CQL: The Chess Query Language (version 6.0.5)

What is CQL?

Chess Query Language (CQL) searches for user-defined patterns in chess games and studies.

To use CQL

  • first, define the pattern you are looking for in the CQL language;
  • second, run cql specifying that pattern.
CQL will output a new file that contains all the games in the input file that match your pattern.

Quick intro: mirror mates

Suppose the pattern you are looking for is mirror mates, where the mated king is surrounded by empty squares:
Arestov 2013, after 10. h8=N#
(found from CQL file: mirrormate.cql)

You can find these by running

cql -i sample.pgn examples/mirrormate.cql

Here, sample.pgn is the file of games to search. The pattern specifying mirror mate is in the file mirrormate.cql.

The meaning of the terms in the pattern specified in mirrormate.cql are:

Click on the examples tab in the sidebar for more examples.

Additional documentation

Additional contributed documentation (currently in draft form) is available at documentation . The EG discusses CQL in a number of columns, particularly by Emil Vlasàk.


CQL may be downloaded here. Questions or comments about CQL should be directed to costeff at the domain gmail.com .


The current version of CQL is CQL 6.0.5.


CQL was developed by Gady Costeff and Lewis Stiller. It is copyright (c) 2003-2020 and is free. It uses SCID code by Shane Hudson to parse the PGN files. Robert Gamble contributed extensive testing as well as development assistance.