Male and female barn swallows are similar in appearance, but males tend to be more vibrantly colored and have longer outer tail-streamers.
Barn swallows are small, distinctive, passerine birds. They range in size from 14.6 to 19.9 centimeters long (5.7-7.8 inches), with a wingspan of 31.8 to 34.3 centimeters (12.5-13.5 inches). They weigh between 17 and 20 grams (0.6-0.7 ounces).
Barn swallows are metallic blue-black across the back and pale beige on the stomach. The barn swallow has light brown on its throat and forehead and has a long, deeply-forked tail.
Males and females are similar in appearance, though females tend to be less vibrantly colored and have shorter outer tail-streamers.