X11 is a chained hashing algorithm approach, taking 11 hashing algorithms from the sphlib. Created by Evan Duffield, X11 consists of blake, bmw, groestl, jh, keccak, skein, luffa, cubehash, shavite, simd, and echo. X11 was first used in Darkcoin, also created by Duffield, but has gone on to be used in many other coins.

GPU miners that mine with the X11 algorithm are currently experiencing reduced power usage (up to 50%) and reduced heat generation compared to the scrypt algorithm.