Online Chess Engine
Stockfish, in the page, with nothing to install.
Online Engine explained, plus the FAQ
Running the engine
- Set the position on the board, or paste a FEN. A lichess link or a PGN works too.
- Confirm the side to move, then start the search.
- Raise the depth when a position is sharp and the first answer looks unstable.
There is no account, no sign in, and no limit on how many positions you can check. Nothing on this page is gated.
Online, but running on your machine
Most sites that call themselves an online engine send your position to a server and send the answer back. This one does not. The engine is downloaded once, about 7 MB, and every search after that happens in your browser. Two things follow from that. Your positions stay on your device, which matters if you are analysing a game that is still in progress. And there is no shared queue, so the engine is exactly as fast as your own machine whether you are the only visitor or one of thousands.
The engine is Stockfish 17.1, the same open source engine that powers analysis on Lichess and inside Chess DNA. It runs as WebAssembly in your own browser, so your position is never uploaded anywhere. The first search downloads roughly 7 MB of engine; after that it is cached and every later search starts instantly.
Reading an engine evaluation
Evaluations are in pawns and always from White's point of view. +1.4 means White stands better by roughly a pawn and a half; -0.6 means Black is slightly better. M3 means mate in three.
The number matters less than the difference between the moves. Three moves within 0.3 of each other means the position is quiet and your choice barely matters. A top move a pawn and a half clear of the rest means there is a concrete tactic on the board, and that is the position worth stopping on.
Choosing a search depth
Depth is how many half moves ahead the engine searches before it commits to an answer. Depth 10 is quick and already stronger than almost every club player. Depth 18, the setting Chess DNA uses when it analyses your imported games, is far more reliable in sharp tactical positions but takes noticeably longer in a browser tab. Start at the balanced setting and raise it when the position is unclear.
Frequently Asked Questions
Is this Stockfish?
Yes. It is Stockfish 17.1 lite, the same open source engine used for analysis on Lichess and inside Chess DNA, compiled to WebAssembly so it runs in the browser rather than on a server.
Is the online engine free?
Yes, and there is no account. Because the engine runs on your device there is no server cost to recover, so there is no limit on how many positions you analyse.
Does my position get uploaded?
No. The engine binary is downloaded to your browser and the search happens locally. Nothing about the position is sent anywhere, which is why it is safe to use on a game that has not finished.
How strong is it compared to the desktop version?
The browser build is the lite version and searches fewer nodes per second than a native binary on the same machine. At the depths used here that difference does not change the move it picks in ordinary positions; in very sharp tactical positions, raising the depth closes most of the gap.
Can it analyse a whole game?
Not from this page, which searches one position at a time. Paste the PGN into the free game review to have every move checked in one pass, with accuracy for both players and the move that decided the result.
