Caissa Codex

Chess Opening Identifier

Find any chess opening by name, by the moves of a game (pasted or played on the board) or by a FEN position, with its ECO code and the lines that follow.

Or identify it from the moves

Drag or tap the pieces to play moves.

Match

Play the moves on the board, or paste them below.

With or without move numbers; a whole PGN works too.
Search by a FEN position instead

Paste any FEN to find every opening that reaches that exact position, whatever the move order, which helps with transpositions.

What opening did I play?

Copy the moves of your game and paste them into the box above. Move numbers are optional, and a whole PGN from Lichess, chess.com or a database works too, headers and clock comments included. Or play the first moves on the board. The identifier names the opening and the deepest named line your game followed, shows its ECO code and the move with which your game left the named lines, and links to the line's page: how it scores in rated Lichess games (for the most-played lines also by rating band and in master games) and what Stockfish makes of the position.

How the identifier works

Every one of the 3,690 named lines in the Lichess chess-openings dataset is indexed by its moves. The identifier finds the longest named line that your moves begin with, so a game that leaves known theory early still gets the name of the opening it started as, along with how many moves past documented theory it went.

Different move orders can reach the same position. Search by FEN to list every named line that arrives at a position, whatever the order of moves; the move counters and the en-passant field are ignored. The name search matches parts of names, with or without accents and apostrophes (najdorf, grunfeld, kings indian), forgives a typo, knows short names such as QGD and KID, and takes ECO codes such as B20.

Examples

https://chesscodex.org/search