Grab release is the animation that characters enter when they are freed from a grab without entering knockback. Normal grab release occurs after a certain amount of time if a grabbed character is not thrown (this time can be shortened by button mashing), but characters also enter grab release when the grabbing character enters hitstun or the platform they're standing on disappears. There are three main types of grab release animations: ground release, air release, and pummel release. Many combos can be performed by attacking when an opponent is stuck in the frames of their grab release animation. There are no grab releases in the original Super Smash Bros., where waiting too long will just result in a forward throw. The exception is Donkey Kong, whose forward throw can be mashed out of.
Types of grab release animations
Ground release is the animation a character enters when they break out of a grab sliding backward along the ground, along with a "letting go" animation. The grabbing character may slide back a bit as well. The distance sent is affected by the grabbing character and the victim's traction. A ground release causes both characters to be stuck in 29 frames (30 frames in the victim's case in Brawl) of ending lag where they cannot act, with a few exceptions (see below). A ground release occurs when the grabbed character's feet are touching the ground and not moving around while being grabbed. Since the grabbed character has an extra frame of ending lag in Brawl, they can be hit if the grabber has a frame 1 move with enough range (such as Squirtle's and Zero Suit Samus' jabs).
Air release is another animation a character can enter after escaping from a grab. In an air release, the grabbed character performs an arch-like movement backwards into the air, along with a "letting go" animation. The distance sent is character-specific and is mainly affected by gravity and air friction. Gravity will affect how high the character is sent (in Melee and Brawl) and how quickly they will start descending (in all games) while air friction determines how much horizontal distance a character will travel. Higher gravity will result in a character gaining less height and reaching the ground sooner. Likewise, higher air friction will cause a character to travel less horizontal distance. Much like with ground releases, the grabber is stuck in 29 frames of lag (except for Bowser in Melee and Brawl) although the amount of time the grabbed opponent is stuck in lag depends on the game. In all games, the grabbed opponent can force an air release by pressing the jump button or up on the Control Stick shortly before being grab released granted that the grabber is not pummelling them.
In Melee, the direction the grabbed character moves can be altered slightly by pressing left and/or right. An air release causes the grabbing character and the victim to be stuck in 29 frames of lag. An air release will only occur if the grabbed opponent forces it. Because of these properties, air releases are fairly inconsistent and have little practical use in competitive play. One character who can make use of air releases is Bowser as his grab release animation is only 19 frames long giving him 10 frames to act before his victim can. This can allow him to regrab his opponent if they are air released into a wall such as in Pokémon Stadium.
In Brawl, air release mechanics were heavily altered. The victim is now stuck in 50 frames of lag (49 in Jigglypuff's case) when being air released and the victim can no longer alter their trajectory by holding left or right. Because of this, the grabber now has a 21 frame advantage (31 in Bowser's case) when air releasing an opponent. In addition, an air release will always occur if the victim's feet are not touching the ground granted that the grabber is not pummelling. Taller characters tend to be able to air release more characters and are more vulnerable to ground releases, and shorter characters tend to be able to ground release more characters and are more vulnerable to air releases although there are exceptions. However, the grabbing height of a character can be different depending on the direction they are facing, as well as whether a standing grab, dash grab, or pivot grab is used; a character could be air released facing left and ground released facing right, and vice versa. Characters are also more vulnerable to air releases if they are grabbed in mid air. This can allow smaller characters to air release other small characters and it can allow taller characters to force more characters into an air release. Yoshi and Snake are unique as they can force the entire cast into an air release. Because of these changes, air releases can be abused far more making them a viable strategy in competitive play especially since most kill confirms out of throws were removed due to the general physics changes. While a majority of characters can be affected by grab release combos depending on the matchup, some characters can be abused more than others most notably Squirtle, Meta Knight and most of all Wario. On the flip side, some characters who can abuse aerial grab releases the most are Snake, Yoshi, Marth and Captain Falcon due to the former two having the most versatile grab releases while the latter two are fast and have good attack speed.
Grab release mechanics remained mostly identical in Smash 4 although one significant change is that the victim is only stuck in lag for 39 frames allowing them to act 11 frames sooner. Because of this, even fewer characters can be affected by grab releases and only a few characters can even get a grab release follow up in specific matchups. To further exacerbate this issue, the victim can no longer be regrabbed due to the removal of chain grabbing. Because of this, air releases are significantly less useful than they were in Brawl and are very rarely used as an intentional strategy in competitive play. Gravity is also no longer applied when a character is initially grab released causing most characters to travel the same height which notably hurts Jigglypuff. Prior to update 1.0.4, Wario had a similar grab release animation to Brawl (Mega Man also had a similar grab release animation) which could be abused albeit not to the same extent as in Brawl due to his reduced vulberability combined with his lower air friction sending him slightly further out although in both Wario and Mega Man's case, their air release animations were altered in version 1.0.4 with their normal air friction no longer applying when grab released making them far less vulnerable to followups.
The mechanics once again remain very similar in Ultimate although now, an air released opponent is stuck in lag for 29 frames like in Melee giving the grabber no advantage over the victim. This was likely done as the universally increased dash speeds and reduced jumpsquats would have opened more opportunities for grab release combos to be performed if the grabber had a frame advantage over the victim. This removes all possible guaranteed follow ups unless the opponent flies into an item with an active hitbox or a hazard. Snake is the only character who could feasibly use an aerial grab release to his advantage if his opponent lands into one of his self detonating explosives although this is extremely impractical to set up and feasibly achieve in a match especially compared to the simple followups he had in Brawl.
The pummel release is a type of grab release very similar to the ground release, but it occurs when the grabbed character is pummeled right when or right before they are grab released. A pummel release can occur even if the character would normally be air released, and a pummel release cannot be forced into an air release by pressing up or jump. The distance sent by a pummel release can be different than the distance sent by a ground release, as a pummel release will cause normally air-released characters to fall to the ground without sliding backward.
Other grab releases
When the grabbing character and/or the victim enter knockback, the victim will receive an additional 3%. If only the grabbing character is hit, the grabbed character will also enter an animation similar to a ground release.
If the platform the grabbing character stands on disappears, the victim will receive 3% damage and the grabbing character will be sent away in an arc similar to an air release.
If the grabbed character is lifted up by the platform they are hovering over, they will eventually break apart from the grabbing character and both characters will enter an animation similar to a ground release.
In Super Smash Bros. Ultimate, in the event that two characters attempt to grab each other simultaneously, both characters undergo a grab release animation and take 1.2% damage. In previous games, simultaneous grabs result in one character's grab being successful, determined by port priority (in Brawl and earlier games) or randomly (in Smash 4).
Notable grab release combos
Both chaingrabbing and grab release combos have been mostly removed in Smash 4 due to some core game mechanics being changed. Opponents are now immune to grabs for one second after being grab released and opponents can act out of an aerial grab release 10 frames sooner. However, there are a few exceptions.
Grab releases in the original Super Smash Bros.
Grab releases do not exist in Smash 64; a grab always lasts the same amount of time, and once that time is up, the character will automatically use a forward throw. Grabs cannot be mashed out of in this game, and the only way to escape grabs is if the victim is hit hard enough by a bystander's attack, in which case they will take the knockback of that attack. Donkey Kong's cargo release available in his forward throw may be considered a pseudo-grab release, due to DK losing hold of the opponent so they are vulnerable in front of him for a few moments (allowing techniques such as the infinite throw trap), but it is more of a way the throw works rather than an actual grab release.
It is currently unknown why Ness, Lucas, Jigglypuff, Bowser, and Donkey Kong have different grab release frames from the rest of the cast in Brawl. It is commonly believed that this was done to intentionally buff or nerf these characters, but there is no evidence supporting this, and many have stated that this is not an effective way to buff or nerf the characters.
The usage of grab release combos in tournaments has also been debated. Many claim that exploiting grab releases is an unfair disadvantage for the affected characters, as many of these combos can lead into guaranteed KO moves, and some are even zero-deaths and infinites. Grab release combos have been cited as the reason for Ness's and Lucas's lower tier placements throughout Brawl's history, and zero-death grab release combos in particular have been criticized for making certain matchups nearly unwinnable for affected characters. Others however, have argued that grab releases are a part of the game that must be dealt with and are an inherent strength/weakness to characters affected by them, and that they aren't functionally different from standard combos.
There have been some tournaments that have banned these grab release exploits (typically the grab release chain grabs on the PK kids), though this rule occurs only in fringe locals and has never been implemented in more major tournaments, as competitive players generally maintain that all techniques are fair game to use unless demonstrated to be broken. They also maintain that tournaments should be discouraged to implement rules just to arbitrarily buff or nerf certain characters and that "complex bans" should be avoided.
However, while competitive players generally accept grab release exploits, they generally don't like them, and as such, all the major Brawl mods have made efforts to remove all potential grab release followups.