A chain grab, also referred to as a chain throw or abbreviated as CG, refers to a form of infinite that is a series of grabs and throws that the victim cannot escape. Generally, a player throws the opponent in a specific direction (most commonly down or forward), chases the opponent's directional influence, then grabs the opponent in midair before they can tech. Sheik and the Ice Climbers are examples of characters who rely heavily on chain grabs. Due to the changes to hitstun and the more severe stale-move negation in Brawl, chain-grabbing is overall more prevalent. Generally, fastfallers, heavyweights, and large characters tend to be more vulnerable to chain grabs than floaty characters, lightweights, and smaller characters. Some circumstances can enable a chain grab to be a zero-to-death combo. The Ice Climbers are particularly potent at this. It is one of the two advanced techniques that were in the first three Smash games but no longer possible in Smash 4; the other is team wobble. The inability to chain grab (and team wobble, by extension) has been carried over into Ultimate, with fighters flashing yellow as a visual indicator of this mechanic.
Chain grabbing is a controversial technique within the community. Many players consider it an unsportsmanlike move because it can be inescapable when perfected by the grabber. It is additionally generally seen as "boring" even by competitive players to watch and play against, due to the repetition involved with repeatedly grabbing and throwing a character over and over while the opponent has negligible control in the matter, especially with prolonged chain throwing. Then since chain grabs tend to affect some characters a lot more severely, while for some other characters it is of negligent concern, it has a polarizing effect on matchups and is the primary cause for many hard counters. Infinite chain grabbing, in particular, has a tendency to encourage more defensive gameplay and camping tactics, especially in Brawl, another point of contention against chain grabbing. Since powerful chain throws can result in heavy damage or even a zero-death just from being grabbed, most players counter the risk of approaching opponents with access to such chain grabs by camping, either by staying airborne or on platforms.
However, competitive players generally see it as a valid technique and accept its usage, as it's simply a combo that is performed by grabbing, and that characters like Sheik, the Ice Climbers, and King Dedede need it to overcome other deficiencies in high-level matches, provided it is not used in extreme excess to stall (i.e. using King Dedede's standing infinite beyond 300% damage, which is well beyond the damage needed for Dedede to KO the opponent with his back throw). Competitive players additionally generally have a "play to win" mindset, meaning players are expected to utilize whatever legal means necessary in-game to win.
Possibly as a result of the controversy surrounding the technique, SSB4 has removed chain grabbing by granting 70 frames of invulnerability against grabs to a character who is thrown or grab-released. There is an argument about the change, but the general agreement is that it was for the best even in competitive play, due to the aforementioned polarizing effect chain throws tend to have on matchups, and them being generally regarded as spectator and player-unfriendly.
Characters with well-known chain grabs include the following.
The other main part of chain grabs can be seen on the "Combo Tent" portion of Hyrule Castle. Yoshi and Samus cannot do this due to their overly slow grabs (however, they can throw into a down aerial or a similar aerial to combo). Kirby, Ness, and Jigglypuff cannot do this due to their back throws having too much knockback to be able to combo before the opponent escapes hitstun. The majority requires down aerials and back throws. However, Pikachu, Fox, Captain Falcon, Mario, and Luigi can all perform chain grabs on this portion of the stage.
Super Smash Bros. 4 onward
Starting in Super Smash Bros. 4, characters are immune to any grabs for 1.1 seconds after escaping from a grab or being thrown (while the tips say they immunity lasts for only one second, the duration is actually 70 frames). This mechanic makes chain grabs virtually impossible to perform. Special moves involving grabs (such as Lucario's Force Palm and Kirby's Inhale) are also affected by this mechanic.
While grabs cannot directly combo into each other, it is possible to use attacks between grabs to keep the opponent in hitstun. Luigi, Ness, Sheik, and Roy are examples of characters with notable combos involving these pseudo-chain grabs. Additionally, Donkey Kong's cargo throws do not count by the game as grabs for this mechanic, allowing him to still chain grab opponents with his cargo down throw from low to mid percents when on a moving platform (such as Smashville's) or against a wall.
Super Smash Bros. Ultimate retains this mechanic from its predecessor, with a new yellow flashing visual to indicate when the opponent cannot be grabbed.