Twitter has unveiled plans to delete accounts which have been inactive for more than six months.
Users have until 11 December to prevent dormant accounts from being affected by the huge “clean-up”.
Coveted Twitter handles are set to become available as a result of the clear out – but there are fears that accounts belonging to people who have died could end up being erased too.
The social network says it is exploring ways to memoralise such accounts, ensuring that messages and photographs are preserved for family and friends. Facebook already offers a similar feature.
Twitter says the clear out is necessary because the owners of dormant accounts have been unable to agree to the company’s new privacy policies.
The company is also considering whether to remove the accounts of users who do log in but “don’t do anything”.
Dan Hett, whose brother Martyn was killed in the Manchester Arena terror attack, is among those concerned about Twitter’s policy.
Mr Hett tweeted: “Twitter and social accounts can and do become vital when someone checks out, especially when it’s unexpected like in the case of @martynhett.
“He didn’t know he was writing an important digital legacy in his throwaway tweets, but now we have it we mustn’t lose it.
“There are archival services that will scrape all the content, but this isn’t enough.
“The idea that one day you could tag @martynhett and have nothing appear, or worse someone else who’s taken the handle, is not the one.”