A tech, officially referred to as a breakfall in Super Smash Bros. and an ukemi (受け身) in Super Smash Bros. Brawl and passive internally in Melee and Brawl, is an action performed when the character hits the ground, a wall, or a ceiling while tumbling or in hitstun. To tech, the user must press the shield button 20 frames or fewer before hitting the surface; after that, a player won't be able to tech for 40 frames. Additional button or control stick input can cause different types of techs.
The word "ukemi" refers to a rolling technique used in Japanese martial arts when taking an attack. The name has found its way into several (mostly fighting) games, such as Soul Calibur, to describe similar fall recovery moves.
The word "tech" is borrowed from the competitive communities of other fighting games and traces its origin back to technical bonuses awarded in Capcom games for performing special maneuvers to escape grab attacks and get much less damage and more recovery time.
 Types of techs
 Standard tech
A standing tech is a neutral, ground-based tech performed by pressing a shield button when a tumbling character comes in contact with the floor. The character will experience a brief period of invincibility, and will quickly bounce from the ground into a standing animation. The player will grab any items that he or she comes in contact with. This is the easiest tech to do, and is commonly done, even by casual players.
 Rolling tech
A rolling tech (or PassiveStandF and PassiveStandB, depending on the direction chosen), also called a techroll, is a ground-based tech performed by tilting the control stick left or right when teching. The character will bounce from the ground into a roll-like animation during which the character moves left or right while invincible. This can allow characters to roll away from their impact point to complicate tech chasing, but rolling against an edge will halt the roll's sideways movement.
 Wall tech
A wall tech (or PassiveWall) is a tech against a wall. To wall tech, the player must press a shield button 20 frames or fewer before hitting the wall while tumbling, reeling, or in hitstun. 20 frames after each press is a 40 frame downtime window where a wall tech cannot be done, so button mashing reduces the player's likelihood of teching. As with normal techs, the wall teching character experiences a few invincibility frames, and the tech absorbs the player's momentum.
 Ledge tech
A recovering character can use a form of wall tech to survive an edge-guarder. If the recovering character is hit with an attack very near to the ledge, he or she can smash DI towards the ledge and wall tech to absorb all the knockback of the enemy's attack. This is usually performed by pressing the shield button to wall tech before pressing the control stick to DI, because of the 20 frame window in which the player can input the tech before hitting the wall.
 Wall tech jump/Wall jump tech
If a jump input is active when a wall tech is performed (such as holding Up or pressing a jump button), then the teching character will wall jump. This is known as a wall tech jump. Though only certain characters can wall jump normally, every character can wall tech jump. A skilled player can survive a meteor smash (such as the Ice Climbers' forward aerial that often ends their chaingrabs) by wall tech jumping.
 Ceiling tech
A ceiling tech (or PassiveCeil) is a tech against a ceiling. To ceiling tech, the player must press the shield button 20 frames or fewer before hitting the ceiling, while in hitstun. 20 frames after each press is a 40 frame downtime window where a ceiling tech cannot be done, so mashing buttons reduces the player's likelihood of teching. As with normal techs, the ceiling teching character experiences a few invincibility frames, and the tech absorbs most of the momentum. It is shown on the Super Smash Bros. Brawl tutorial video on the Nintendo Channel that it can even save a character at 999%. There are few situations where there is a ceiling for a player to tech off of, but it can happen quite frequently in the caves of life in some stages.
 Changes between games
In Smash 64, only ground techs are available (standing and rolling), so on stages with many walls it can be difficult to avoid bouncing combos. Melee provides the addition of wall techs, wall jump techs, and ceiling techs, while Brawl removed the ability to ledge tech. However, as the new air dodge physics in Brawl allow airdodges to be used while tumbling, trying to tech too early will simply result in an airdodge. As a result teching requires more precision to perform.
 Tech use
Teching can be a lifesaver in many situations and is a good technique for beginners to learn and practice. Teching can also help the user escape from combos.
Occasionally after accumulating sufficient damage, one will experience a wall or ceiling rebound that will send the player plummeting off-stage. This can be prevented by applying a wall or ceiling tech, saving the player from a deadly ricochet. This is especially useful in Temple: a character in the large lower section of the stage can survive to very high damage and can immediately retaliate from otherwise-deadly blows. This unusual longevity is one reason Temple and similar stages are banned from tournaments.
The standing and rolling techs can be performed in many more situations and can allow a character to avoid continued assault after being knocked back. However, in many situations an opponent can predict a player's tech patterns and hit him or her again after knocking him or her down; knowingly setting up such situations is known as tech-chasing.
Edge-teching helps keep the character on the stage, or at least making it possible to recover to the stage.