As nouns the difference between bystander and onlookers
is that bystander is a person who, although present at some event, does not take part in it; an observer or spectator while onlookers is plural of lang=en.
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