Detect protects the user from all effects of moves during the turn it is used, including damage. Detect is functionally identical to Protect.
Detect fails if the user goes last (usually a result of the opponent using an item or switching). Successfully using Detect, Protect, Endure, Wide Guard, Quick Guard, or Spiky Shield divides the success rate for all six by 3, up to a minimum of [1/3]^6, or 1/729 (~0.1% chance of success). Using a different move or failing to use a protection move resets the success rate. Being hit by Feint or Phantom Force will lift the effects of Detect for the rest of the turn.
Detect cannot block damage from status conditions or weather. It also cannot block the following moves: