up to now vs thus far

up to now and thus far both are adverbs.

Word	Noun	Adjective	Verb	Adverb
up to now	No	No	No	Yes
thus far	No	No	No	Yes

As adverbs, up to now and thus far are synonyms defined as:

up to now and thus far: used in negative statement to describe a situation that has existed up to this point or up to the present time

Other synonyms of up to now include as yet, heretofore, hitherto, so far, til now, until now, yet.

up to now (adverb)	thus far (adverb)
used in negative statement to describe a situation that has existed up to this point or up to the present time	used in negative statement to describe a situation that has existed up to this point or up to the present time
prior to the present time