Tumblr, the teen-friendly social network which once dominated online youth culture, will be sold at a staggering 99pc writedown after six long years of failure to turn a profit.

The popular blogging service was bought by Yahoo in 2013 for $1.1bn (£910m), one of a string of high-profile acquisitions intended to rejuvenate the ageing web titan's fortunes.

But on Monday, Yahoo's parent company Verizon finally admitted defeat in its long quest to monetise Tumblr, agreeing to sell the service for less than 2pc of what it originally cost.

The US telecoms giant, which absorbed Yahoo in 2017 for $4.5bn, said it would sell Tumblr to Automattic, owner of the rival blogging service Wordpress. While it did not give a price, the US news website Axios put the transaction at "well below" $20m and possibly as low as $3m – barely more than the cost of a McDonald's franchise.

Either figure would represent a remarkable writedown for a social network once considered the centre of online youth culture, used by celebrities including Taylor Swift, Lady Gaga and Zooey Deschanel.

It comes over Tumblr lost almost one third of its traffic following a controversial ban on pornography and erotica, which aimed to clean up the site's image with advertisers and phone companies but which was deeply unpopular with many users.