ChessGrader / PGN analyzer
Paste any PGN. Get a full game review.
Any chess game in PGN form — a tournament game you transcribed, an export from another site, a classic from 1972 — pasted into ChessGrader becomes a complete Stockfish review: every move graded, accuracy scored, blunders explained. Free, in your browser, no upload.
Who this is for
- OTB tournament players. Enter your scoresheet as PGN and get the same review online players take for granted — before the next round if you're quick.
- Players on other sites. ChessGrader imports chess.com and Lichess games by username, but any site that exports PGN works here — which is all of them.
- Historic games. Paste Fischer–Spassky and see which moves an engine calls Brilliant. (Fewer than the commentators did.)
- Coaches. Review a student's game in a minute, with grades you can explain because the thresholds are public.
How it works
Paste your PGN on the homepage. ChessGrader parses it and runs Stockfish 17.1 — compiled to WebAssembly — through every position, right there in your browser tab. Each move gets a fixed 100,000-node search; the moments that matter get re-verified at 600,000 nodes with the engine's top two lines. A modern phone takes about a minute per game.
Privacy is structural, not a promise. Your PGN is never uploaded — the analysis has no server side at all. If the game is a tournament preparation secret, it stays one.
What the report shows
Every move graded on a ten-step ladder, plus an accuracy score (Lichess's documented formula — see what counts as good), average centipawn loss, an eval graph, an estimated game rating, and drills built from the mistakes. The grades:
| Grade | What it means |
|---|---|
| Brilliant (!!) | The engine's best move and a genuine sacrifice, still sound afterwards — verified at 600,000 nodes |
| Great (!) | The only good move (second-best line at least 18% worse), or the precise punish of a big swing — verified at depth |
| Best (★) | Matches the engine's top choice, or ties its second line within 10 centipawns |
| Excellent | Loses no more than 25 centipawns |
| Good | A bigger slip, but under a 10% win-probability drop |
| Book | A theory-range move in the first 8 moves |
| Inaccuracy (?!) | At least 10% win probability lost |
| Miss (✗) | Your opponent handed you the game and you gave it straight back — including missed forced mates while winning |
| Mistake (?) | At least 20% lost |
| Blunder (??) | At least 30% lost |
Full formulas — win probability, node budgets, mate handling, the verification pass — are on the methodology page. No black box.
What your PGN needs
- Standard chess. No Chess960, no variants.
- A complete, legal move list. Standard algebraic notation, as every site and most scoresheet apps export it. Headers are optional but nice — player names make the report friendlier.
- At least a few moves. A three-move miniature grades fine; an empty game doesn't.
If your games live on chess.com or Lichess you can skip the copy-paste entirely — ChessGrader imports chess.com games and Lichess games by username.
Frequently asked questions
What is a PGN file?
PGN stands for Portable Game Notation, the universal text format for chess games. It lists the moves in standard algebraic notation, optionally with headers like player names, ratings, and the result. Every major chess site and app can export it.
How do I export a PGN from chess.com?
Open the finished game, look for the share or download option, and choose PGN. Chess.com offers both a downloadable file and copyable PGN text. Though for chess.com games it is faster to type your username into ChessGrader and let it fetch your games automatically.
How do I export a PGN from Lichess?
On any game page, the share and export menu below the board offers the PGN as text or a download. Lichess also lets you export your entire game history at once. As with chess.com, ChessGrader can fetch your Lichess games directly by username instead.
Is there a file size or game limit?
No. ChessGrader is free and unlimited with no daily cap. Analysis time scales with game length — roughly a minute per game on a modern phone, faster on desktop — but there is no limit on how many games you paste.
Does it support Chess960 or other variants?
No. ChessGrader analyzes standard chess only. Chess960, Crazyhouse, Atomic, and other variants are not supported, because the engine evaluation and grading thresholds are built for the standard game.
Is my PGN uploaded anywhere?
No. The Stockfish analysis runs as WebAssembly inside your browser, so the PGN never leaves your device. There is no server-side analysis component at all, and reports are cached only in your own browser storage.
Can I analyze a game that ended in the opening?
Yes, as long as there are at least a few moves to grade. Very short games produce thin reports — expect mostly Book moves and one decisive error — but the analyzer handles them fine.