Frequently asked questions

Last updated: September 7, 2026

Is it really free?

Yes. There is no account, no paywall and no trial. The site carries ads through Google AdSense to cover hosting; using the tool costs nothing.

Do you store my games or my analysis?

No. Your browser fetches games directly from the public Chess.com or Lichess API, and all analysis runs on your device. Nothing is uploaded to us and there is no server that holds your data. "Save analysis" writes a JSON file to your own computer; we never receive a copy. See the privacy policy.

Which sites does it support?

Chess.com and Lichess. Choose the platform when you create a report, then enter the username.

Can I analyze another player's games?

Yes. Any public username works — your own, an opponent's, or a titled player's.

How many games can I analyze at once?

Hundreds is normal; there is an "analyze all matching games" option for a full history. The real limit is your CPU and your patience, because everything runs locally. Narrow by time control and date range to keep batches manageable.

Why is the analysis slow?

Because it is a real Stockfish search running on your machine, not a server. More games and higher depth mean longer waits. Keep the tab open and in the foreground; a live time estimate appears while it works. Lowering the depth or the game count speeds it up.

How strong is the engine?

The default is a single-threaded Stockfish 10 build — well above any human level and appropriate for bulk review. You can point the engine-source setting at a stronger NNUE build you host if you want maximum accuracy. Details are on the method page.

Does it work on a phone?

It runs on mobile, but chess-engine analysis is heavy and phones are slower and thermally limited. For large batches a laptop or desktop is much more comfortable.

Can I save a report and come back to it?

Yes, and you don't have to remember to. A finished report is kept in this browser automatically and listed on the reports page, so it is still there next visit. You can also save it as a JSON file you keep yourself — useful for moving it to another machine or backing it up — and load that file back with no recomputation. You can add more games to an existing report, merge several reports of the same account, or filter one down to a subset and have every stat update.

What do the move labels mean?

Brilliant, Great, Best, Excellent, Good, Book, Inaccuracy, Miss, Mistake and Blunder each have a precise definition — see move classifications.

Is my data used for advertising?

The site uses Google AdSense, which may set cookies to serve and measure ads. It runs no other analytics or tracking. You can review or limit ad personalisation at Google Ads Settings. Full detail is in the privacy policy.

Is it open source?

Yes — the code is on GitHub. It uses Stockfish (GPLv3), chess.js (BSD-2-Clause), the Lichess chess-openings dataset (CC0-1.0) and the Cburnett piece set, each under its own licence.

I found a bug, or I have a feature request.

Please get in touch through the contact page or open an issue on GitHub.