As nouns the difference between passerby and bystander
is that passerby is alternative spelling of passer-by while bystander is a person who, although present at some event, does not take part in it; an observer or spectator.
passerby
English
Noun
(passersby)
Alternative spelling of passer-by .
bystander
English
Noun
(
en noun)
a person who, although present at some event, does not take part in it; an observer or spectator
See also
* rubberneck