informant vs witnesser

informant and witnesser both are nouns.

Word	Noun	Adjective	Verb	Adverb
informant	Yes	No	No	No
witnesser	Yes	No	No	No

As nouns, informant and witnesser are synonyms defined as:

informant and witnesser: someone who sees an event and reports what happened

Other synonyms of informant include witness.

informant (noun)	witnesser (noun)
a person who supplies information	someone who sees an event and reports what happened
someone who sees an event and reports what happened