Content in these games that came from somewhere else, and the terms it arrived under.
The word lists are built from the English Speller Database (ESDB, previously known as SCOWL).
Copyright 2000-2026 by Kevin Atkinson
Permission to use, copy, modify, distribute, and sell any part of the English Speller Database (ESDB, previously known as SCOWLv2), or word lists created from it, is hereby granted without fee, provided that the above copyright notice appears in all copies and that both the above copyright notice and this notice appear in supporting documentation. Kevin Atkinson makes no representations about the suitability of this database for any purpose. It is provided "as is" without express or implied warranty.
ESDB carries its own upstream credits, reproduced here in full:
ESDB is derived from many sources, most of which are in the Public Domain. Data from the Corpus of Contemporary American English (COCA) was also used.
All data from COCA comes from 3-gram data that is not freely available; however, the usage is within the rights given by the NDA that was signed when purchasing the data. More information on COCA is available at english-corpora.org/coca.
The primary source of words for ESDB comes from 12dicts and ENABLE2K. Both are in the Public Domain, but Alan Beale <[email protected]> deserves special credit as he is the author of 12dicts and a major contributor to ENABLE2K. In addition, he gave me an incredible amount of feedback and created a number of special lists in order to help improve the overall quality of ESDB.
The Microban levels are the collection by David W. Skinner, released for free distribution with attribution. Source.
Positions come from the Lichess puzzle database, released by Lichess under the Creative Commons CC0 1.0 Universal public domain dedication. Each record keeps the puzzle id, position, rating and themes from that database.
The move evaluations were computed ahead of time with Stockfish (GPL-3.0). Stockfish is not part of this site; the evaluations it produced are plain data.
The chess piece set, board and all other Passant artwork were drawn for this site.
Legal moves, check and move notation come from chess.js, which is included in the game's script.
Copyright (c) 2025, Jeff Hlywa ([email protected])
All rights reserved.Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:
- Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
- Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.