drop in vs drop by

drop in and drop by both are verbs.

Word	Noun	Adjective	Verb	Adverb
drop in	No	No	Yes	No
drop by	No	No	Yes	No

As verbs, drop in and drop by are synonyms defined as:

Other synonyms of drop in include come by.

drop in (verb)	drop by (verb)
visit informally and spontaneously	visit informally and spontaneously