Can I play Go against the computer here?

Yes, on 9x9. Choose Computer as your opponent and pick Black or White; Black plays first. The computer is a beginner. In a background worker it gives each legal move a score from simple rules of thumb (take stones, rescue a group in atari, do not put its own stones in atari), plays out as many random games as fit in about 450 ms, up to 20,000, and picks the move that won most often, with a bonus for those rules of thumb. It answers within 750 ms; if its search cannot finish in time, or the worker cannot start in your browser, it plays a quick legal move instead, a capture first. After you pass, it passes too when it leads on the board as it stands, komi included, or when no move wins even 15 percent of its random games; it also passes when only its own eyes or small areas of 8 points or fewer that it alone surrounds are left. It has no rank and makes no strength claim. 13x13 and 19x19 are for two players on one device, and there is no online play against another person.

How is Go scored on this board?

By area. Each side counts its stones on the board plus the empty points surrounded only by its own stones. An empty region that touches both colours, or no stone at all, counts for no one, and White adds the komi. Captured stones are not added, as in any area count; the record shows them for interest. Groups you mark dead in the review come off before counting, and their points go to whoever surrounds the area. For example, with a Black wall on column D and a White wall on column F of a 9x9 board, each side has 9 stones and 27 points, 36 each, the 9 points of column E count for no one, 36 + 36 + 9 = 81, and with komi 7.5 the result is W+7.5. There is no Japanese territory scoring.

What is komi, and which values can I use?

Komi is the number of points added to White's area to make up for Black moving first. Here it runs from 0 to 20 in whole or half points, and the board starts at 7.5, the value many area-scoring rule sets use; New game keeps the komi you set. A half point means the game cannot end level; with a whole-number komi an equal count shows as Draw. You can change komi until both players accept the count, and it is saved with the game and written into the SGF record.

Why was my move refused, and how does ko work here?

During play a stone is refused for one of three reasons, and the message names it. The point already has a stone. The stone would leave its own group with no liberties while capturing nothing, which is suicide; a stone that captures is never suicide, because the captured stones come off first. Or the stone would recreate a whole-board position seen earlier in the game, which positional superko forbids: this is what stops a ko from being retaken at once, and it also stops longer cycles. A pass is always allowed in play. The rule cards under the board load the capture that is not suicide and the ko retake on real positions, so you can try them.

How do I end a game and mark dead stones?

Two passes in a row start the scoring review. Tap a stone, or press Enter on it, to mark its whole connected group dead, and tap again to bring it back; dead stones come off for the count and their points go to whoever surrounds them. When both players agree, press Both players accept to fix the result. If you disagree about a group, press Resume play: the dead marks clear, the next player moves, and two new passes start a new review. Against the computer the count is yours to review, because the computer does not judge which groups are dead. Between two players Undo takes back the last pass; against the computer it takes back your own last move and anything the computer played after it.

Can I play on a phone or with the keyboard?

Yes. Tab to the board and move between points with the arrow keys, then press Enter or Space to play. On a small screen the points of a 19x19 board are smaller than a finger, so the column and row pickers under the board, with Play and Pass buttons at least 44 pixels tall, reach every point. With Hints on, the line under the board names the group at the picked point and its liberties, stones in atari are ringed, and the points where the side to move captures are marked.

Is my game saved, and can I export it as SGF?

The game, komi, board size, seats and hint setting are saved in this browser after each move and restored when you come back, repetition history included. The .sgf button downloads the main line: board size, komi, every move and pass, and the result once the count is accepted. The Project button keeps what SGF cannot, such as dead marks and resumed reviews. Open file reads either one back: SGF games on 9x9, 13x13 or 19x19 that start from an empty board with Black first and one move each in turn, following the first line of play where a record branches. Records with handicap or setup stones, and files over 1 MB, are refused with a message saying why.

Go Board

Play Go on a 9x9, 13x13 or 19x19 board in your browser: pass one device between two players, or take Black or White against a beginner computer on 9x9. The rules are applied as you play: captured stones come off at once, a stone that would leave its own group with no liberties and capture nothing is refused, and positional superko refuses any stone that repeats an earlier whole-board position, so a ko cannot be retaken at once, while a pass is always allowed in play. After two passes you mark the dead groups together, and the page counts by area, stones plus the empty points each side alone surrounds, with every sum shown so you can check it by hand; if you disagree about a group, resume play. Hints ring stones in atari and mark the points where the side to move captures, a column and row picker reaches every point on a phone, and you can undo, keep the game saved in this browser, and download it as an SGF record or a project file to open again. Your moves are not sent anywhere.

Board

Opponent

Komi for White

Two players take turns on this device. The computer plays 9x9 only. Komi runs from 0 to 20 in whole or half points.

board9x9, two players, komi 7.5

ColumnRow

E5: empty.

Arrow keys move between points; Enter or Space plays a stone there, or in the scoring review marks its group dead or alive. The column and row pickers reach every point with larger buttons.

9x9 board. Black: none. White: none. Black to move.

area scorepreview: every stone counted as alive

Loading the board and any saved game.

Black: 0 stones + 0 points = 0
White: 0 stones + 0 points = 0
komi: 0 + komi 7.5 = 7.5
neutral: 81 points, counted for no one
dead: marked after two passes
total: 0 + 0 + 81 = 81 points
result: W+7.5, preview with every stone alive
record: 0 stones placed, 0 captured

No moves yet.

saved in this browser: board, turn, repetition history and komi

Black area: 0

White area + komi: 0 + 7.5 = 7.5

Neutral: 81 points

Result: W+7.5 preview

Board as text

    A B C D E F G H J
 9  . . . . . . . . .
 8  . . . . . . . . .
 7  . . . . . . . . .
 6  . . . . . . . . .
 5  . . . . . . . . .
 4  . . . . . . . . .
 3  . . . . . . . . .
 2  . . . . . . . . .
 1  . . . . . . . . .

X Black   O White

The rules on real positions

Each one loads on 9x9 as a new game, so you can try the move yourself. Against the computer, you take the side to move.

A lone stone on an empty 9x9Black at the centre E5, White in the corner A1
E5 has 4 liberties, A1 has 2
Black fills the last liberty of a White pairC9 has no empty neighbour of its own
both White stones come off first, so it is a capture, not suicide
White retakes a ko at onceD6 would restore the board of one move ago
refused by positional superko; a pass or a move elsewhere is allowed

Common questions

Can I play Go against the computer here?: Yes, on 9x9. Choose Computer as your opponent and pick Black or White; Black plays first. The computer is a beginner. In a background worker it gives each legal move a score from simple rules of thumb (take stones, rescue a group in atari, do not put its own stones in atari), plays out as many random games as fit in about 450 ms, up to 20,000, and picks the move that won most often, with a bonus for those rules of thumb. It answers within 750 ms; if its search cannot finish in time, or the worker cannot start in your browser, it plays a quick legal move instead, a capture first. After you pass, it passes too when it leads on the board as it stands, komi included, or when no move wins even 15 percent of its random games; it also passes when only its own eyes or small areas of 8 points or fewer that it alone surrounds are left. It has no rank and makes no strength claim. 13x13 and 19x19 are for two players on one device, and there is no online play against another person.
How is Go scored on this board?: By area. Each side counts its stones on the board plus the empty points surrounded only by its own stones. An empty region that touches both colours, or no stone at all, counts for no one, and White adds the komi. Captured stones are not added, as in any area count; the record shows them for interest. Groups you mark dead in the review come off before counting, and their points go to whoever surrounds the area. For example, with a Black wall on column D and a White wall on column F of a 9x9 board, each side has 9 stones and 27 points, 36 each, the 9 points of column E count for no one, 36 + 36 + 9 = 81, and with komi 7.5 the result is W+7.5. There is no Japanese territory scoring.
What is komi, and which values can I use?: Komi is the number of points added to White's area to make up for Black moving first. Here it runs from 0 to 20 in whole or half points, and the board starts at 7.5, the value many area-scoring rule sets use; New game keeps the komi you set. A half point means the game cannot end level; with a whole-number komi an equal count shows as Draw. You can change komi until both players accept the count, and it is saved with the game and written into the SGF record.
Why was my move refused, and how does ko work here?: During play a stone is refused for one of three reasons, and the message names it. The point already has a stone. The stone would leave its own group with no liberties while capturing nothing, which is suicide; a stone that captures is never suicide, because the captured stones come off first. Or the stone would recreate a whole-board position seen earlier in the game, which positional superko forbids: this is what stops a ko from being retaken at once, and it also stops longer cycles. A pass is always allowed in play. The rule cards under the board load the capture that is not suicide and the ko retake on real positions, so you can try them.
How do I end a game and mark dead stones?: Two passes in a row start the scoring review. Tap a stone, or press Enter on it, to mark its whole connected group dead, and tap again to bring it back; dead stones come off for the count and their points go to whoever surrounds them. When both players agree, press Both players accept to fix the result. If you disagree about a group, press Resume play: the dead marks clear, the next player moves, and two new passes start a new review. Against the computer the count is yours to review, because the computer does not judge which groups are dead. Between two players Undo takes back the last pass; against the computer it takes back your own last move and anything the computer played after it.
Can I play on a phone or with the keyboard?: Yes. Tab to the board and move between points with the arrow keys, then press Enter or Space to play. On a small screen the points of a 19x19 board are smaller than a finger, so the column and row pickers under the board, with Play and Pass buttons at least 44 pixels tall, reach every point. With Hints on, the line under the board names the group at the picked point and its liberties, stones in atari are ringed, and the points where the side to move captures are marked.
Is my game saved, and can I export it as SGF?: The game, komi, board size, seats and hint setting are saved in this browser after each move and restored when you come back, repetition history included. The .sgf button downloads the main line: board size, komi, every move and pass, and the result once the count is accepted. The Project button keeps what SGF cannot, such as dead marks and resumed reviews. Open file reads either one back: SGF games on 9x9, 13x13 or 19x19 that start from an empty board with Black first and one move each in turn, following the first line of play where a record branches. Records with handicap or setup stones, and files over 1 MB, are refused with a message saying why.

Scoring is by area: each side counts its stones plus the empty points only its own stones surround, a region touching both colours or neither counts for no one, and White adds the komi you set, 0 to 20 in half points. Suicide is refused and positional superko refuses any stone that would repeat an earlier whole-board position, while a pass is always allowed in play; after two passes the players mark dead groups by hand before the count, or resume play if they disagree, and against the computer that count is yours to review, not an automatic life-and-death judgment. The computer plays 9x9 only, as a beginner that answers within 750 ms with no rank or strength claim, and there is no Japanese territory scoring.