When a mage casts Detect Familiar, he is able to determine whether or not any animal within range serves as a familiar. This covers any animals linked to a mage via Find Familiar, as well as any variants of the spell. Detection is in the mage's line of sight along a 10-foot-wide path to the range limit.

The material component for this spell is a small amount of fur, scales, feathers, or skin from any creature serving or having served as a familiar.