Puzzle data
The tactical collection derives from the public Lichess puzzle database. Raw fields include FEN, move sequence, rating, and themes. ChessGrade adds level-based selection, filters, history, review scheduling, presentation, and educational context. Consult Lichess documentation for the license and attribution that apply to the dataset version.
Stockfish
Stockfish is open-source chess engine software distributed under the GNU GPL. It supports evaluation and line verification. It does not write the articles, and a numerical score is not presented as a complete pedagogical explanation.
AI and providers
Narrative features may use Google Gemini to turn structured data into explanations. Outputs are interpretive and should be checked. Stripe processes subscriptions; AWS may host application components and data; email providers deliver transactional messages.
User-submitted PGN
Games submitted by a user are processed for the requested analysis. Users must have permission to submit that material. Chess.com and Lichess remain independent services and trademarks.
Removal and correction
Send attribution, correction, or removal requests to [email protected] with a URL and explanation. We review source, license, and impact before changing material.
The value ChessGrade adds
Being transparent about where the data comes from is part of our editorial commitment. The raw puzzle database is public, but raw data — a list of FENs, moves, and ratings — teaches nothing on its own. ChessGrade's work lives in the curation layer: classifying positions by theme and phase, calibrating difficulty, grouping recurring mistakes, scheduling reviews, and above all writing the didactic explanation of each pattern. It is this organization and our own explanatory content that distinguish the platform from a simple redistribution of a third-party dataset.