FAQ
Common Questions
Quick answers about ChessRef data, features, and what to expect in each view.
Is ChessRef free?Yes. All training modes — Opening Drill, the Memory game, Puzzles from real GM games, and Stockfish-powered Analysis — are free, with no daily limits, no signup wall, and no rate limit per IP.
Do I need a Chess.com account to use ChessRef?No. ChessRef reads publicly available game data — you can look up any public Chess.com profile by username without signing in. An account on ChessRef isn't required for any feature.
How is accuracy calculated on ChessRef?Accuracy is computed move-by-move using Stockfish 18, the same engine Chess.com and Lichess use. Each move's evaluation loss is converted into a Lichess-style win-probability delta, then averaged across the game. Higher = closer to engine play; 80%+ at club level is strong, 90%+ at master level is normal.
What does the Opening Drill do?Opening Drill lets you practice the moves of any chess opening from either color. You pick an opening (Sicilian Najdorf, London System, King's Indian — any of the 520 in our catalog), choose white or black, and play the line move by move. The computer plays the book response. Miss a move and we surface the correct move instantly with a retry.
How does the Memory game work?Memorise the Position shows you a real opening tabiya, gives you a few seconds to study it, then clears the board. You reconstruct the position by placing pieces from a tray. The scoring system gives 3 points for correct square, 1 point for adjacent, 0 for missed — so partial recall still counts.
What is the Opening Explorer?The Opening Explorer is a position-keyed database of 4 billion games (Lichess players) and master games (FIDE 2200+). You filter by rating band and time control, then click any move to drill deeper into the tree. Unlike static opening pages, it shows what humans actually play — including weird sidelines that work below 1800.
Where does ChessRef get its data?Player ratings, games, and accuracy come from the public Chess.com API. Opening catalog (ECO codes, move sequences, FEN positions) comes from the Lichess opening dataset. Live position statistics come from the Lichess Cloud Explorer. Engine analysis runs locally in your browser via WebAssembly Stockfish — no server-side eval, no daily limit.
How often is my Chess.com data refreshed?Profile pages cache for 4 hours via ISR. If your most recent games aren't showing up, force-refresh — the next load will pull fresh data from Chess.com.
Why is Magnus Carlsen's rating different on the homepage vs. the leaderboard?The homepage Popular Players cards use a curated snapshot from a previous run; the live leaderboard at /players/grandmasters pulls from the Chess.com API on each visit. The leaderboard is always the more accurate number.
What's the difference between Lichess and Chess.com ratings?Chess.com uses Glicko-1 with conservative deflation; Lichess uses Glicko-2 which inflates faster. A 1500 Chess.com rapid is roughly equivalent to a 1700-1800 Lichess rapid. Use the rating converter at /tools/rating-converter for a precise per-time-control conversion.
How does the eval bar work?The eval bar in analysis and puzzles shows Stockfish's evaluation in centipawns: +1.0 means White is up one pawn worth of position, -2.5 means Black is up two and a half. Mate values clamp to ±100. Above ±2.0 is usually decisive at any rating; below ±0.5 is essentially equal.
Can I run Stockfish analysis without installing anything?Yes — /analysis runs Stockfish 18 directly in your browser via WebAssembly. No installation, no signup, no daily limit. Paste a FEN or PGN and you get engine evaluation as deep as your browser will run.
Can I compare two players head-to-head?Yes. Use /compare/[player1]/[player2] to see rating trends, accuracy by mode, opening overlap, and recent form for any two public Chess.com profiles side by side.
How do I find my opening weak spots?Look up your own profile (chessref.com/your-username) and check the Openings tab. Each opening shows your win rate, accuracy, and most common deviation. Openings with low accuracy and high game volume are the highest-ROI study targets.
Is there a ChessRef mobile app?Not yet — but every page is fully responsive and works in mobile browsers. Drill mode, Memory game, Puzzles, and Analysis all support touch input.