Universal Chess Interface

From Wikipedia, the free encyclopedia

The Universal Chess Interface (UCI) is an open communication protocol that enables chess engines to communicate with user interfaces.[1][2]


In November 2000, the UCI protocol was released. Designed by Rudolf Huber and Stefan Meyer-Kahlen, the author of Shredder, UCI rivals the older "Chess Engine Communication Protocol" introduced with XBoard/WinBoard.

In 2002, Chessbase, the chess software company which markets Fritz, began to support UCI, which had previously been supported by only a few interfaces and engines.

As of 2021, well over 300 engines are known to directly support UCI.


By design, UCI assigns some tasks to the user interface (i.e., presentation layer) which have traditionally been handled by the engine (at the business layer) itself.[citation needed]

Most notably, the opening book is usually expected to be handled by the UI, by simply selecting moves to play until it is out of book, and only then starting up the engine for calculation in the resulting position. UCI does not specify any on-disk format for the opening book. Different UIs usually have their own proprietary formats.[citation needed]

While the UI can also take responsibility for handling endgame tablebases, this is arguably better handled in the engine itself, as having tablebase information can be useful for considering possible future positions.[3]

Stefan-Meyer Kahlen's UCI protocol in Shredder uses a variation of long algebraic notation for moves. A "nullmove" from the Engine to the GUI should be sent as 0000.[4]

  • e2e4
  • e7e5
  • e1g1 (white short castling)
  • e7e8q (for promotion)


The uci_limitstrength parameter tells engines with this feature to play at a lower level. The uci_elo parameter specifies the Elo rating at which the engine will aim to play. Engines that have implemented uci_elo include Delfi, Fritz, Hiarcs, Houdini, Junior, Rybka, Shredder, Sjeng and Stockfish.


The UCI has been modified to play some chess variants. Some of these are:[5]

  • Universal Shogi Interface (USI), a dialect for shogi;[6]
  • Universal Chinese Chess Interface (UCCI), a dialect for xiangqi.[7]

Each of these protocols may also define variants of Portable Game Notation (PGN) and Forsyth–Edwards Notation (FEN). The XBoard CECP is said to require far fewer changes to support variants.[5]

See also[edit]


  1. ^ "Chess engines". Business World Online. 2017-04-06. Retrieved 2018-06-14.
  2. ^ Torres, JC (2014-06-23). "Lichess embraces blind players with new chess site features". SlashGear. Retrieved 2018-06-14.
  3. ^ Chess Life. United States Chess Federation. 2003.
  4. ^ "UCI protocol". www.wbec-ridderkerk.nl. Retrieved 2018-06-14.
  5. ^ a b Evert. "UCI protocol for chess variants". TalkChess.com.
  6. ^ "The Universal Shogi Interface (USI)". hgm.nubati.net.
  7. ^ "中国象棋电脑应用规范(五):中国象棋通用引擎协议". www.xqbase.com.

External links[edit]