Subtick is a system that Valve introduced in CS2 to replace the tickrate familiar from CS:GO. Previously, the server updated the game state a fixed number of times per second, and all player actions — a shot, a jump, a change of direction — were rounded to the nearest tick. At a tickrate of 128 (that is, 128 updates per second), this rounding was almost unnoticeable, but it still existed: if a player pressed the fire button between ticks, the server would "shift" that action to the next update.
Subtick works differently: the server records the exact time within the tick interval when the action occurred and processes it based on that timestamp. According to the developers' intent, this should eliminate rounding altogether and make hits and movement more accurate than with any fixed tickrate, even the highest one.
Why the topic sparked debate
It was this gap between theory and practice that one captain from the post-Soviet scene highlighted when he admitted he missed the 128 tickrate from CS:GO. Some professional players complain that on subtick, the feel of shooting and movement differs from what they're used to — some call it a "rubbery" feeling of control, while others note instability in hit registration in certain situations. Developers continue to make adjustments to how subtick works through patches, but the controversy around the topic doesn't go away — a team accustomed to CS:GO perceives any deviation from the familiar model as a potential threat to the stability of the mechanics on which high-level play is built.
For the average viewer, the difference between tickrate and subtick is invisible, but it's exactly these details that shape professionals' perception of the game at the millisecond level — trade timings, spray control accuracy, retake reactions. That's why the discussion around subtick isn't an abstract technical dispute, but part of a broader conversation about how the transition from CS:GO to CS2 has changed the very mechanics of the game for those who make their living playing it.