instantly vs immediately

instantly and immediately both are adverbs.

Word	Noun	Adjective	Verb	Adverb
instantly	No	No	No	Yes
immediately	No	No	No	Yes

As adverbs, instantly and immediately are synonyms defined as:

instantly and immediately: without delay or hesitation; with no time intervening

Other synonyms of instantly include at once, directly, forthwith, like a shot, now, right away, straight off, straightaway.

instantly (adverb)	immediately (adverb)
without delay or hesitation; with no time intervening	without delay or hesitation; with no time intervening
without any delay	near or close by
	bearing an immediate relation