Understanding end of game

Hello, I have just started playing Go and am having difficulty understanding when one player has to pass.
Indeed, knowing that putting a stone will reduce the territory of -1, even if one part of the Ban seems to belong to the blacks, for instance, I don’t understand why whites should not insist and keep going in this part of the ban to reduce the number of black territories?

I hope my question is clear and makes sense.
Thanks for your help!


That’s a great question. For new players, ending a game is one of the most difficult to understand aspects of the game.

Note that to answer your question, the concept of of life and death matters [Life and Death at Sensei's Library].

I’ll take a recent game of yours as an example: michael-c137 vs. eliotschlang

For experienced players, it’s clear that the game was basically finished (ready for scoring) after move 28, in this position:

The reason is that experienced players can tell that those white stones at C1, C4 and H8 are dead, which means white cannot prevent that black captures them eventually (assuming black doesn’t blunder).
Also, the border of white’s land (in the lower right) is fully closed and so is the border of black’s land (the rest of the board).
Just by eyeballing it, I can tell that black’s land is bigger than white’s, so black has won the game.

When I use the “estimate score” tool in that position, it confirms my estimation that black has more than white. The computer says black is leading by 19.5 points.

[Warning, the in-game score estimator can be wrong, so you always need to check it with your own evaluation]

You and your opponent continued to put stones on the board for almost 100 more moves. You are both beginners, so it’s understandable that neither of you was aware that all those moves basically didn’t change the situation (although some of those moves were necessary to ensure.that the life & death situation stayed the same).

This can also be seen in the AI review graph:


From move 28 until move 109 (when both of you passed and the game ended), the evaluation graph basically stays the same: black is winning by 19.5 points.

This was the position that was scored after move 109.

Note that the score situation is still the same as it was after move 28: white has land in the lower right, black has the rest of the board, and the score difference is 19.5 points in black’s favour.


In addition to gennan’s great answer, it’s relevant that if you’re using territory scoring, an invading stone does reduce your territory by 1 if you respond to it, since your response takes up a space, but it does not prevent the underlying point from counting, and it will be a point for you at the end of the game, so answering is a net 0 gain/loss

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The short answer is (if) you oblige the opponent to add a stone, at the same time you gave a prisoner so the score stay same.

The longer answer is to consider area rules equivalent to territories rules considering the scoring: you will count the full area you control (including boundaries) and the bigger wins. In that case what happen inside this area (adding stones, removing prisoners) doesn’t matter.

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