besides vs as well

besides and as well both are adverbs.

Word	Noun	Adjective	Verb	Adverb
besides	No	No	No	Yes
as well	No	No	No	Yes

As adverbs, besides and as well are synonyms defined as:

Other synonyms of besides include also, likewise, too.

besides (adverb)	as well (adverb)
making an additional point; anyway	in addition
in addition