Did you know?

Click any word in a definition or example to find the entry for that word

bit rot

noun [uncountable]

when electronic information is lost because the software or devices needed to read it are no longer available

'Concern is popping up in the digital media world over the future of online documents like pictures, videos and more. … Bit rot is concerning because programs needed to view documents will eventually become outdated and replaced with newer technology.'

KIMT News 3 25th February 2015

The concept now seems ludicrous, but there was a time when, working as a lexicographer for a mainstream publisher, I routinely wrote dictionary entries on paper and was instructed to take photocopied bundles of my work home as a precautionary measure in case the building I worked in unexpectedly caught fire. The image of someone storing important data on piles of paper in their spare room seems laughable in today's world, but in relation to a phenomenon newly described as bit rot, it may not be such a crazy idea after all.

we digital immigrants have been battling bit rot even before we had a name for it, trying to stay ahead of the game by transferring any data we really care about between different physical formats
whilst we still have the chance

The expression bit rot refers to a process in which electronic data becomes useless because the mechanisms required to access it are no longer available. In practice this happens in one of two ways, and if you're as old as I am, you're likely to be familiar with the first. In the mid 1980s it looked like so-called floppy disks were here to stay, so it was a bit of a shock some years later when the 5¼ inch ones suddenly shrank to 3½ inches, and then eventually disappeared altogether, rendering any data stored on them unreadable without a computer featuring the relevant disk drive. This is a classic example of how, as technology advances, we digital immigrants have been battling bit rot even before we had a name for it, trying to stay ahead of the game by transferring any data we really care about between different physical formats whilst we still have the chance.

The second cause of bit rot is a little more subtle, and relates to the software required to read particular file formats. If this software becomes obsolete and the file format no longer supported, then any documents using those formats would be unreadable once the old software no longer runs on newer computers. The bottom line here then, obvious but significant, is that computer files are worthless without the software to open them.

The phenomenon of bit rot was recently brought into the public eye by American internet pioneer Vint Cerf, who claims that people are unwittingly throwing their data into what could become 'an information black hole'. Cerf points out that we digitize things – photos, music, documents, etc – in order to preserve them, but that, paradoxically, those digital versions might be more fragile than the original, physical forms because the programs needed to view them could become defunct. Ironically, he has been quoted as saying "if there are any photos you really care about, print them out".

Background – bit rot

The concept of bit rot is nothing new, an early example being VHS video cassettes, gradually superseded by other technologies and so rendered useless when video players were eventually withdrawn from circulation. This is sad for anyone, myself included, with family memories stored on these kind of tapes. Some experts feel however that bit rot may be less of a problem in the current era of digital files, which are arguably much easier to recover than something physical that needs a specific machine.

The expression is made up of bit in its computational sense of 'a unit of information' (compare also the recent bitcoin) and rot as in 'the process of decaying', possibly by analogy with other new expressions such as link rot (a situation where links on a website don't work).

by Kerry Maxwell, author of Brave New Words

Last week …

Read last week's BuzzWord. Brinner.

This article was first published on 27th May 2015.

Open Dictionary


a form of location that involves the underwater detonation of a bomb which causes sound waves that are picked up by ships

add a word


A must for anyone with an interest in the changing face of language. The Macmillan Dictionary blog explores English as it is spoken around the world today.

global English and language change from our blog