Chesscorpus credits and licences

Last updated: 29 de agosto de 2026

Chesscorpus is no longer just a games database: it is a chess platform with player search, FIDE profiles, an opening explorer, tactics/strategy/opening/endgame trainers, cloud analysis and user accounts. This page credits the third-party material behind each tool and its licence.

Licences

Different parts of Chesscorpus are released under different licences, depending on source:

• Games collection. It incorporates material under CC BY-SA 4.0 (Lichess Broadcasts) and CC BY 4.0 (Figshare), plus public-domain or unlicensed material (Ajedrez Data AJ-OTB, ICCF correspondence, Chess-Results). The ShareAlike clause of CC BY-SA propagates to the derived work, so the Chesscorpus games corpus is offered under CC BY-SA 4.0 insofar as the sources permit.
• Tactics puzzles. From the Lichess Puzzle Database, released as CC0 (public domain). Included as-is, with no attribution requirement.
• Engine software. The Stockfish chess engine is free software under the GPLv3. It runs in each visitor's browser; its source and licence ship with the application (the /stockfish folder).

Anyone may copy, redistribute and transform the game and puzzle data, even commercially, provided the source is credited and the stated licences are respected. This obligation also covers the database sui generis right (art. 4 of CC BY-SA; Directive 96/9/EC).

These licences cover Chesscorpus's selection, normalisation, indexes and other contributions, and third-party material only to the extent permitted by its source licence. They do not licence rights belonging to an external source, nor do they affect Stockfish, which keeps its GPLv3 licence.

How to cite

Chesscorpus (2026). Chess platform: game database, trainers and analysis. https://chesscorpus.org — data under CC BY-SA 4.0 and CC0.

Game sources

The games collection is drawn from public broadcasts and databases, including Lichess Broadcasts (CC BY-SA 4.0), Ajedrez Data AJ-OTB (public domain), Chess Database on Figshare (CC BY 4.0), ICCF/AJ-CORR correspondence (free use per provider) and 110,000 games from public Chess-Results PGNs (no licence granted; published as factual records, with tournament provenance and URL retained, and comments, variations and clock data removed). For the endgame trainer, the exact result of positions up to seven pieces comes from the Syzygy tablebases by Bojun Guo and Ronald de Man, served via tablebase.lichess.ovh. FIDE ratings come from ratings.fide.com and the fideratings.com mirror; federation flags from flagcdn.com (public domain).

Tactics trainer: the puzzles

The puzzles (normal, timed, storm, streak, depth and candidate-moves modes) come from the Lichess Puzzle Database (CC0). Chesscorpus filters, normalises and serves them with its own spaced-repetition (FSRS) and rating system; the puzzle content itself is public domain.

Chess engine (Stockfish)

Every function that computes moves and evaluations — the tactics trainer (candidate moves), the endgame trainer, cloud analysis and the opening suggestions — uses the Stockfish engine (version 18 lite, WASM build). Stockfish is free software under the GPLv3 and runs entirely on the visitor's device; Chesscorpus does not run the engine on its servers. Cloud analysis may additionally use Stockfish through chess-api.com. The engine's licence and source are included in the /stockfish folder of this application.

Endgame positions and cited books

Book titles and author names are used only to identify and cite the bibliographic source. Chesscorpus does not reproduce the books' explanations, commentary, analysis, or text excerpts; nor does it reproduce their pages, layout, or diagrams as published. Chesscorpus claims no rights in the cited works and does not imply affiliation, sponsorship, authorisation, or endorsement by their authors or publishers.

Each exercise retains one isolated position as FEN and the minimum factual data needed to locate it. The position is treated as a chess fact, separately from the creative expression used to explain it. This does not deny or limit any rights that may subsist in texts, illustrations, cover art, original titles, or the original selection and arrangement of a work or collection. Those rights remain with their respective owners.

This approach follows the distinction between facts and original expression, without prejudice to article 10 of Spain's Intellectual Property Act or the protection for an original selection or arrangement of database contents under Directive 96/9/EC.

A rights holder who believes that a reference or image affects their rights may contact chesscorpus@gmail.com to request that the reference or cover be corrected or removed. The request will be reviewed as a priority.

Third-party marks

Chesscorpus is an independent project, not affiliated with FIDE, Lichess, Chess-Results, Chess.com, chess24, the Stockfish project or chess-api.com. Their names and marks belong to their respective owners and are cited for identification only.

Corrections

For attribution corrections or licensing questions, write to chesscorpus@gmail.com.