MySpace, one of the first online social networks, has apologised after a server migration caused a huge loss of data.
A message on its website says that "any photos, videos and audio files" uploaded more than three years ago may no longer be available.
There had been complaints going back several months that links to music were no longer working.
The platform has waned in popularity since it was founded in 2003 but in its prime it attracted millions of users.
In 2006 it was the most visited site in the US - beating Google.
It was a popular platform for sharing new music, and has been credited with helping to launch the careers of artists including the Arctic Monkeys and Kate Nash.
"As a result of a server migration project, any photos, videos, and audio files you uploaded more than three years ago may no longer be available on or from MySpace," the firm said in a statement.
"We apologize for the inconvenience."
It also included the email address of its data protection officer Dr Jana Jentzsch.
The BBC has contacted Dr Jentzsch for comment.
Andy Baio, who helped build the Kickstarter crowd-funding site, tweeted that the loss could amount to some 50 million tracks by 14 million artists over that period.
He also questioned whether the loss was accidental.
I'm deeply skeptical this was an accident. Flagrant incompetence may be bad PR, but it still sounds better than "we can't be bothered with the effort and cost of migrating and hosting 50 million old MP3s."— Andy Baio (@waxpancake) March 18, 2019
"Flagrant incompetence may be bad PR, but it still sounds better than 'we can't be bothered with the effort and cost of migrating and hosting 50 million old MP3s'." he wrote.
MySpace was bought by NewsCorp in 2005 for $580m (£437m). It was sold in 2011 for $35m to ad targeting firm Specific Media.
While it is no longer a major player in the social media field, some people who used it in its prime still used it as an archive.
Welp, there goes my high school experience— ℹ️❤️🖥 aka Compy-chan (@ilovecomputers) March 18, 2019