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Reversi for two: a board that knows the rules

A reversi board for two people. Sit at one screen, pass a phone back and forth, or send a link after each move to someone far away. The page knows the rules: it shows where a disc can go, will not place a disc the rules do not allow, turns over every disc that has to turn, hands the turn back when a player has no move, and counts the discs at the end. There is no computer opponent, no clock, no account and no ads. Two people, and a game.

Private by design. The game is kept in one place only: the address of this page, after the # sign. Browsers do not send that part of an address to a website, so your moves never reach us. Nothing is saved on this device and nothing is sent. Whoever has the link can see the game and move in it, so send it only to the person you are playing. This page runs no analytics or tracking. How we handle privacy.

The rules, in plain words

The board and the discs

The game is played on all 64 squares of an eight-by-eight board.
The pieces are discs, dark on one side and light on the other. One player is Dark and the other is Light.
The game starts with four discs on the four middle squares, two of each colour, with the same colour on each diagonal.
Dark moves first. Then the players take turns, one disc a turn.

Placing a disc

A move is one disc of your colour, put on an empty square.
It has to close in a row. The new disc has to stand so that, in a straight line from it (across, up and down, or on a diagonal), there are one or more of the other player’s discs in an unbroken row, and then one of your own discs at the far end.
The row turns over. Every disc in that row is turned to your colour. If the new disc closes in rows in more than one direction, all of those rows turn over, in the same move.
A disc that would turn over nothing may not be placed. The page marks the squares where the player to move can go.
A row is closed only by the disc just placed. Discs that end up between two of the other colour because of a turn-over stay as they are.
Once placed, a disc never moves and never leaves the board. It can be turned over many times.

When a player has no move

A player who cannot place a disc anywhere misses that turn, and the other player moves again. The page does this by itself and says so.
A player who can place a disc has to place one. There is no skipping a turn by choice.

How a game ends

The game is over when neither player can place a disc. Most often that is when the board is full, but it can happen sooner.
A win: the player with more discs of their colour on the board wins.
A tie: if both have the same number, nobody wins.
The page shows the plain count of discs. Wikipedia’s article says that in tournaments, when a game ends with squares still empty, those squares are counted for the winner. The page does not add them.
A player may also give up. The page has no button for that: say it out loud and press “New game”.

Playing with someone far away

Make your move, then press “Copy a link to this game” and send the link by text, email or any messenger.
The other person opens the link, sees the board as you left it, makes a move, and sends their link back.
It is not live: a move does not show up on the other screen by itself. The newest link is the game.
The page cannot know who made a move. Anyone holding a link can move for either side, or take a move back.
Who plays Dark? Pick for us can toss a coin.

How the rules were checked

People who write programs for board games test their rules by counting: from the first position, how many different games are possible one turn deep, two turns deep, and so on? The counts are published, and a program with a rule wrong gets a different number.
Each time this page is built, a program counts the games this page would allow from one turn deep to nine turns deep (3,005,288 games at nine), and the build stops unless every count equals the published one.
The counts are from Perft for Reversi on Aart Bik’s website, fetched on October 13, 2026.
That page says turns with no move begin to appear nine turns deep, and games that end early begin eleven turns deep. So on October 13, 2026 the count was also run once, by hand, to twelve turns deep: 1,939,886,636 games, the published number. Of those, 584 were games that had ended early because neither side could move, which is also the published number.
The same program checks a set of small positions we made ourselves: a row of three turned over, rows in all eight directions at once, a row that runs to the edge and is not closed, a turn with no move, and a game that ends with the board not full.
The rules explained on this page are our own wording. They were compared with the rules section of Wikipedia’s article Reversi, read on October 13, 2026. They were not checked by a tournament referee, and Scarlet Beast has no tie to either website.

What this page can’t do

It does not play. There is no computer opponent and no AI in it, and it never suggests a move. The marks show where a disc is allowed to go, not whether going there is wise.
It does not keep your game. The game lives in the address of the page. If the page is closed and the link is lost, the game is gone, and we cannot give it back, because we never had it.
It has no clock, no rating and no list of players.
It knows one set of rules. Wikipedia’s article says an older way to play began with an empty board. This page always begins with the four discs in the middle.
About the name. Wikipedia’s article says the rules used here are the ones the game is sold with under the name Othello, which it says is a registered trademark. That name is not ours, this page is not that product, and Scarlet Beast has no tie to its owner.
It is not an official rulebook. For a tournament, the organizer’s rules decide.
It was tried by a program in one browser, with a mouse and a keyboard. It has not been tried on a touch screen or with a screen reader.

Pages that go with this

Checkers for two and Chess for two: the same kind of board, for those games.
Four in a row for two: the same kind of board, for four in a row.
Games and puzzles: these four boards and eight more pages for play (sudoku, mazes, bingo cards, crosswords and more) on one list.
Pick for us: a coin, dice, or a name out of a hat, to decide who plays Dark.
Visual timer: if you want a time limit for a move.
Sudoku: a puzzle for one.
All the free tools, and how to save them on your phone.

A game, and nothing more. A game can be good company in a long hour, and it cannot do more than that. If things are heavier than a game can hold, Get help now lists people to call. If you are thinking about ending your life, call or text 988 (in the U.S.). If anyone is in danger, call 911.

The tool and the wording on this page were written with AI (Claude) for Scarlet Beast (our AI policy). There is no AI inside this tool: it knows the rules and nothing else, and it never picks a move. It has been checked by a program, with a mouse and a keyboard in one browser; no person has read it through or played a game on it yet, and the Spanish of the page has not been read by a native speaker. It keeps nothing, so it has no line on My data on this device. Also in Spanish: Reversi para dos. Found a mistake? Email [email protected].