all-night vs overnight

all-night and overnight both are adjectives.

Word	Noun	Adjective	Verb	Adverb
all-night	No	Yes	No	No
overnight	No	Yes	No	Yes

As adjectives, all-night and overnight are synonyms defined as:

all-night and overnight: lasting, open, or operating through the whole night

Other synonyms of all-night include nightlong.

all-night (adjective)	overnight (adjective)
lasting, open, or operating through the whole night	lasting, open, or operating through the whole night

all-night (adverb)	overnight (adverb)
	during or for the length of one night
	happening in a short time or with great speed