Tech-chasing is the act of following or predicting an opponent's tech in order to attack him before he can respond. Because a character's tech animations have small windows of vulnerability before a character can shield, sidestep, dodge, or attack, it is possible to read the direction of a player's tech and punish the lag with an attack, jump-canceled grab, or projectile.
Some characters are able to incorporate tech-chasing into a chain grab sequence. A classic example is Captain Falcon's up throw against fast-fallers. After he throws, Captain Falcon can gain another grab by successfully tech-chasing his enemy.