Special Zoom activates when a fighter is hit by certain attacks: the background flashes blue with dramatic "spark" effects pointing towards the impact. If there are only two players on screen, time substantially slows down and the camera zooms in on the impact. The slowdown only lasts for a short moment in 1v1s and is even shorter in games with more than two players, and is usually accompanied by the sound effect previously only used by Little Mac's KO Uppercut in Super Smash Bros. 4. (KO Uppercut previously had its own slowdown effect, but now uses Special Zoom along with Cloud's Limit Break special moves.)
During some Special Zoom events, camera control is disabled, though this is not consistently enforced.
In general, the attacks that trigger Special Zoom are slow and hard to hit with (such as Warlock Punch or Falcon Punch). Most other attacks that trigger Special Zoom have conditions that need to be met, such as Ridley's Skewer needing to be sweetspotted, or Little Mac's smash attacks requiring his armor to be triggered during the start-up. Certain items and stage hazards may also trigger Special Zoom, also requiring special conditions in some cases.
Special Zoom occurs even if the attack's knockback is negated by armor. However, Special Zoom will not trigger if the opponent is hit while invincible, during the last five seconds in a time match or when hitting the AI-controlled character of the Ice Climbers.
Similar to Special Zoom is Finish Zoom or Final Zoom, terms also coined by Sakurai and his team. Finish Zoom is used when an attack will likely result in a game-winning KO. Like the Deadly Blow mechanic introduced in Super Smash Bros. 4, this effect does not factor in DI being used to make an otherwise-deadly blow survivable. Like Special Zoom, Finish Zoom zooms in on the point of impact and briefly slows down time. However, Finish Zoom uses a red background instead of a blue one, and the sound is always the same. The sound used is also different again, being akin to a ping hit combined with the sound of slashing swords. Screen KOs rarely occur when a Finish Zoom sends an opponent into the upper blast line, while Star KOs are very rare.
List of moves that trigger Special Zoom
By assist trophy
By stage hazard