Arcane Sight

For the duration, your eyes glow blue and you can see magic within 60 feet of yourself.  You see a faint aura around any creature or object within range that bears magic, and you learn its school of magic, if any. 

As an action, you can focus on a creature you can see within range to determine whether or not it is a spellcaster.  If it is, you also learn the level of the highest-level spell it can currently cast that isn't from an item. 

You can also use your action to deactivate the spell, to reactivate it after you've deactivated it in this way, or to end it early.  While deactivated, the spell has no effect, but can still be detected normally, and its duration continues to expire. 

The spell can penetrate most barriers, but it is blocked by 1 foot of stone, 1 inch of common metal, a thin sheet of lead, or 3 feet of wood or dirt. 

At Higher Levels.  When you cast this spell using a spell slot of 4th level or higher, it lasts longer: 20 minutes at 4th level, 30 minutes at 5th level, 1 hour at 6th level, 4 hours at 7th level, 8 hours at 8th level, and 24 hours at 9th level.