1225
  • gzhttp: Only decompress a request when gzip is the outermost coding by @youdie006 in #1223
  • zstd/huff0: Optimizations by @lizthegrey in #1203 #1205 #1207 #1204 #1208 #1211 #1209 #1210
  • flate: Speed improvements by @alex in #1220 #1218 #1216 #1215 #1214 #1217

• Sep 2nd, 2026 1.20.0

  • lzw: Add lzw reader/writer in #1189
  • xpress: Add Microsoft XPRESS (MS-XCA) decompression by @MP-GOWTHAM in #1195