A capped range is one that can no longer contain the strongest hands, because the player’s earlier actions would have been different with them. Betting into a capped range is how probes, thin value bets and value overbets make money.
Ranges get capped by passive actions. A flop call caps a range below the hands that would have raised — sets and two pairs often raise — so it mostly holds one pair, draws and floats. A check from the preflop raiser caps it more sharply: strong hands almost always c-bet, so the hands that check back are mostly medium pairs, ace-high and missed draws. A turn that went check-check is the clearest signal of all.
A capped range full of one-pair and two-pair hands is exactly the range that pays an overbet when you hold the top of what is possible, because those hands look too good to fold and are never good enough to raise. It is also the target of thin value: when villain checks a street on which his strong hands would have bet, what remains can call but not raise. The flip side is reading your own line: if every strong hand in your range would have raised earlier, your range is capped too, and a big bet from it is hard to believe.
Worked example
FAQ
What does capped range mean in poker?
It means the range has a ceiling: the strongest hands are mostly gone because they would have bet or raised on an earlier street. A player who checks back the flop as the preflop raiser usually has a capped range on the turn.
How do you exploit a capped range?
Bet into it. Probe the turn after the raiser checks back, bet thin for value after check-check, and overbet your nuts on the river when his line says he cannot hold them.