Help
How to play chess here, how strong the computer is, what to do if something does not work, and how this site is looked after. No technical knowledge needed.
How to play
- Choose who you are playing under Opponent: Computer (the game starts in this mode; later visits remember your last choice) or Two players sharing one screen. Against the computer, choose whether you play White (you move first) or Black, and a Strength from 1 to 10. The default is 6.
- Click (or tap) one of your pieces. Dots show every square it can legally move to, and rings show pieces it can capture. Click the square you want. Click another of your pieces to change your mind.
- When a pawn reaches the far side you are asked which piece it becomes.
- Prefer typing? Put a move in the Type a move box, for example
e4,Nf3,Bxc6,O-O(castle king side),O-O-Oore8=Q, and press Play. - The game ends in checkmate, a draw (stalemate, too few pieces to mate, the same position three times, or fifty moves with no capture or pawn move: see the rules), or when someone resigns.
- Undo takes back your last move (against the computer, its reply too). Flip board turns the board round. Resign gives up the game. New game starts again with the settings you have chosen. The score for this visit is kept until you close or reload the page.
- Under Moves you can step back through the game with the four buttons, or press any move, to see an earlier position. The board is then read-only: press the last button to return to the game. The name of the opening is shown once a named line is reached, and stays until a new one is.
- Under Game record (PGN) you can copy the game to paste into a chess program or website for analysis.
You can also play with the keyboard. The board is a single stop in the Tab order: press Tab once to reach it, then use the arrow keys to move between squares. Press Enter or Space to pick up a piece and again on the square you want to put it on. Escape drops a piece you have picked up. Press Tab again to leave the board for the buttons. The typed-move box is the quickest way to play without a mouse, and works well with screen readers: every square is read out as, for example, “e4, white pawn, legal move”, and every move is announced.
The rules in short
- White moves first, then the players alternate. Pieces capture by moving onto an enemy piece.
- A king that is attacked is in check and the move must end the check; you may never leave your own king attacked. If you are in check and cannot, it is checkmate and you lose.
- Castling, en passant and promotion work as in the standard rules. Castling is not allowed out of, through or into check, or after the king or that rook has moved.
- A player who is not in check but has no legal move has stalemated: a draw. So is a position where neither side has enough pieces to checkmate, the same position occurring three times, and fifty moves with no capture or pawn move. These draws are declared automatically.
The full rules as this game applies them are in the project’s docs/RULES.md.
How strong is the computer?
The computer was written for this site (it is not a copy of any other chess program) and thinks on your own device, in the background, so the page never freezes. At level 10 it examines millions of possible continuations for every move it makes. Lower levels think for less time, look fewer moves ahead, and have a deliberately blurred sense of which positions are good, so they make the kind of mistakes a human would. They get steadily stronger from 1 to 10.
| Level | What it is like to play | Thinks about |
|---|---|---|
| 1 | Just learning: moves are close to random, though it will often take a piece you leave hanging. | instant |
| 2 | Beginner: sees one move ahead, often blunders. | instant |
| 3 | Casual player: spots simple threats, misses most plans. | instant |
| 4 | Improving player: plays sensibly but drops pieces to two-move tactics. | under a second |
| 5 | Social player: solid, but misses deeper tactics. | under a second |
| 6 | Keen player: rarely drops a piece in one move. | under a second |
| 7 | Club player: sees short tactics and punishes mistakes. | up to one second |
| 8 | Strong club player: a tough opponent. | up to two seconds |
| 9 | Expert: thinks for a few seconds a move. | up to four seconds |
| 10 | Full strength: the best the computer can play. No deliberate mistakes. | up to six seconds |
The levels are approximate and are not an official rating. If you are around 1800, level 7 or 8 should give an even game and 9 or 10 will test you hard. They were checked by playing each level against Stockfish, the strongest free chess engine, held back to chosen ratings; the results are in the project notes (docs/STRENGTH.md).
If something does not work
- Nothing happens when I click. Reload the page (hold Shift while you press reload). The game needs JavaScript switched on. If it still does not respond, tell us which browser you use and we will look into it.
- It says “The computer has a problem”. Reload the page. The computer runs in a background worker, which very old browsers and some privacy tools block; Two players mode does not need it.
- The computer is slow to move. Higher levels deliberately think for a few seconds. Choose a lower level, or press Undo, which cancels its thinking and also takes back your last move.
- I cannot beat the computer. Choose a lower strength; you can change it in the middle of a game.
- I want to go back further than Undo. Press Undo more than once, or start a new game.
How the site is looked after
This is a MediaWright site. The game runs entirely in your browser: it stores nothing about you except your choice of opponent, side and strength on your own device, uses no cookies and has no adverts or trackers. The only outside service it uses is Google Fonts for the lettering.
Every change to the site is tested before it goes live, and each one is recorded, with its build number, on the site updates page. If you find a security problem, please follow the security policy.
Credits
The chess rules, the computer player, the pieces and the page were written for this site. The one thing used from elsewhere is the list of named openings behind the opening book and the opening names: the Lichess chess-openings data set, released into the public domain (CC0). The computer was measured against Stockfish, but no Stockfish code is part of this site. The technical details are in the project README.