|The user ensnares the target with thin, gooey silk so it can't flee from battle.|
Spider Web prevents the target from switching out or fleeing (including via Teleport). It bypasses accuracy checks to always hit, unless the target is in the semi-invulnerable turn of a move such as Dig or Fly. Spider Web's effect only applies as long as the Pokémon that used it remains in battle.
Pokémon affected by Spider Web can escape if the Pokémon has the Ability Run Away, is holding a Smoke Ball or uses U-turn.
If a Pokémon traps a target with Spider Web and then switches with Baton Pass the target will no longer be trapped. Pokémon affected by Spider Web can switch out with Volt Switch. Also, Dragon Tail and Circle Throw will force the affected Pokémon to switch out.