b-roll is alternate footage recorded in addition to the principle action of a given scene. Typically b-roll is used to show audience reaction, or add descriptive visuals to otherwise dry dialog.

More importantly for editors, b-roll is used to disguise jump cuts in edited video sequences.

The term B-roll stems from the days of linear video editing when there were a principle deck held the A-roll video and a secondary deck included the B-roll cutaway content.