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Credits & sources

Prologue Chess relies on verified chess sources. No opening line is made up: every variation comes from public references and is checked by a chess engine.

Opening theory

Names, variations and main lines draw on the standard chess literature and public opening encyclopedias (including Wikipedia and the Encyclopaedia of Chess Openings / ECO).

Opening popularity

Each opening's popularity tag is computed from the public games database of Lichess (more than 8 million games analyzed), under an open license.

Validation

Every line is run through a chess engine to rule out any dubious variation. The goal: that you learn real theory, not an approximation.

Chess pieces

The piece set shown in the app and on this site was created by RhosGFX, released under the CC0 license (public domain). Thanks to its author.

Player portraits

The photographs illustrating the player profiles all come from Wikimedia Commons under a free licence. The author and licence appear under each photo, with a link to the original file:

  • François-André Philidor — Augustin de Saint-Aubin, public domain
  • Paul Morphy — unknown author, public domain
  • Wilhelm Steinitz — unknown author, public domain
  • Emanuel Lasker — Agence Rol / BnF, public domain
  • José Raúl Capablanca — anonymous, public domain
  • Alexander Alekhine — Agence Rol / BnF, public domain
  • Mikhail Botvinnik — Jack de Nijs / Anefo, CC0
  • Mikhail Tal — Rob Mieremet / Anefo, CC0
  • Tigran Petrosian — W. Punt / Anefo, CC0
  • Boris Spassky — Rob Bogaerts / Anefo, CC0
  • Anatoly Karpov — Koen Suyk / Anefo, CC0
  • Bobby Fischer — Anefo / Nationaal Archief, CC0
  • Garry Kasparov — Lukasz Kobus (European Union), CC BY 4.0
  • Judit Polgár — Przemysław Jahr / Wikimedia Commons, CC BY-SA 3.0
  • Viswanathan Anand — Gab.pr, public domain
  • Vladimir Kramnik — Georgios Souleidis, CC BY 2.0
  • Magnus Carlsen — Miroslav.vajdic, CC BY 4.0
  • Gukesh Dommaraju — Frans Peeters, CC BY-SA 2.0
  • Hikaru Nakamura — ChessKelly, CC BY 4.0
  • Hou Yifan — Andreas Kontokanis, CC BY-SA 2.0

Publisher

Prologue Chess is published by AGENCE DEBORD EURL. Contact: adebord@agencedebord.com.