V-cancelling, or velocity cancelling, is a technique that decreases the knockback velocity of moves in certain situations. This is done by hard pressing the L button or R button 1 or 2 frames before the hitboxes collide, or on the same frame that the hitbox collides. In order to V-cancel, a player must be in the air, not in hitstun, not in an attack animation, and cannot have hard pressed the L or R button within the last 40 frames. V-cancelling reduced the initial knockback velocity to .95x the original, meaning that the decrease in knockback is 5%. The difference is small, but can be useful in dire situations.
It was documented by Achilles1515 in September 2015.
V-cancelling can be used along with other techniques such as DI and Smash DI to reduce knockback distance. Despite not being as effective as the other two techniques, it can be critical for surviving attacks that would otherwise result in a KO. For example, Fox's up smash can usually KO Falco at around 88% on Pokémon Stadium; however, with proper DI used in conjunction with V-cancelling, he can survive up to 102%.