With no physical tells to go on when playing online the most pertinent information available to any player is an opponent’s betting patterns. It’s likely you’ve read somewhere that the easiest way to avoid giving off too much information is to keep your bet size exactly the same amount (in terms of big blinds) when first into the pot regardless of your hand strength or position. This gives off no extra info to an opponent and is the equivalent of having an online poker face made of stone. Fortunately for you not many people do this and the subtle differences they make in their bet sizing can tell us a lot about the strength of their holding. While it’s almost always impossible to put a player on a particular hand - it is possible to put them on a range and then play accordingly.
Two of the most common changes in preflop betting are when a player who usually opens to three times the big blind suddenly makes it either two times the big blind or four times the big blind. Both adjustments tell you a lot about the player’s probable hand strength, though obviously you also have to take their position and playing style into account.
Let’s look at the 2x raise first. When made from early position, this bet reeks of strength. This hand is almost always a monster and you can ditch your medium strength hands like K-Q. Most advice for tournaments and Sit & Go’s suggests you need approaching 15-to-1 implied odds to profitably set-mine, but if someone min-raises from early position you can shrink the implied odds you need to around the actual odds of 8-to-1 as you’re more likely to stack someone.
However, if the 2x raise has come from late position (especially if it’s a button min-raise) then it’s usually a sign of weakness and can be attacked if the situation and stack sizes are favourable.
Attacking 4x bets
At the opposite end of the scale if a player comes in for a 4x raise they’re almost always holding a good but not great hand. You can usually narrow their range accurately to 6-6 through J-J and K-Q, A-J – and occasionally even A-Q and A-K. So if you’re holding a premium hand then feel free to go ahead and jam it in if stacks are shallow or three-bet to induce a shove. Most weak players get stubborn when they’ve already invested a large amount into the pot.
The same principles hold true when a player three-bets you preflop. Obviously stack sizes are crucial but the general rule is that the smaller the three-bet in relation to your opening raise the stronger your opponent’s hand, and the larger it is the more marginal their holding.