Q: Dear Sage,
Can detect magic be used to identify magical traps? Would nondetection block this?
A: Detect magic locates magical traps, but it can’t identify anything more than the location and strength of the aura revealed (and, with a successful Spellcraft check, the school of magic involved). Thus, technically the spell doesn’t actually reveal the fact that the magical trap is, in fact, a trap.
Nondetection wards a trapped object from detect magic (requiring a caster level check to pierce the nondetection). An even better option is Nystul’s magic aura, which can conceal a magic trap’s aura (or change it to appear as that of another spell of your choice).
About the Author
The Sage is a mammal classified in the bear family, Ursidae, native to central and southern China. Debate continues as to whether he is truly a bear or more related to the raccoon rather than the bear, or perhaps in a family of his own. When not eating bamboo and answering rules questions, he works under the nom de plume of Andy Collins as an RPG developer in Wizards of the Coast R&D, where his development credits include Complete Mage, Dragon Magic, and the Player's Handbook v.3.5. He can be easily recognized by his large, distinctive black patches around the eyes, ears and on his rotund body.