Free Chess Game Analysis

How to analyse a game

1. 1

   Paste the PGN into the box, or open a .pgn file. The example game loads with one tap if you just want to see how it works.

2. 2

   Press Start analysis. The engine is about seven megabytes and is fetched once, so the first run takes a moment.

3. 3

   Press Review the whole game. Progress runs along the move list as each position is searched.

4. 4

   Tap any move to see its verdict, the engine’s preferred move, and the lines from that position.

Frequently asked questions

Is the analysis really free, with no account?

Yes. The engine runs in your browser, so there is nothing to meter. No sign-up, no credits, no daily cap on how many games you review.

Which engine is this, and how strong is the analysis?

Stockfish 18, the lite single-threaded WebAssembly build. The whole-game review searches each position to a fixed shallow depth so a long game finishes in reasonable time; stepping to a single position searches it deeper. For serious opening preparation a desktop engine given minutes per move will always see further.

Does my game get uploaded?

No. The PGN is parsed in the page and the engine searches on your own processor. Nothing about the game leaves your device.

What do the accuracy numbers mean?

Each move is scored by how much winning chance it gave away compared with the engine’s choice, and the accuracy figure is the average across a side’s moves. It is a summary, not a rating: a quiet game with few decisions will score higher than a sharp one played just as well.

Why is the first analysis slow?

The WebAssembly engine has to be downloaded before it can search. After that it is cached, and later visits start immediately.

How do I analyse a game I played on paper?

Photograph the scoresheet and run it through the ScanChess scanner first. It reads the handwriting, checks every move against the rules and gives you a PGN you can paste straight in here.