Flinching

A flinch is the reflex all characters make when their current action is interrupted by an attack. The interrupted action is replaced with a short animation of being hit. The knockback dealt affects how strong the flinch is — weak attacks incur only a few frames of flinching, while stronger ones can deal about three times as much (and for some characters, even more if the characters are buried), but those strong enough to cause tumbling skip the flinch animation altogether. As a result, attacks that do not cause any knockback will not cause flinching, and neither will attacks that deal no damage.

As flinching is directly related to knockback received, increasing weight through a Super Mushroom, or using a move with knockback resistance will also make it more difficult to flinch. Flinching while charging an attack or special move will cause the charge to be lost, regardless of whether any charge had been saved previously.

Flinches can make characters vulnerable to combos, and the lag from them can sometimes guarantee a follow-up with a stronger attack or a grab. A prime example is the jab grab (also known as jab reset) in Super Smash Flash 2, although can do a similar technique in SSF2, or the jab-to-up smash combo that works with  in the same game.

Flinching does not strictly apply to characters. Starfy, a Assist Trophy, will flinch when attacked. Master Hand and Crazy Hand, both bosses in Super Smash Flash, also flinch when attacked.