How correct/common/proper is "pretty" as an adverb? It is hard for me to see, since it's my native dialect, but I say "pretty often" pretty often, and "fairly often" fairly rarely. Does "pretty" mark me as informal or uneducated or rustic?
The NOAD reports that pretty used as adverb is informal, and it means to a moderately high degree, fairly: he looked pretty fit for his age.
It's informal, but correct. The Cambridge dictionary lists an adverb form.
It's pretty common.