in short vs briefly

in short and briefly both are adverbs.

Word	Noun	Adjective	Verb	Adverb
in short	No	No	No	Yes
briefly	No	No	No	Yes

As adverbs, in short and briefly are synonyms defined as:

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

in short (adverb)	briefly (adverb)
in a concise manner; in a few words	for a short time
	in a concise manner; in a few words