Home * Engines * Lozza

a JavaScript open source chess engine and user interface by Colin Jenkins, first introduced in March 2014. To play a game of chess or to analyze a position via FEN online, Lozza requires a modern web browser since it is instantiated as web worker. As UCI engine, Lozza can be used in Windows GUIs like WinBoard or Arena via Edmund Moshammer's jsUCI tool starting with jsuci.exe lozza.js [1] [2]. Other JavaScript based UCI engines, also source-to-source compiled to JavaScript, are able to run under Lozza's web based user interface [3], for instance the Emscripten port of Stockfish 5, Stockfish-js [4].


Lozza represents the board using a 12x12 mailbox array and two lists of white and black pieces. The principal variation search inside the classical iterative deepening framework features a transposition table indexed by Zobrist keys and state of the art selectivity, amongst others null move pruning, late move reductions, and IID. It has implemented the simplified evaluation function by Tomasz Michniewski [5] [6].

See also

Forum Posts


2015 ...

External Links

Chess Engine

Lozza UI



  1. ^ Lozza - a Javascript web based UCI engine - update v1.10 by Colin Jenkins, CCC, October 18, 2014
  2. ^ Using Lozza in a standard chess UI - @op12no2
  3. ^ Stockfish in Lozza UIs by Colin Jenkins, CCC, January 07, 2015
  4. ^ exoticorn/stockfish-js · GitHub
  5. ^ Javascript chess engine using simplified eval by Colin Jenkins, CCC, September 13, 2014
  6. ^ Re: Some pages discussing practical move generation? by Colin Jenkins, CCC, July 18, 2014

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