What Just One Chess Is
Just One Chess is a browser chess game built around a single idea: you press play, and the site decides the details. Your colour, the time control, the opponent's strength and the opening are all chosen at random, so every game is a fresh problem and nothing has to be configured first. There is no account, no public rating and no matchmaking queue.
The game does not start from the initial position. Each match begins from one of 25 named opening positions, after eight moves by each side, so you spend your time on the middlegame decisions rather than on opening theory. The name of the opening is revealed when the match begins.
Why It Exists
Most chess sites ask for a login, a rating pool and a choice of settings before the first move. We wanted the opposite for casual practice: a short game against a computer opponent that you can start in one click, on a phone or a laptop, and finish in a few minutes. The randomness is deliberate. Playing both colours against opponents of different strengths, from unfamiliar starting positions, is a more varied workout than repeating the same setup.
How the Engine Works
The opponent is a chess engine written in C++ and compiled to WebAssembly, so it runs inside your browser in a background Web Worker. It does not need a server for move calculation, and your moves are not sent anywhere to be analysed. The game rules and legality checks use the open-source chess.js library, and the board is drawn with chessground.
The engine has eleven strength levels, from roughly 1000 to 3000. A level is defined by how much the engine is allowed to search (a node budget), how much of its chess knowledge it is allowed to use at the lower levels, and how often it makes a deliberate inaccuracy. The level labels are practical estimates meant to help you compare opponents, not official ratings from any rating body.
How the Starting Positions Are Chosen
The 25 starting positions cover the main opening families: the Ruy Lopez, Italian, Scotch and Four Knights; four Sicilian systems; the French, Caro-Kann, Scandinavian and Pirc; the Queen's Gambit Declined, Slav and Semi-Slav; the King's Indian, Nimzo-Indian, Grünfeld, Benoni and Dutch; and the English, London, Catalan, Réti and Trompowsky. Each is a recognisable line, not a random scramble of moves.
We run the same engine over every one of these positions and publish what it finds: the evaluation, its preferred continuation and the plans for both sides. See the engine analysis of all 25 arena positions. Most start positions are close to level; a few give one side a small but clear edge, and the page shows which.
How We Write the Guides
The opening and strategy guides are written to explain ideas that apply to the positions you can actually reach in the game: typical plans, pawn structures, common traps and the exact starting positions. Where a guide shows an engine evaluation or a move sequence, it comes from the analysis described above rather than from memory. If you find an error in a guide, please tell us and we will correct it.
Privacy by Design
No password or player profile is created. Game state stays in your browser, and the only thing we store locally is your sound preference. Ordinary requests to the web host, and how advertising may be handled in the future, are described in the Privacy Policy.
Contact & Corrections
Just One Chess is independently operated. To share feedback, report a bug, point out a mistake in a guide, or ask about the project, visit the Contact page or email contact@justonechess.com.