in brief vs shortly

in brief and shortly both are adverbs.

Word	Noun	Adjective	Verb	Adverb
in brief	No	No	No	Yes
shortly	No	No	No	Yes

As adverbs, in brief and shortly are synonyms defined as:

Other synonyms of in brief include briefly, concisely, in short.

in brief (adverb)	shortly (adverb)
in a concise manner; in a few words	in the near future
	for a short time
	in a curt, abrupt and discourteous manner
	at a short distance
	in a concise manner; in a few words