See Exactly Where
Your Game Turned.
Import any game from Chess.com or Lichess — or paste a PGN — and prochess.online classifies every move using Stockfish 18.
Import games from any platform
What You Get With a Review
Move Classification
Every move rated — Brilliant through Blunder — by Stockfish 18.
Sandbox Mode
Play alternate moves and see live engine continuations.
Opening Recognition
Identifies your opening from thousands of ECO-coded lines.
Accuracy Scoring
Per-player accuracy — track improvement over time.
Eval Bar
Live evaluation bar updates with every move — see when the balance shifted.
Best-Move Arrows
See exactly where the engine wanted you to go and why.
Move Sounds
Satisfying audio feedback — move, capture, check, and brilliant cues.
Mobile Friendly
Full tap-to-move support. Review games on the go, no app download needed.
Your Games Stay on Your Device
Analysis runs 100% locally via Stockfish 18 (WebAssembly). No account, no upload — ever.
How to Review a Game in 3 Steps
Load Your Game
Enter your Chess.com or Lichess username — or paste any PGN. Games load instantly with opening detection.
Run Analysis
Choose engine depth — Blitz (0.8s), Balanced (1.5s), or Deep (3s). Stockfish 18 analyzes every position locally on your device.
Explore & Learn
Step through each move. See classifications (Brilliant, Blunder…), top engine lines, eval bar, and accuracy scores. Use sandbox mode to try alternatives.
Frequently Asked Questions
Is prochess.online really free?
Yes — completely free. No sign-up, no credit card, no limits. Analysis runs in your browser so there is zero server cost per review.
How accurate is the analysis?
Prochess uses Stockfish 18, one of the strongest chess engines in the world, running natively in your browser via WebAssembly. At 1.5s/move it reaches ~22 ply depth — strong enough for most club players.
Do my games get uploaded anywhere?
Never. The entire analysis pipeline — PGN parsing, Stockfish engine, move classification, and rendering — runs 100% locally inside your browser. Not a single byte of your game data leaves your device.
What is Sandbox Mode?
Drag any piece to explore "what if" variations. The engine evaluates your alternative move live — see the resulting evaluation, best continuations, and whether your idea would have worked.
How long does analysis take?
Blitz mode (0.8 s/move) finishes a 40-move game in under a minute. Balanced (1.5 s) takes about 2 minutes. Deep (3 s) is thorough for correspondence-style review. All modes run on your CPU — a faster device means faster analysis.
Can I use it on my phone?
Yes. The board supports full tap-to-move on iOS and Android. The layout adjusts for smaller screens so the eval bar, move list, and engine lines remain readable. A modern smartphone runs Stockfish 18 fast enough for comfortable review.
What move classifications are there?
Ten categories, matching Chess.com conventions: Brilliant (!!) · Great (!) · Best (★) · Excellent (✓) · Good (•) · Book (📖) · Miss · Inaccuracy (?!) · Mistake (?) · Blunder (??). Each uses win-percentage loss thresholds so the ratings are consistent across all positions.
Does it work offline?
Once the page has loaded, analysis runs entirely offline. Stockfish 18 is cached in your browser — so even with no internet connection you can review games you have already pasted or loaded. Username lookups (Chess.com / Lichess) do require a connection.
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