On OGS when scoring using AGA rules is area or territory scoring used? AGA states that either is acceptable. I am unable to find where it says which is actually used on OGS.
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Under AGA rules they are equivalent 
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It’s territory scoring. Basically the same as Japanese rules.
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My understanding was that the whole point of AGA rules was to make area and territory scoring the same. I believe this is achieved by the requirement that you give your opponent a stone as a prisoner if you pass and that white must be last to pass to end the game.
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Territory scoring and area scoring produce the same result regardless of what rule set is being used. And yes, under AGA rules you are required to give a stone to your opponent when passing in live games, but for the purposes of scoring online games AGA, Japanese, and Korean rules are basically indistinguishable.
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The scores are usually different, as territory scoring doesn’t include the occupied intersections and area scoring doesn’t include prisoners.
What remains the same is the score difference.
Yes of course, it’s the difference in scores that remains the same, not the actual scores
@StephenC20XX The difference in scores is very close, with correct play, but not always exactly the same. Which is the point of the way AGA rules are set up, so that they will always be the same, including with improper play.
@koolbreeze Fundamentally, AGA rules operate like area scoring. They allow you to do the counting either way you like, of course, but the difference in points will be the area-scoring difference, either way.
Most significantly, this includes situations where you have to play out a sequence to prove life or death. One player keeps playing in their own territory (losing a point), but the other player keeps passing (giving a point back).
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Thie suboptimal play was the point I wanted to know about. I am not that good, so in live games when I get into a time constraint I tend to throw a stone down on something that may or may not be a cutting or invasion point, (i.e. I don’t have time to read, but it feels weak) to solidify it instead of pass.
My understanding is that Japanese rules punish this with point loss while Chinese rules do not. I missed the point that AGA has a player give a stone to pass to negate this effect. So under AGA rules it does not matter if area or territory scoring is used since both do not punish unnecessary plays via the ‘give a stone to pass’ mechanism. Please correct me if I am misunderstanding though.
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This is only true at the very end of the game, when the only choice is to pass or play inside territories.
If there are still unoccupied neutral intersections, your opponent can occupy them, gaining points under Chinese rules.
This is only if the invading group(s) are agreed to be alive when counting. Otherwise they would be removed during counting, or played out and captured.
Neutral intersections, meaning empty spaces between actually living groups. In territory scoring, these are worth nothing, and you usually don’t even play them. In area scoring, these are worth one point each, and technically you should play them out (though often players still won’t bother). Of course, usually the players just split them evenly. Unless one of the players plays a move inside their own territory.
Imagine a 9x9 game where both players have claimed half the board, except for an empty line down the center. An exactly even split. Those 9 empty points in between? Those are neutral points. Under territory scoring, they are worthless, but under area scoring, they are worth one point each.
Now imagine that, instead of taking one of those points, you worry about an invasion in your territory, so you make a move to protect it. Under territory scoring, you have lost a point, because you played in your territory. But under area scoring, you have played a move that does not make or lose any points, and your opponent gets to claim an extra point in the center. So you fell behind by a point, regardless of which scoring system you use.
After all the neutral points have been filled in, there’s a difference. At that point, territory scoring still punishes you for protecting, but area scoring does not. But it’s extremely rare to be able to fill all the neutral points before worrying about a life and death question, so in general you should just treat unnecessary protective moves as a one point loss, every time.
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Under AGA with territory scoring, you shouldn’t pass when there are neutral intersections remaining, right? You have to give a stone to your opponent and then they can just play in one of the empty intersections. They don’t gain or lose points for playing in an empty intersection but you do when you pass.
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That’s correct. The AGA rules use area scoring, so the concept of dame being worth a point still stands. The pass stone exists so that you can use the territory counting method and get the same result.
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