"Two eyes live" is the golden rule of life and death. But beginners often count two eyes, relax, and then watch their group die. The usual culprit is a false eye: an empty point that looks like an eye but cannot do an eye's job. This article explains what false eyes are, how to spot them with a simple test, and how to use them against your opponent.
What makes an eye real
An eye is only real if the opponent can never play inside it while your group still has other liberties. That requires all the stones around the eye to be firmly part of your group. If one of those surrounding stones can be cut off and captured, the opponent can play inside the "eye" as a capture — and the eye disappears.
A false eye on the edge
Look at the stone on d1. It touches c1 (empty), d2 (white) and e1 (white). It is not connected to the other black stones, and its only liberty is c1. So a white stone at c1 is not suicide: it captures d1 and then has a liberty where d1 was. The point c1 cannot serve as an eye.
The diagonal test
A quick way to judge an eye is to look at its diagonal points:
- For an eye in the middle of the board (four diagonals), you need to control at least three of the four diagonals. If the opponent holds two, the eye is usually false.
- For an eye on the edge (two diagonals), you need both diagonals. If the opponent holds one, the eye is usually false.
- For an eye in the corner (one diagonal), you need that one diagonal.
In the diagram above, the edge eye at c1 has diagonals b2 and d2. White holds d2, so by the test the eye is false — exactly what the capture of d1 shows.
The test is a rule of thumb, not a law; the real question is always whether a surrounding stone can be captured. But it works in the great majority of positions and takes only a second.
Why false eyes appear
False eyes usually form when:
- Your group's shape has a diagonal weakness that the opponent occupied.
- Stones around the eye are not connected to the main group.
- You tried to save moves by leaving a gap, and the opponent played into it.
How to fix a false eye
If you see that an eye is false but it is not too late:
- Connect the stone that can be cut off, so that capturing it is no longer possible.
- Take the key diagonal point yourself before the opponent does.
- Make another eye elsewhere, if the false one cannot be repaired.
How to use false eyes against your opponent
When attacking a group, look at its eye points' diagonals. Playing on a key diagonal can turn a real eye into a false one — often the decisive move in a life-and-death fight. Many classic killing techniques are simply "make one of the eyes false".
Counting eyes honestly
When you check your groups during a game, count only real eyes. A group with one real eye and one false eye has one eye, and it can be killed. This is the most common way beginners overestimate a group's safety.
Practise
In games against the computer on the home page, whenever a group of yours has "two eyes", apply the diagonal test. On 9 × 9 the computer often finds false eyes; when your group dies, replay the end and look for the eye that was not real. If you play people on the online page, sign in on your account so games are saved for this kind of review.
Related: two eyes to live, eye shapes and vital points, how to study life and death.
A step-by-step check you can use in games
When one of your groups seems to have two eyes, run this check on each eye in turn:
- Find the eye point and list the stones that surround it.
- For each surrounding stone, ask: is it connected to the main group, or could it be cut off?
- If a surrounding stone could be cut off, count its liberties. If it could be put in atari, the eye is in danger.
- Apply the diagonal test as a quick confirmation.
It sounds long, but after a few days it becomes a glance. Players who do this habitually almost never lose a group they thought was alive — and they start to see opportunities to make their opponent's eyes false, which is where many life-and-death fights are won.
False eyes and the end of the game
Because every stone on the board counts at the end of a game on this site, false eyes matter all the way to the final count. A group with a false eye may survive until the last moves only because your opponent did not notice. Before passing, check your own weak groups once more; if an eye is false, fix it, because a careful opponent will capture the group before passing too.
False eyes in the centre
In the centre, an eye point has four diagonals. If the opponent occupies two of them, one of the stones around the eye can usually be separated and captured, so the eye becomes false. Centre groups are especially prone to this, because their shapes tend to be loose. When you build eyes in the centre, keep the surrounding stones solidly connected rather than linked by diagonals.
Practising the diagonal test
A simple drill: during your next few games, every time you see an eye — yours or your opponent's — glance at its diagonals and decide in one second whether it is real. At first you will need to check by reading. After a week, false eyes will start to look wrong at first sight, the same way a stone in atari starts to look wrong once you have learned liberties.
Frequently asked questions
Can a group with one real eye and one false eye live?
Not by itself. It effectively has one eye and can be killed, unless it connects to a living group.
Is the diagonal test always right?
It is a reliable rule of thumb. The underlying question is whether the stones around the eye can be captured.
How many diagonals does an edge eye need?
Both of its two diagonals, as a rule of thumb.
Can I turn a false eye into a real one?
Often, by connecting the stone that can be cut off or taking the key diagonal before the opponent does.
Why is attacking the diagonal so effective?
Because it can make an eye false without needing to fill the eye itself.
