Joseki - How to contest the corners
A joseki is a line-of-play (or “variation”) that is considered best play for both sides.
These are typically patterns that come up often in professional play.
While “joseki” usually refers to corner variations, they can be for any area, but in this lesson I’ll be discussing the corners only.
Also joseki are typically for the 19×19 board.
There are hundreds or perhaps thousands of joseki but you don’t need to worry about memorizing them. Just try to understand what’s happening and gain a feel for them.
To claim a corner, a player typically plays either the star point (at Q4), 1 or 2.
A is the same as 1, and B and C are special strategies that aren’t seen very often.
Hoshi
Hoshi (“The star point”, “4-4 point”) is the most outward-facing of the points, and looks to establish a balance between territory and influence.
Invasions into the corner are possible for white but black will get influence.
A-C are the most common follow-ups for black to enclose the corner.
A is more territory-oriented.
B makes it slightly more invadable but projects influence and is useful when building a moyo.
C is a fast move that threatens to make big points or great influence if white decides to invade at the 3-3 point.
Of course, you can play A-C on the either side because it’s symmetrical.
Let’s look at what white is considering.
A-C are common ways to approach this corner.
Let’s look at the invasion at C.
This is a typical way for white to invade and live in the corner. Black is left with a wall with influence facing the center and both sides so it’s usually an even exchange.
White also takes sente (i.e. white both started and ended the joseki with the initiative) so that’s nice.
White 2 is a common approach. Black makes a strong shape with 3. White pushes into the corner and black defends it with 4 & 5.
Finally, white plays 6 to make a base.
If black plays 3 at 4, white plays 4 at 3, preventing black from efficiently extending along the sides.
If white omits 6, black can attack the 2 white stones at 6.
Komoku
Komoku (“3-4 point”) is more territorially-focused then hoshi and prevents an easy invasion of the corner.
Notice that, unlike hoshi, the komoku can only really extend one way because extending instead towards the left would not efficiently surround points in the corner.
A is a very solid enclosure.
C asks for a little more but leaves more aji.
B is a little more influential and works well with moyos.
D is a flexible shape that can take a large corner or be invaded and receive a wall on the outside.
Likewise, the approaches should usually come from this side.
Approaching from the left would allow black to play A or B and efficiently surround the corner.
Let’s look at a common joseki. 3 looks to take the corner straight away.
White defends with the hane at 4. Black defends at 5. After that the cut at 6 is strong for black so white defends there.
Black plays 7 to not be sealed in the corner.
White then plays an extension along the side.
If black omits 7, white can play A and seal black in.
If white omits 8, black can attack white’s three stones with B.
These were just a few example josekis and ideas for how to play corners and contest them. Again, memorizing them isn’t as important as understanding what’s happening during them.
Check out josekipedia if you’d like to see more josekis but make sure you don’t use it during a game unless your opponent is ok with it.