@JeremyECrawford My PC uses the invisibility spell, does he auto hide or do I still need to take the hide action to not be targeted?
— Mr. Noname (@fritomuncher) December 28, 2015
The invisibility spell doesn't automatically hide you; you still make noise. #DnD https://t.co/Lalz7DZIGR
— Jeremy Crawford (@JeremyECrawford) January 5, 2016
Some creatures have a great sense of smell so may detect you that way.