Twitter chief executive Jack Dorsey has sold a digital version of his first tweet for more than $US2.9 million ($3.8 million) more than two weeks after he announced a digital auction for the post.

The tweet from March 2006, which says “just setting up my twttr,” was bought by Bridge Oracle CEO Sina Estavi, according to Valuables by Cent, the digital platform where the digital auction for the tweet was held.

The 15-year old post was sold as a non-fungible token, or NFT – a digital certificate of authenticity that confirms an item is real and one of a kind by recording the details on a blockchain digital ledger.

15 years ago today Jack Dorsey sent the world's first tweet.#HappyBirthdayTwitter #Twitter15 pic.twitter.com/4aWmAU2wlt

— MIT CSAIL (@MIT_CSAIL) March 21, 2021

Dorsey tweeted earlier this month that the proceeds would be converted to bitcoin and given to the non-profit GiveDirectly’s Africa Response.

The charity has been raising money to support African families who were financially affected by the coronavirus pandemic.

According to Valuables, 95 per cent of of the proceeds from the sale price go to the tweet’s creator and five per cent of it goes to the platform.

Dorsey tweeted the bitcoin receipt on Monday afternoon and said the funds were sent to the charity.

NFTs have recently swept the online collecting world.

A digital artwork by the artist Beeple sold for $US69.4 million in an online auction by a British auction house earlier this month, with an NFT as a guarantee of its authenticity.