LZFSE

LZFSE, short for Lempel-Ziv Finite State Entropy, is a lossless data compression algorithm created by Apple and released as open source. It pairs a Lempel-Ziv style stage that finds repeated sequences with a finite-state entropy coder, an implementation of asymmetric numeral systems, that writes the remaining symbols compactly. Apple introduced it at its 2015 Worldwide Developer Conference and shipped it with iOS 9 and OS X 10.11. The design aims for compression ratios close to zlib while decompressing two to three times faster and using less energy, which suits phones and laptops where decompression speed and battery life matter as much as size. A simpler companion algorithm called LZVN is used for inputs below a small size threshold. A reference C library under a BSD licence was published later, and the format is used in Apple file system compression, disk images and the Apple Archive format.