Armor

Ike's super armor from his Aether move. Notice how Ike didn't take any knockback from Critical Hit, which is an invariable OHKO under standard circumstances.

Armor, also called launch resistance, knockback resistance, super armor (for infinite knockback resistance), or heavy armor (for finite knockback resistance), is an effect of certain moves or actions in all four Super Smash Bros. games. When a character has armor, they will take less knockback than usual, or (for super armor) not flinch at all. The effect of all types of armor only affects knockback; the attack's full damage will still be taken. Most cases of armor provide an infinite amount of knockback resistance; comparatively few provide only a finite amount. Armor can also be known as light armor if it only protects against extremely weak low-knockback attacks, such as jabs or individual hits of multi-hitting attacks).

An unrelated phenomenon with similar effects known as faux super armor occurs when two characters are hit with the same hitbox while one has the other in a grab. When this occurs, whoever has higher controller port priority takes full damage but only flinching slightly from the attack, while the other takes full damage and full knockback.

In Super Smash Bros. and Melee, when a grab connects with a character that also has an active hitbox, the character that attempted the grab will override the hitbox completely (taking no damage or knockback) and proceed with the grab. In Brawl, the same character takes the damage from the hitbox but not the knockback, giving the illusion of "grab armor", though it is not to be confused with true launch resistance, as this will only occur if the grab actually connects with the other character's hurtbox. In Smash 4, this situation is reversed; the character that attempted the grab will now take full damage and knockback from the hitbox, and the other character will only flinch slightly and take 3% damage or more, depending on the type of grab that was used.

Note that grab hitboxes ignore all variations of armor (as the grab itself produces no knockback), and many bosses (except Giga Bowser in Melee and Master Core's final form in Smash 4) cannot flinch or be knocked back at all, effectively giving them permanent super armor.

In Super Smash Bros. and Super Smash Bros. Melee

Yoshi double jumping through an attack.

Armor is a very uncommon occurrence in the first two games, being limited to Yoshi's double jump cancel counter and crouch canceling, which will reduce knockback to 2/3 of the original value in Smash 64 and "Melee" (at the cost of poor survival directional influence). The difficulty setting on the single player modes (and events in Melee) also affects the ability to be launched for both the player's character and the CPU characters, with the player's character taking more knockback and the CPUs taking less knockback as the difficulty setting increases. Adjusting the handicap levels in the multiplayer modes in Melee has the same effect.

According to the Japanese Super Smash Bros. website, Yoshi's double jump resistance works by subtracting 120 from the knockback that would have been delivered, with Yoshi not flinching if the result is negative, and Yoshi taking the difference in knockback if the result is positive.

In Super Smash Bros. Brawl

Armor was formally introduced in Brawl; several characters have moves that provide them with infinite launch resistance, usually to allow for such characters to counter attempts to disrupt the incoming attack. Some of these moves are not offensive, however, and there are a few cases of finite launch resistance, as listed below. Crouch canceling no longer affects knockback, but instead affects the amount of freeze frames sustained.

All of the moves are super armor unless otherwise stated.

Character	Moves	Conditions and Notes
Bowser	Giga Bowser	Giga Bowser: For the entire period of being Giga Bowser.
Diddy Kong	Rocketbarrel Boost	Only the grounded version (this is a variation of heavy armor).
Donkey Kong	Giant Punch, Spinning Kong and Carry Throw	Giant Punch: only if fully charged; while moving his arm forward but the attack needs to make contact with his left arm and before it is released. Spinning Kong: only the grounded version; just before he starts to release it (frames 10-16 first hitting on frame 19); if he leaves the ground with Super Armor frames when using the grounded version, a glitch will make the Super Armor frames last for the entire move. Carry: DK gains knockback-based launch resistance for the entire duration of the Carry. Also works while holding heavy items.
Ganondorf	Flame Choke	In the grounded version, when holding the opponent off the ground; the opponent also gets super armor. In the aerial version, the opponent gets super armor but Ganondorf does not, allowing for strange KOs in places like Norfair or Brinstar where Ganondorf will bounce off the acid, while the opponent will continue their plummet.
Ike	Aether and Eruption	Aether: After throwing his sword in the air, but before he leaps up towards his sword. Eruption: Some frames after the special move button is released but before the sword hits the ground.
King Dedede	Super Dedede Jump	From the start until just before the apex of the jump.
Kirby	Stone	The entire duration of the period Kirby is in his Stone transformation, where he will take no damage or knockback, but he can only take up to 29% damage per Stone before he actually sustains knockback. If Kirby takes 30% (or more) damage during a single Stone transformation, he'll be knocked out of Stone and will take the full knockback -- but strangely none of the damage -- of that hitbox (this is a variation of heavy armor).
Olimar	Pikmin Order	During the first few frames. Lasts until right after he puts his head down.
Pit	Mirror Shield	Grounded version only; while pulling the shield out: frames 4-6.
Pokémon Trainer	Fly and Squirtle's forward smash	Fly: The beginning of the ascension times: Frames 4-13, making it useful when jumping out of shield and an effective combo breaker. Squirtle's forward smash: While moving forward.
Snake	Cypher	Snake cannot be flinched by any hitbox that deals exactly 7% or less, regardless of the knockback of the individual hitboxes. Most multi-hit moves deal less than 7% per hit, so they typically cannot interrupt the Cypher (a variation of heavy armor). (See this post and this followup post on SmashBoards for more details.)
Wario	Forward smash and Wario Waft	Forward smash: While moving forward: frames 8-12 Wario Waft: When fully charged, during the first few frames.
Yoshi	Double jump	Yoshi gains (approximately) 3860mph-worth of knockback resistance, as measured by the post-Brawl stats (under the "top launch speed"). This means that Yoshi will ignore any knockback that would launch him at less than ~3860mph while in his midair jump. As he is damaged, he takes more knockback from an attack with the same launching power, meaning that weaker attacks will begin interrupting his midair jump as Yoshi approaches higher percentages (a variation of heavy armor). (See this post on SmashBoards for more details.)

In Super Smash Bros. 4

Smash 4 continues the trend of implementing launch resistance to certain characters, though there is more variation with the strength of armor (some negligible, some infinite, and some based on damage). Crouch canceling now acts as a combination of Melee and Brawl's version of the tactic, although the knockback sustained is only reduced to 6/7 of the original value.

All of the moves are super armor unless otherwise stated.

Character	Moves	Conditions and Notes
Bowser	All animations and Giga Bowser	Bowser has universal light armor against attacks that deal negligible knockback. Giga Bowser retains the infinite knockback resistance from Brawl.
Bowser Jr.	Clown Kart Dash, Grounding Dash	Clown Kart Dash: It has a heavy armor to moves that deal no more than 7% of the damage. Grounding Dash: During the startup of the move.
Charizard	Rock Smash, Rock Hurl, Fly, Rising Cyclone, Flare Blitz and Blast Burn	Rock Smash: During the move's start-up, starting from frame 5. Is negated if the boulder is broken before Charizard headbutts it. Rock Hurl: Same as Rock Smash, except the super armor starts on frame 1. Fly/Rising Cyclone: Just like in Brawl, it has super armor during the move's start-up. Flare Blitz/Blast Burn: During the active charge portion of the move, it has heavy armor, where it'll armor through hitboxes that don't deal more than 14% damage.
Dark Pit	Electroshock Arm	Gains super armor during the uppercut.
Donkey Kong	Giant Punch, Spinning Kong, Stubborn Headbutt, Kong Cyclone and forward throw	Giant Punch: Only receives full super armor when the move is fully charged, when his arm is moving forward just before and during the punch (on frames 11-20). Spinning Kong: Only the grounded version, DK gains super armor when he pulls back or just before he starts spinning (frames 8-17, first hit on frame 19). Stubborn Headbutt: Gains super armor for the entire move, including start-up. Kong Cyclone: grounded version - from the 2nd hit in front until shortly before the last 2-3 swings; the aerial version seems to be the same case. Forward throw: Gains knockback-based heavy armor for the entire duration of carrying the opponent or object (i.e. boxes, crates etc.)
Ganondorf	Warlock Punch, Warlock Blade and Dark Fists	Warlock Punch / Warlock Blade: When initiated on the ground, the move will have super armor until Ganondorf begins his punch/thrust forward; also has super armor even when reversed. Does not have super armor if initiated while Ganon is airborne, even if Ganondorf lands on the ground before punching. Dark Fists: During its start-up, from frame 6 to 16 (when the hitbox of the first punch comes out).
Ike	Eruption and Aether	Eruption: Only gains super armor 3/4 to fully charged: shortly before the release (ends before hitbox appears) (frame 6-10). Aether: Gains a brief duration of super armor while his sword is thrown upwards (frame 18-21).
King Dedede	Super Dedede Jump, Rising Dedede and Armored Jet Hammer	Super Dedede Jump/Rising Dedede: Just like in Brawl, it has super armor during the rising portion of the move, until Dedede reaches the apex of his jump. Armored Jet Hammer: Once Dedede starts charging the move, it has super armor until Dedede unleashes the move or is interrupted by other means.
Kirby	Stone, Grounding Stone, Meteor Stone, Hammer and Giant Hammer	Stone/Grounding Stone/Meteor Stone: Kirby can sustain up to 24% damage while transformed, where he'll take no knockback from all moves regardless of how strong their knockback is, while also taking no damage. Once he sustains more than 24% damage while transformed, he'll be launched as normal, while taking half the damage from the threshold-breaking hitbox. This is a variation of heavy armor. Hammer: When fully charged, it'll have super armor during its swing. Giant Hammer: Once Kirby begins charging the move, he'll have super armor until the frame he unleashes it or until he is interrupted by other means.
Little Mac	Straight Lunge, all smash attacks and Giga Mac	Straight Lunge: Gains percent based heavy armor during the charging and execution. (damage based) KO Punch: Has super armor when the punch comes out but only for 1 frame. Smashes: Has super armor during their start-up. Giga Mac: The entire duration of the Final Smash.
Mii Brawler	Ultimate Uppercut and Exploding Side Kick	Ultimate Uppercut: During the start-up of the punch, only if fully charged. Explosive Side Kick: During the start-up, before kicking.
Olimar	Pikmin Order	Pikmin Order's armor frames are lesser than it was in Brawl.
Pac-Man	Power Pellet	Towards its end.
Pit	Upperdash Arm	During the uppercut.
Roy	Blazer	Has super armor on the grounded version during startup.
Ryu	Focus Attack	While charging the attack, Ryu will armor through a single hitbox that doesn't deal more than 39% damage, while also sustaining half the damage of the hit, but he will still be hit as normal (interrupted) if struck by a second hitbox regardless of damage/knockback. This is a variation of heavy armor albeit the strongest.
Wario	Wario Waft	During the startup when fully charged. (frames 5-10)
Wii Fit Trainer	Volatile Breathing	During the startup of the move.
Yoshi	Double jump	Yoshi retains the knockback-based heavy armor from Brawl.
All characters	Home-Run Bat and Ore Club	Home-Run Bat: When the bat is about to be swung. Ore Club: When charging and releasing a smash attack.

External references

• A better 'Super Armor List' Thread: lists characters and their moves that have Super Armor, along with some frame data.
• The Armor Project: explains how knockback-resisting moves that are not super armor work, including Snake's Cypher and Yoshi's double jump.