Crouch cancel

Crouch cancel (or CC) is a term in the series which refers to the effect crouching has on getting hit. When a crouching character gets hit by an attack, they will suffer from less hitlag, as well as knockback in all games except Brawl, compared to any other action (besides shielding).
The term "crouch cancel" originates from various fighting games like , Soul Calibur, and Street Fighter Alpha 3, although the exact definition of the technique varies between games.
==In Super Smash Bros.==
In the original Super Smash Bros., crouch canceling reduces the amount of knockback and hitlag dealt to the opponent to 0.67x its normal amount. While the opponent suffers from 0.67x hitlag, the attacker still goes through their normal amount of hitlag, resulting in the opponent going into hitstun while the attacker is still in hitlag.
One of the main applications crouch canceling has is to survive stronger attacks. As crouch canceling reduces knockback, it can allow the opponent to survive attacks for much longer than they otherwise would be able to normally. For example, 's forward smash normally KOs another Mario at 102% from the middle of Dream Land however, if the victim Mario is crouching, the forward smash will not KO him until 178%. Crouch canceling also puts opponents into tumble at later percentages due to the lower knockback the victim receives, which can be utilised to avoid tech chasing setups. 
Another use crouch canceling has is to use the lower hitlag and knockback against the opponent. As the opponent has less hitlag and knockback, they recover noticeably sooner, which can allow them to avoid potential combos/multi hits which would normally work and they can even potentially punish the opponent after getting hit. This does overall depend on the strength of the attack, however. If combo oriented moves are crouch canceled, they can actually gain combo potential in scenarios where they otherwise would not combo. For example, 's Hand Slap usually has no followups against , as Jigglypuff is sent too high. If Jigglypuff crouch cancels the move however, it gets knocked back a much shorter distance, which allows Donkey Kong to get a guaranteed forward aerial against Jigglypuff. In addition to this, as crouch canceling gives the opponent less hitlag, this gives the opponent less time to SDI the attack they crouch canceled, making it considerably harder and less effective to SDI to potentially avoid followups (especially since the player is holding down when they get hit, making it more difficult to set up appropriate SDI).
While crouch canceling can be useful in certain situations, it is not an incredibly potent technique overall. While it does allow characters to live longer, characters may have better solutions in certain situations, such as shielding or counter attacking. As mentioned before, crouch canceling can be detrimental against certain moves allowing otherwise impossible combos and KO confirms to work against crouch canceling. Crouch canceling can also be beaten by grabs, as grabs get the opponent out of their crouching state, making it impossible to crouch cancel throws. and Jigglypuff can crouch under some grabs although this is separate from crouch canceling. Multi hits are also effective at beating crouch canceling as while the first hit of a multi hit will be crouch canceled, any following hits will function normally, making crouch canceling ineffective against multi hits. 
Crouch canceling overall can be useful in the right situations but it is not uncommon for opponents to have better options in situations where crouch canceling can be utilised and crouch canceling can be a hinderance when used in the wrong situations.
==In Super Smash Bros. Melee==
In Super Smash Bros. Melee, Crouch canceling functions in the same way as the previous game on paper, with crouching reducing the amount of knockback and hitlag dealt to the opponent to 0.67x its normal value. However, there are multiple universal changes in Melee which make Crouch Canceling a far more potent tool than in the previous game.
When a player lands while in non-tumble hitstun in Melee, the player will go into their normal landing animation, regardless of how long they have been in hitstun. This means that a move which would normally have 30 frames of hitstun can have as little as 4 frames of effective lag (for most characters, depending on the length of their landing animation). Melee also introduced traditional DI and when the player crouch cancels, they naturally DI downwards (as long as they are still holding down after hitlag ends). Both of these factors combined result in crouch canceling being incredibly potent. When the player crouch cancels a move which does not put them into tumble (and lifts them off the ground), they land as soon as they are no longer in hitlag as long as they are still holding down after hitlag ends, even for moves with a 90° launch angle. Even with weaker tumble knockback, the opponent will still immediately land on the ground. Because of this (at least for non-tumble knockback), most characters will only have 4 frames of lag from the attack rather than however much hitstun the opponent would normally have if they did not land on the ground. This also works in tandem with the game's higher tumble threshold, going up from 60 units to 80 units of knockback. In the context of crouch canceling, this means that the opponent can crouch cancel moves and stay out of tumble for considerably longer. In the most extreme examples, moves which can have 46 frames of hitstun with no crouch canceling and 30 frames with crouch canceling will have as little as 4 frames of lag when crouch canceled and DI'd down. This is naturally extremely potent.
Because of this, crouch canceling can not only be used to survive attacks for longer but it can also be exploited to make numerous moves unsafe on hit, allowing for many moves to be punished. While this could be done in the previous game, this is far more effective and can be done for far longer in Melee. With opponents not being lifted off the ground until much higher percents, along with the game's generally lower hitstun, crouch canceling does not open up new combo opportunities nearly as frequently (although it can still occur). In numerous cases, it can even allow the player to act earlier than if they shielded the move, with the player also having the benefit of having access to their entire moveset, rather than being restricted to their actions out of shield. One character who can notably take advantage of this is , who can easily use her down smash after a crouch cancel to punish opponents before they recover. 
Crouch canceling does have similar drawbacks to their previous game but they are overall nowhere near as exploitable. While DI'ing downwards after crouch canceling does mitigate some of the reduced knockback from horizontal attacks, players can hold up after crouch canceling to DI upwards to allow them to live for much longer. This can be tight due to the player quickly having to change their stick angle, especially with the lower hitlag, but if done correctly, it can enable characters to survive strong attacks for an extremely long time. 
There are still certain ways to counter crouch canceling. Grabs still reliably beat crouch canceling but with most grabs being considerably laggier than in the previous game, this does make going for grabs riskier against smaller characters. Another way to beat crouch canceling is with multi-hits, particularly ones which do not lift opponents off the ground. If a move is crouch canceled and the move does not lift the opponent off the ground, the opponent will stay in hitstun as normal, just with the 0.67x hitstun/hitlag like in the previous game. This can come from purely horizontal launching attacks (0° moves, including Sakurai Angle moves with < 32 units of knockback) or moves which launch opponents downwards (meteor smashes and spikes). This overall reduces the effect of crouch canceling against these attacks and with multi hits with non-upwards knockback (such as 's down aerial), if the first hit is crouch canceled, the next hit should hit the opponent before they can crouch cancel again (unless the move has too little hitstun to do so), making the move function normally and nullifying the lower hitstun the crouch cancel had on the move. 
Strong multihits can also punish opponents carelessly trying to crouch cancel. For example, 's down smash typically only hits once or twice but if the opponent tries to crouch cancel every hit, all five hits can connect, which can deal up to . This is technically avoidable as if the player crouch cancels Peach's down smash, they can act before the next hit comes out, which can allow them to shield or spot dodge the move and some characters can even interrupt or trade with the down smash if they have a fast enough option (assuming they are not in tumble percents, where they can then tech the move after getting hit). However, Peach's down smash is still known for being an effective move at dealing with crouch canceling, as the opponent has to act very quickly to avoid getting punished by consecutive hits and if they don't, they can eat a ton of damage.
Crouch canceling overall is a highly useful and exploitable technique in Melee as it not only allows players to live longer but it can also allow players to punish many moves they otherwise would not be able to. It is overall a very useful technique in competitive play and knowing how to counter it is equally as important.
==In Super Smash Bros. Brawl==
In Super Smash Bros. Brawl, crouch canceling has seen a rather significant change, as it no longer affects knockback, now only reducing the opponent's hitlag to 0.67x. This has removed one of the main uses of crouch canceling, as it can no longer to be used to allow the opponent to live longer. In fact, it theoretically hinders the opponent's ability to survive as they have usually have less time to SDI the move to end up in a more favorable position to survive. 
Not only does the opponent receive their normal amount of knockback but there are multiple universal changes which hinder crouch canceling's effectiveness further. With DI being removed for non-tumble knockback and with characters landing during their non-tumble animation no longer going into their landing animation until their non-tumble animation is finished, crouch canceling has lost the vital benefits which made it so potent in Melee. Even if these factors were still present, the changes to the Sakurai angle (with Sakurai angle moves not lifting opponents of the ground until the opponent receives > 60 units of knockback, as opposed to > 32 units) would have still made the technique less effective against a significant chunk of moves. The only benefit the technique still has is that it gives the opponent less hitlag, which does still make many attacks less safe on crouch hit than on normal hit (unless they possess no hitlag frames after the initial hit) but nowhere near as much as the previous two games, especially Melee. 
Crouch canceling can be used to make certain multi hits fail to connect properly, which can then lead to the user shielding and then punishing. In most cases however, the player is better off shielding in the first place, especially since shielding has the same accessibility as crouch canceling. Crouch canceling will also make paralysis moves have less stun as the lower hitlag multiplier from the crouch cancel is considered for the paralysis formula. This can give opponents using paralysis moves (such as with down smash or Paralyzer) less time to follow up but even for these moves, shielding is still the better option. 
Crouch cancelling is mentioned (though not by name) in the Brawl manual, stating that crouching "...stabilizes you, reducing the chances an attack will knock you back." This is more in line with the technique's behavior in other installments than in Brawl, however.
Overall, crouch canceling has lost almost all of its utility in Brawl due to a combination of no longer reducing knockback and universal changes reducing its effectiveness. It has now become an extremely situational technique, with shielding almost always being the better option.
==In Super Smash Bros. 4==
In Super Smash Bros. 4, crouch canceling not only still deals 0.67x hitlag to the opponent but notably, it once again reduces the amount of knockback the opponent takes, although not to the same extent as the first two games. The opponent's knockback is reduced to 0.85x. While this does make crouch canceling worse for survival than in Smash 64 and Melee, it does still allow the player to survive attacks for longer. For example, Mario's sweetspot forward smash KOs another Mario at 98% in the middle of (with no DI) but if the opponent Mario crouch cancels, it does not KO until 124%. While this can be useful, shielding is generally the better option in KO situations, especially if the player performs a powershield. The lower hitlag received from crouch canceling can also be more beneficial against non-KO moves, as many attacks have higher hitlag multipliers than in Brawl, sometimes significantly so, although this is move dependent. 
In terms of utilising crouch canceling to make attacks less safe on hit, it can still be done but it is nowhere near as effective as in Melee or Smash 64. The lower difference in knockback makes it less effective than in Smash 64, while this along with various universal changes (the removal of DI for non-tumble moves, characters no longer going into a landing animation after landing during non-tumble hitstun among other changes) makes it considerably less effective than in Melee, especially since the player has access to shielding. Nevertheless, it can still be done and there are specific cases where it may be more optimal than shielding.
With crouch canceling once again reducing knockback, this also means that the lower knockback can be disadvantageous in certain scenarios. It can not only allow for certain KO confirms to work at percent ranges they normally would not but it can also make some multi hits connect more reliably. For example, if has rage, the close hitbox on the first hit of his down smash will put his opponent into tumble, which allows them to DI the move down and then tech, to avoid the second hit and even punish Cloud afterwards. If the opponent crouch cancels however, they will not be put into tumble by this hitbox (even if Cloud has maximum rage), which will allow it to reliably lead into the second hit. 
 can uniquely take advantage of crouch cancelling with Tough Guy, his unique form of passive knockback-based armor. This can cause certain attacks to not deal any knockback to Bowser when they ordinarily would, which can allow for unique punishes. This only effectively works for an extra 3-4 units of knockback, so it is not highly applicable but it can be applicable in certain scenarios. 
Crouch canceling also has an even greater affect on paralysis moves as both the reduced knockback and hitlag are considered in the paralysis formula. This results in crouch canceling reducing the duration of paralysis moves to 0.5695× (rather than 0.67x in Brawl) which is naturally beneficial.
Overall, crouch canceling is more effective than in Brawl, although it still remains a situational technique overall. In cases where crouch canceling can be useful, shielding is generally the better option overall outside of specific cases, though crouch canceling still has its advantages.
==In Super Smash Bros. Ultimate==
In Super Smash Bros. Ultimate, crouch cancelling mostly functions the same as the previous game with attacks dealing 0.85x as much knockback and 0.67x as much hitlag. However, the attacker's hitlag is now also reduced by 0.67x. This overall reduces the effectiveness of crouch canceling as in most cases, the opponent no longer enters hitstun while the attacker is still in hitlag, reducing the additional frame advantage the opponent receives. With weaker attacks, this reduces the amount of extra time the opponent has to punish the attacker, while with slightly stronger attacks, it gives the attacker more time to follow up into a potential kill confirm. Additionally, many attacks in Ultimate generally have much higher base knockback than in previous games (especially Smash 64 and Melee), reducing the amount of moves that are unsafe on hit in the first place, heavily nerfing one of its strongest aspects. 
Crouch canceling still has the same uses as the previous game but it is less applicable when it comes to punishing moves or avoiding followups due to the attacker's lower hitlag. Characters who possess constantly active passive armor ( and newcomer ) can utilise crouch canceling to allow them to armor slightly stronger attacks. Bowser can utilise crouch canceling for longer in this context due to his greater weight and higher armor threshold and Kazuya has access to a variety of attacks that can only be used while crouching, allowing him to make use of crouch cancelling (even without his Tough Body armor), more often than most other characters. 
Overall, crouch canceling is just as situational of a technique in Ultimate as it was in the previous game, if not more, but crouch canceling can still be useful, especially for specific characters.