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Four in a row for two: a board that knows the rules

A four in a row 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: a disc dropped in a column falls to the lowest empty place, a full column takes no more discs, and the page says when a player has four in a row or when the board is full and nobody has. 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 board stands upright. It has seven columns and six rows: 42 places for a disc.
One player has the red discs and the other has the yellow discs. On this page a yellow disc has a dot in the middle, so the two can be told apart without colour.
The game starts with the board empty.
On this page Red always moves first. Then the players take turns, one disc a turn.

Dropping a disc

A move is one disc of your colour, dropped into a column.
The disc falls. It lands on the lowest empty place of that column: on the bottom row, or on top of the disc that is already there. A disc cannot be left hanging with an empty place under it.
A full column takes no more. When a column has six discs, choose another. The page says which columns are still open.
Once dropped, a disc never moves and never leaves the board.
There is no skipping a turn.

How a game ends

A win: the first player to have four of their own discs next to each other in one straight line wins. The line can go across, up and down, or on a diagonal.
The game stops there. The page marks the four discs and takes no more moves.
More than four in one line wins just the same.
A draw: if all 42 places are full and nobody has four in a row, nobody wins.
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 Red? Pick for us can toss a coin.

How the rules were checked

One way to test a program that knows a game is to count: after one disc, after two discs, and so on, how many different boards can there be? For this game 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 different boards this page would allow after every number of discs from none to ten (1,662,623 boards after ten discs), and the build stops unless every count equals the published one.
The counts are sequence A212693 in the On-Line Encyclopedia of Integer Sequences, fetched on October 13, 2026.
What that test can show: nobody can have four in a row before the seventh disc, so from seven discs on the count comes out right only if the page stops a game at four in a row. A four on a diagonal needs at least ten discs on the board. So on October 13, 2026 the count was also run once, by hand, for every number of discs up to fourteen: 75,437,595 different boards after fourteen discs, the published number, and every count before it equal too.
The same program checks a set of small positions we made ourselves: where a disc lands, a full column, four across, four up and four on each diagonal, three that is not four, a row broken by the other colour, five in a row, and a full board with no four.
The rules explained on this page are our own wording. They were compared with Wikipedia’s article on the game, read on October 13, 2026. They were not checked by a 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 would land, not whether dropping it 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 board. Wikipedia’s article says seven columns by six rows is the size used most, and that other sizes and other ways to play exist. This page has the seven-by-six board and the plain game only.
About the name. Wikipedia’s article says the game was first sold under the name Connect Four, which it says is a 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. If you play for something that matters, agree on the rules before you start.
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

Reversi for two, Checkers for two and Chess for two: the same kind of board, for those games.
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 Red.
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: Cuatro en línea para dos. Found a mistake? Email [email protected].