Most Go groups either live with two eyes or die. But there is a third possibility that surprises almost every beginner: seki, or mutual life. In a seki, two groups of opposite colours are locked together in such a way that whoever plays first loses, so neither side plays, and both groups stay on the board until the end. This article explains how seki works and why it matters.
The basic idea
Imagine a black group and a white group, each without two eyes, pressed against each other. They share some empty points — shared liberties — between them. If Black fills one of these shared liberties, Black reduces its own liberties too, and White can then capture the black group. The same is true for White.
So neither player wants to play in the shared liberties. If neither group can be attacked from outside, the situation stays frozen. Both groups are alive — not because they have two eyes, but because attacking is suicidal.
A simple description
The most common seki has this structure:
- A black group with no eyes, or one eye.
- A white group with no eyes, or one eye.
- Two shared liberties between them, and no other liberties for either group (or outside liberties that cannot be filled safely).
If Black plays in one shared liberty, the black group is left with fewer liberties than the white group, and White captures it. If White plays there, Black captures White. Therefore both pass over those points, and the seki remains.
Seki and capturing races
Seki often arises from a capturing race — a fight where two weak groups each try to capture the other by filling liberties. When the race is balanced and the remaining liberties are shared, the result can be seki instead of one side capturing the other. Understanding liberty counting is essential here; the fighting category of this site covers capturing races in more detail.
Seki with one eye each
A seki can also occur when each group has one eye and there is one shared liberty between them. Neither side can fill the shared liberty without putting its own group in atari. Again, whoever moves first loses, so neither moves.
How seki is counted on this site
This site uses area scoring and counts every stone on the board as it stands. In a seki:
- Both groups' stones count for their owners.
- The shared liberties touch both colours, so they are neutral and count for nobody.
- An eye inside a seki group is surrounded by that group's stones and counts for its owner under area scoring.
Other rule sets treat eyes in seki differently, but on this site the count is simply literal.
How to recognise a seki during a game
Ask these questions when two weak groups meet:
- Does either group have two eyes? If yes, it is not a seki; the group with two eyes lives.
- Are there empty points that both groups need?
- If I play on one of those points, do I put my own group in atari or give my opponent the first capture?
If playing first would be suicidal for both sides, you are looking at a seki. Leave it alone.
Common beginner mistakes with seki
- Filling a shared liberty out of habit, and losing the group.
- Not realising a seki is possible, and giving up a group that could have lived.
- Assuming a seki group is dead at the end of the game and not protecting it.
Using seki as a defence
When one of your groups is trapped and cannot make two eyes, look for a seki. Sometimes the best a group can do is share liberties with an enemy group so that neither can be captured. That is often far better than losing it entirely.
Practise
Seki is rare in beginner games but appears more as you get stronger. In games against the computer on the home page, when two weak groups press against each other, stop and count shared liberties before filling them. When you play people on the online page, sign in on your account so that you can replay any unusual life-and-death situation.
Related: two eyes to live, eye shapes and vital points, how to study life and death.
A way to picture it
Think of seki as two people holding a rope between them, each needing the other's grip to stay standing. If either lets go to grab more, both fall — but the one who let go falls first. Neither lets go, and both stay upright. The shared liberties are the rope. As long as nobody touches them, both groups live until the end of the game.
A closer look at why nobody moves
Picture the simplest seki. A black group and a white group, neither with eyes, share exactly two empty points and have no other liberties. Each group therefore has two liberties — the same two. If Black plays on one of them, the black group is left with one liberty, and so is the white group. But it is now White's turn, and White fills the last shared point, capturing Black. The same happens in reverse if White moves first. So whoever plays in the shared liberties loses their group, and the rational choice for both players is to leave them empty.
Seki in the endgame
Seki usually becomes clear only in the endgame, when the surrounding borders are closed and each side has checked whether any outside liberties can be filled. Before you pass, look at any groups that are locked together. Make sure you understand which points are shared and must not be filled. Filling them by habit in the final moves — which beginners sometimes do when "tidying up" the board — throws away a whole group.
Frequently asked questions
Is a seki group alive?
Yes. Neither group can be captured as long as nobody fills the shared liberties, and nobody should.
Who wins in a seki?
Neither side wins the local fight. Both groups stay on the board, and the shared liberties are neutral.
Can a seki be broken?
Only if something changes outside, for example one group gains an eye or outside liberties become fillable. Otherwise it stays.
Do eyes in seki count as territory here?
With the literal area scoring used on this site, an eye surrounded only by one group's stones counts for that group. Shared liberties count for nobody.
How common is seki?
Uncommon in beginner games, more common in stronger games with complex fights.
