Outgoing US leader Barack Obama promised followers that tweets from his eight years in office will be preserved.

It means those who follow the official account will find themselves following an extra one.

That's because Obama's tweets will be transferred to @Potus44.

"Potus" stands for President of the United States.

Obama's White House team developed the strategy for the handover several months ago.

It seems clear there was a worry that tweets could otherwise be deleted.

"We are working to ensure these materials continue to be accessible on the platforms where they were created," an official blog states.

"Moving forward, the president and first lady can be followed on familiar handles: @BarackObama and @MichelleObama."

The Democratic administration approached Twitter with a plan to make the process as smooth as possible.

Twitter then acted as a go-between for the Obama and Trump camps.

"We are in constant contact with their social media team - this was their idea on how to do it," a Twitter spokesman, based in Washington DC, tells Newsbeat.

"On the 20th all the @Potus content will turn into @Potus44 - the description will change, the photo will change, and it will say: this is the account of the Obama administration.

"When we switch the handle for @Potus44, we'll auto-reserve the @Potus handle. We reserve it so they [Trump's social team] can take it.

"It will then be associated with the email they have given us. It becomes theirs. All the followers we add back onto the account.

"So [if you follow @Potus now] you'll go up one in your follows."

The spokesman said it was the first time such a detailed strategy had been necessary.

When Obama took office in 2008, official Twitter accounts on this scale didn't yet exist.

The same handover rules will apply to Joe Biden's @VP account and to @Flotus.

Michelle Obama's tweets as first lady will be preserved as @Flotus44 and Melania Trump will inherit her followers as @Flotus.

There's a campaign by anti-Trump groups to "mass unfollow" these accounts once the switch has happened.

But the handover strategy means there's zero risk of anything being erased.

"That was the goal," says the Twitter spokesman.

It was a different story in the UK when David Cameron's team took over the @Number10gov Twitter handle after Gordon Brown's exit in 2010.

All of the Brown-era tweets vanished overnight.

The new White House team will take over the official White House YouTube, Facebook, Snapchat, Instagram, Tumblr and Flickr accounts.

Trump's transition team have said the new president plans to keep tweeting from his @realdonaldtrump account as well as using @Potus for official business.

That means it's unlikely his well-documented late-night Twitter spats will be firing off from @Potus any time soon.