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Brotli is an open source data compression library developed by Jyrki Alakuijala and Zoltán Szabadka. Brotli is based on a modern variant of the LZ77 algorithm, Huffman coding and 2nd order context modeling.
Brotli was first released in 2015 for off-line compression of web fonts. The version of Brotli released in September 2015 by the Google software engineers contained enhancements in generic lossless data compression, with particular emphasis on use for HTTP compression. The encoder was partly rewritten, with the result that the compression ratio improved, both the encoder and the decoder have been sped up, the streaming API was improved, more compression quality levels have been added. Additionally, the new release shows performance improvements across platforms, with decoding memory reduction.
Unlike most general purpose compression algorithms, Brotli uses a pre-defined 120 kilobyte dictionary. The dictionary contains over 13000 common words, phrases and other substrings derived from a large corpus of text and HTML documents. Using a pre-defined dictionary has been shown to increase compression where a file mostly contains commonly-used words.
Streams compressed with Brotli have the content encoding type "br".
- Google Chrome has supported Brotli since version 49.
- Microsoft Edge supports Brotli since version 15.
- Mozilla Firefox implemented Brotli in version 44.
- Opera supports Brotli since version 36.
- Safari, no public commitment as of October 2016.
- Apache HTTP Server, in final stages of development.
- Microsoft IIS, no official support nor commitment to implement. There exists a community module that adds support.
- nginx, no official support nor commitment to implement. A ngx_brotli module is provided by Google Inc..
- Node.js, no official support but there exists a community module [shrink-ray https://www.npmjs.com/package/shrink-ray] that adds support.
- "Brotli Compressed Data Format". IETF Internet Drafts. 2014-05-16. Retrieved 2016-11-01.
- "Brotli Source Code - GitHub". github.com.
- Slater-Robbins, Max (20 Jan 2016). "Chrome and Firefox are about to get a lot faster thanks to Google's new data compression algorithm". techspot.com. Retrieved 20 Jan 2016.
- "Introducing Brotli compression in Microsoft Edge". caniuse.com.
- Google Open Source Blog: Introducing Brotli: a new compression algorithm for the internet
- "Smaller Fonts with WOFF 2.0 and unicode-range". Google Developers Blog. 18 Feb 2015. Retrieved 20 Jan 2016.
- Richard Chirgwin (23 September 2015). "Google's new squeeze: Brotli compression open-sourced". The Register.
- Alakuijala, Jyrki; Kliuchnikov, Evgenii; Szabadka, Zoltan; Vandevenne, Lode (2015-09-22). "Comparison of Brotli, Deflate, Zopfli, LZMA, LZHAM and Bzip2 Compression Algorithms" (PDF). Google. Retrieved 25 October 2015.
- Larkin, Henry (2007). Word Indexing for Mobile Device Data Representations. IEEE.
- "Firefox 44 release notes". mozilla.org. Retrieved 2016-01-26.
- Aleksandersen, Daniel. "New Brotli compression filter module now in Apache Web Server". Slight Future. Retrieved 2016-10-06.
- "IIS Brotli extension page". Microsoft IIS Community. Retrieved 2016-10-06.
- "ngx_brotli project page". GitHub. Retrieved 2016-10-06.