thumb|right|B-roll video of computer [[server racks|thumbtime=13:53]]
In film and television production, B-roll, B roll, B-reel or B reel is supplemental or alternative footage intercut with the main shot. The term A-roll, referring to main footage, has fallen out of use to some degree.
B-roll may be shot by smaller second unit crews, since there is no need for sound. In film, smaller MOS cameras, lacking sound circuitry, may be used for greater portability and ease of setup. In a docudrama project, B-roll may refer to dramatic re-enactment scenes staged by the producer and performed by actors, to be used as cutaway shots.
There are many different types of B-roll, including: insert shots, FX shots, establishing shots, stock footage, and pickup shots.
B-roll footage may be added to or drawn from a stock footage library.
Until the mid-1970s, news teams shot both main A-roll and secondary B-roll footage on 16 mm film. Sound was integrated onto the film by way of a magnetic stripe at the edge of the film. The A-roll and B-roll scenes, shot at 24 frames per second, were converted to the television frame rate of 30 fps using a telecine system consisting of two film projectors, one showing the main A-roll footage and the other showing the B-roll. The sound from the A-roll footage was used, or sound from narration or voiceover, while MOS images from the B-roll were intercut as desired.