Hitlag (also known as hitstop or freeze frames, and officially known as hitstun in Super Smash Bros. Ultimate) is a phenomenon that appears in all games of the Super Smash Bros. series, which involves attacks freezing the victim and (generally) the user in place for a certain amount of time when they hit.
If successful with most attacks, both the attacker and target are frozen in place for a certain number of frames; the attacker in the frame when they landed the hit, and the victim in the first frame of their flinching animation while shaking. This effectively extends the duration of the attack compared to if it had missed, while the target has a short time to react before the knockback occurs. Most noticeably, attacks with a large amount of hits such as Yoshi's down aerial take considerably less time to finish if they do not hit anything. As another side effect, the attack's hitboxes remain active during hitlag, thus extending its hit detection for targets other than the one hit; this can even be taken advantage of with damageable stage objects, such as the platforms in Skyworld, to allow attacks to hit opponents more easily.
Once hitlag has passed, both sides resume action. During hitlag, defending characters are capable of performing smash directional influence to get out of combos or multi-hit moves, or to increase their chance for survival.
Hitlag serves two primary functions. The first is a visual indicator that an attack connects; the brief moment where both fighters freeze gives both players more time to plan their next moves. The second is to add more emphasis to the power and impact of particularly strong attacks, which usually produce a high amount of hitlag. In several other fighting games, hitlag frames are often correlated to the power level of the connecting attack, ranging from light to heavy; Smash games achieve a similar hierarchy by giving attacks higher hitlag the more damage they deal (though this is more customizable in later games).
The formula for calculating the number of frames of hitlag experienced by both the attacker and victim has been different for most of the games (
The values correspond to the following (all apply to both the attacker and victim unless stated otherwise):
As shown by the formulas, the general amount of hitlag on moves is at its lowest in Melee, and has since increased throughout the series, with Ultimate having the most hitlag. In all games, hitlag is higher the more damage a move deals; weak attacks such as Mario's jab have minimal hitlag, but the hitlag of strong or sweetspotted attacks can last much longer. For example, a move that deals 15% damage with no other factors would inflict hitlag of 10 frames in Smash 64 (9 in the Japanese version), 8 frames in Melee, 9 frames in Brawl and Smash 4, and 15 frames in Ultimate. In addition, Brawl introduced the mechanic of hitlag multipliers, causing variance in the hitlag duration of attacks; this is in contrast to Melee and Smash 64, where the duration of hitlag was predictable.
A peculiar aspect of hitlag is how it is handled for throws. In Smash 64 and Melee, throws inflict no hitlag when releasing the opponent, but their pre-release hitboxes still do, such as those in Captain Falcon and Link's throws. From Brawl onward, throws can inflict hitlag on release, which only affects the opponent, effectively adding to their hitstun and giving the user more time to follow up; this is noticeable for throws such as Luigi's down throw in Smash 4, and Pikachu's down throw in Ultimate. However, hitlag remains manually disabled for the vast majority of throws' releases, especially in latter games (to the point Ultimate only has it on Mythra, Pikachu, and Pyra's down throws), leaving it as an uncommon advantage. In Ultimate, certain throws that lack hitboxes use an effect similar to hitlag before releasing the opponent, such as Marth's forward, back, and down throws; however, this effect has a set duration specific to each throw, and affects both the user and victim and makes the victim invincible alongside the user's natural throw invincibility.
As characters originating from other fighting game series, Ryu, Ken, and Kazuya have pronounced hitlag multipliers throughout a major part of their movesets, referencing the hitlag mechanics of their respective games. Ryu and Ken inflict above-average hitlag, with a multiplier of 1.5× for most attacks (1.8× for Ryu in Smash 4), while Kazuya's is below-average, with multipliers from 0.2× to 0.6× for most attacks. Notably, Terry does not have such a distinction.