Lag Cancel

In all Fighting Games, each attack you do has a lag time or recovery; the amount of time after you make that attack that you cannot make another attack. After you throw a punch, there may be a second or two wherein you cannot throw another punch, to stop you from just hammering the punch button and throwing out fifteen punches per second.

In almost all Fighting Games, there are actions that you can perform while in recovery that reset the recovery, allowing you to attack again before you would normally be able to. Usually this allows you to still dodge, block, jump, duck, etc. even though you can't attack, so as not to leave you defenseless. The side effect that experts in fighting games seek is that they can attack again after performing this action, thereby shortening the recovery time between their attacks.

These recovery-shortening actions are known as canceling.

For example, let's say that you have a special attack called Punch Rush, and that after you do a Punch Rush you are in recovery for one second. Ducking takes half a second. It also resets your recovery. Therefore, if you Punch Rush and then, immediately after hitting your opponent, duck, and then Punch Rush again, you were able to "cheat" the system and punch-rush after only one second instead of three. This would be referred to as a Punch Rush Cancel or Punch Rush Canceling.

Of course, in real examples the time is much shorter.

This trope is almost completely ubiquitous in Fighting Games, though is by no means exclusive to them.

It might also be worth noting that, when used in a platforming or action title, dash canceling or jump canceling can be used to make your character move absurdly quickly. Often this requires frame-perfect timing, meaning that this can only be performed with any consistency in a Tool Assisted Speedrun. Compare Re Stabilization for Knockback cancelling.

Fighting Games

 * Street Fighter III allowed you to cancel certain attacks with a super jump which allowed you to extend some combos. These carried over to characters with super jumps in Street Fighter IV.
 * Street Fighter IV allowed you to cancel certain special moves with a Focus Attack and then cancel that attack with a forward or backward dash. "Focus Attack Dash Canceling" (or FADC for short) became a very important part of the game's early metagame since it allowed certain characters to combo reliably into their Ultra Combos.
 * C. Viper in particular can cancel/feint her Thunder Knuckle and Seismic Hammer specials by pressing any two punch buttons. Some of her more damaging combos use these heavily.
 * Many cancels exist in Super Smash Bros. The most famous non-character specific cancels is Z-Canceling/L-canceling in 64 and Melee respectively, where most air moves can be have the landed lag removed by shielding at the right time. Snake is somewhat known for this in Brawl, thus coining the term "Snakedashing".
 * Marvel vs. Capcom 3 has X-Factor, which will cancel ANYTHING that's not a straight cutscene. The catch is that it can only be used once per match. Some other noteworthy cancels include:
 * Morrigan can use Flight to cancel a Soul Fist (L or M) and then cancel Flight with Soul Fist H, giving her some zoning possibilities.
 * C. Viper can cancel three of her four (five in Ultimate) special moves just by pressing the Launcher Move button. The advantages of this vary depending on the move.
 * Dante's Bold Move is the only move that can be cancelled out of his Stinger move; Bold Move can also be cancelled into any special move if you're quick enough. Thus, many advanced Dante combos involve Bold Move cancelling out of Stinger and into other special moves. This can prove to be quite Difficult but Awesome.
 * Iron Fist can cancel his special moves into other special moves. Using this, he can chain up to three special moves together, having more options on the third move. The only catch is that he can't chain a special move into the same one.
 * Ultimate Marvel vs. Capcom 3 has Heroes and Heralds mode, which introduces some ability cards that allow players to cancel moves in ways not available in the normal game (dash cancel, jump cancel, special cancel, and so on), usually at the cost of Hyper Combo meter.
 * In Final Fantasy Dissidia, you can cancel dodges by attacking, and conversely cancel attacks by dodging.
 * Laguna's Ex-mode's passive effect cancels out the lag between his moves, letting him chain them together and taking his fighting style to the logical extreme.
 * Arcana Heart allows you to pull homing canceling.
 * Guilty Gear's version is called a "roman cancel". They're very costly (half of a full tension bar), but each character has moves that can be cancelled at a very specific point with only 25% tension bar cost which is called "Force roman cancel". Jam's card abilities allow her to cancel certain attacks to combo into whatever attack she has a card for.
 * Its Spiritual Successor Blaz Blue has Rapid Cancel, effectively the same mechanic as Roman Cancel, but Force Roman Cancel is removed. Hakumen's specials can be freely canceled into one another, but only as long as his Magatama gauge holds out.
 * Some fighting games take this one step further with a jump cancel cancel. You do a move, cancel it into a jump, then cancel the jump into another move before you leave the ground. It's easier than it sounds, you do the directional input for the attack, then input "up", then press the attack button before the game forgets the input. For example, to JCC an attack into a move with a quarter circle forward motion, you simply extend it so that you end with a diagonal up-forward input before you input the attack button for the second attack.
 * Naruto Shippuden Ultimate Ninja Storm Generations has added in a new cancel called the Chakra Dash cancel, which is done by pressing the triangle button which activates a character's chakra and pressing "X", which is normally the jump button. This will allow any character to cancel a combo into another combo seamlessly, and is a good way to do a massive amount of damage in a short period of time, but takes out a bit of chakra to do, and can't be done anymore until you charge your chakra back up.
 * In Touhou Scarlet Weather Rhapsody/Hisoutensoku, canceling is an integral part of game play, as it can allow players to rack up mean combos. And the rules are fairly simple: you can cancel into more powerful attacks. So a B-button attack can be canceled at any time into a C-button attack, which can be canceled into a Spell Card.

Other

 * In Defense of the Ancients, this technique is considered a critical part of the balance of the game, especially for heroes with ranged orb attacks i.e. Sacred Warrior, Netherdrake, Enchantress, etc. Drow Ranger's manual-casting of the orb effect plus animation-cancelling allows her to chase down any hero during the early game, even past towers.
 * In Metroid Prime it was possible to cancel missile lag by firing your normal beam, allowing you to fire missiles at a much faster rate than normal.
 * Melee attacks in Borderlands, for both slow firing weapons (but not Sniper Rifles since you need to aim) and reloading (as soon as the magazine/clip is inserted).
 * In Dungeons and Dragons Online, tumbling moves (unlike regular blocking) cancel a melee attack. Many enemies in the game have nasty special attacks with longer animations. The fact that it's possible to instantly roll away from one of these, whereas blocking has to wait until the character's attack and follow-through is over (and both are safer than fighting while running), is one reason why many character builds go cross-class to get 1 rank in the Tumble skill.
 * The original Tomb Raider games have many different ways to cancel recovery times from different moves, and working out ways to fit them in using level geometry is one of the main parts of most speedruns for them.
 * Steel Battalion has clip dumping. Main weapons will have a firing delay after firing a set number of rounds-one for smoothbore cannons, three for rapid-fire rifles, and five for assault rifles. By holding down the main weapon button such that the initial weapon switch selects the desired weapon (it won't cycle after that) and hitting the magazine change button, one can cancel the delay-but weapons only get three to four clips maximum, with 20 to 30 rounds each, thus burning a lot of spare ammo for an extra shot in quick succession! Furthermore, it's a very frowned-upon tactic in the Line of Contact community and will likely earn the ire of other players unless specifically permitted before the match. (Matches likely to have voluntary clip-dumping could be one 3rd-gen VT like an Earthshaker vs. several 1st-gen V Ts.)
 * In a very rare RPG example, Wild Arms 3 features an Animation Cancel. As long as you have at least 25 Force Points, you can cancel the move you just queued at that character's turn to move, enter another move and you will start your action without waiting. While not often used, it is important if you suddenly want to stop attacking the enemy for whatever reason (the enemy is preparing an instakill move, or a reflect barrier, for example).
 * A huge part of God of War's combat system is the ability to cancel Kratos' standard blade combos with a press of the block button, so if the player is fighting a Mook and his buddy attacks, one can quickly press the block button without breaking the combo.
 * Some classes in World of Warcraft can obtain a kind of passive cancel. One example is the Elemental-spec Shaman's Lava Surge talent. The damage ticks of Flame Shock, a damage-over-time spell, have a 10% or 20% chance (depending on the rank of the talent) to immediately end the cooldown on your Lava Burst spell. Since Lava Burst is guaranteed to land a nasty Critical Hit on a target suffering Flame Shock damage, this talent will provide huge boosts to your damage output when it's feeling generous.
 * Call of Duty games also have this. All firearms have their clip reloaded before the animation ends, so it's usually interrupted with melee attack or weapon switch (especially the fast-switching pistols). Especially valuable for slow-paced machineguns or notably longer empty clip reload animations.
 * Before Halo came out, most shooters (including CoD) didn't let players interrupt animations like reloading and attacking at all. Of course, even Halo forgot to let you cancel the Context Sensitive Button's making you slowly clamber into nearby vehicles.
 * Most of your attacks in Viewtiful Joe would cancel each other, noticeably so in slow-motion. It was very much Difficult but Awesome; it made an already steep learning curve even nastier by making you interrupt half of your own attacks, but once mastered it gave a great amount of control over shifting attacks very quickly.
 * An unusual genre for this, Metal Gear Solid has the 'Quick Reload' technique. Normally when you exhaust a clip you have to reload normally which actually does take about 2 seconds; in a boss fight this is often about 1.9 more seconds than you have to spare. By unequipping and reequipping a weapon, it automatically reloads for you. On top of that, the manuals actually tell you about this technique!
 * From Tales of Symphonia, we have Spell Cancelling, which allows five out of the nine available characters to more or less break the game.
 * Later on someone discovered Auto Spell Cancelling, allowing Raine, to join in the sadism: Like this.
 * This is sometimes used to train faster in Runescape; an example is eating while fishing.
 * The Gundam vs. Series had an interesting evolution for this. In Gundam vs. Gundam, the Freedom had it as a unique special move (SEED Mode), which made it a Game Breaker. Gundam vs. Gundam Next made this part of the game engine under the name Next Dash, executed by double-tapping the Jump/Boost button. Gundam Extreme Vs. renamed it Extreme Action and made performable by double-tapping either Jump or any direction, making it a literal dash-cancel. In the cases of Next and Extreme, the move costs about 1/5 of your Boost Gauge.
 * In Metroidvania Castlevania games there are a few methods of canceling, the most universal being the back dash and landing. Many of the Castlevania: Chronicles of Sorrow souls and Portrait of Ruin subweapons are AMAZING when canceled (Killer Clown, Dart), key for Boss Rushes. Dawn of Sorrow also has the Succubus cancel, which, when combined with a special dagger that temporarily moves you forward, lets you teleport though walls.
 * This started in Symphony of the Night, where your backdash move had NO LAG. The designers wised up and added lag or animation time to it in subsequent games, but often a backdash still gives you a net gain, and landing still lag cancels in every game. One exception to this was Circle of the Moon; the gun card combo in particular didn't fire unless you were on the ground already.
 * God Hand is basically built around canceling out of your moves by dodging.
 * There are quite a few cancels in the Devil May Cry series. Moving just a fraction while using the shotgun to cancel the reload, and multiple ways to Grenade Cancel, to fire the normally slow grenade launcher gun at a really fast clip. In 3 and onwards, cancelling short hops and rolls into the guarding animation of the Royal Guard style is a very effective defensive tactic and makes the Difficult part of its Difficult but Awesome slightly less so. You can also cancel the after-shot lag of the Spiral rifle and Kalina Ann rocket launcher by either switching to Ebony&Ivory immediately afterwards or timing a use of Royal Guard properly.
 * There's also jump cancelling, where you can cancel a jump with a basic attack, and cancel a successful basic attack with another jump. Done right, you can just hover at an enemy's head batting away.
 * GunZ, Cancel based techs have dominated the game after their discovery.
 * Most speed runners can tell you that Mega Man games that include dash commands are notorious for Dash Canceling, where you can maintain the fastest part of the dash command way longer than the dev team intended you to by constantly performing some other button press.
 * In Mega Man X, you can cancel Zero's Z-Saber with a dash, and a dash with the saber. With fast Button Mashing, this becomes a Game Breaker because not only can you swing the saber much faster, but most bosses are designed only to activate their Mercy Invincibility on the third swing of Zero's three-hit combo. By never using that third swing, bosses can be killed in mere seconds.
 * In some Tetris games (such as the TGM series), there is a short delay between when you lock a piece into place and when the next piece appears. One Tetris fangame, DTET, features this, but allows you to cancel it and immediately spawn the next piece by performing an input.
 * Gorf, like many other shmups from the early 80's and late 70's, only lets you fire One Bullet At a Time, so if you fire a shot and miss, you have to wait a bit before firing the next shot. However, Gorf allows you to cancel your current shot and immediately fire your next one, simply by firing when you have a shot on the screen.
 * Bangai-O Spirits has EX canceling, performed by hitting a regular attack button while charing an EX attack. Different from most examples here in that it prevents an attack instead of interrupting it, but it's useful if you start up an EX attack but change your mind before you fire it.
 * The entire gameplay premise of the four Virtual On games are built upon knowing when to cancel moves. The most well-known and important move accepted by the players community is "jump-cancelling", which can do anything from reducing time spent frozen after landing from a full jump (and thus being a very tantalizing target) to avoiding melee attacks, and in later games, set up for other forms of attacks.
 * The most notable advantage of Lord of Arcana's 2H Sword weapon type is that the second and third swings of its combo can be cancelled into a block, allowing for much safer attacks.
 * Asura's Wrath has Jump canceling to follow up with a launcher attack to do an air combo and a homing cancel that's used to home in onto locked on opponents after an air combo knocks them out of the sky, allowing for more follow ups and higher scores.
 * Monster Hunter has some lengthy animations that lock your character in place, but some can be canceled by blocking, dodging, or re-sheathing your weapon. The Great Sword has particularly excruciating animations where a hunter brings the weapon back to a ready position after a big attack, making this technique an absolute necessity.
 * Dragons Dogma has an actual cancel ability called Reset. It's available to Striders and cancels all animations except hitstun. It's upgraded version, Instant Reset, allows you to cancel out of hitstun.