8mm was a standard film format, so named because of its 8-millimetre width. As such it was the smallest of the major film sizes, and never used by the production staff to record Doctor Who. However, because it was cheaper to buy and develop than 16mm or 35mm, it became the medium of choice for "home movies". Over the years, several people, sometimes only vaguely connected with the production of Doctor Who, would take 8mm home movies of the recording of Doctor Who — particularly location filming. For several missing episodes, 8mm recordings of filming give vital insights into what the production may have looked like.
Amongst the serials whose action was captured in some way by 8mm recordings are: The Reign of Terror, Galaxy 4, The Myth Makers, The Savages, The Smugglers, The Tenth Planet, The Power of the Daleks, The Macra Terror, The Evil of the Daleks, The Abominable Snowmen, Fury from the Deep, The Dæmons, and Shada. Undoubtedly the most famous example of an 8mm recording was the amateur telerecording of the first regeneration scene as the end of The Tenth Planet. Because of its singular importance, the British Broadcasting Corporation has frequently allowed the rebroadcast of these surviving images, despite their inferior quality. Generally, though, most 8mm recordings have not been used by the BBC in any significant way.