Fifteen years ago Jack Dorsey typed out a banal message -- "just setting up my twttr" -- which became the first ever tweet, launching a global platform that has become a controversial and dominant force in civil society.

The short tweet on March 21, 2006 by the Twitter CEO is now being sold at auction, with bidding reaching $2.5 million.

It has been a long, strange journey for the social network, which in January deleted former president Donald Trump's account after he was blamed for inciting the violent insurrection on the US Capitol in January by extremist supporters seeking to overturn his election loss.

Twitter is a dominant and controversial force in civil society
Twitter is a dominant and controversial force in civil society AFP / Olivier DOULIERY

The banning of a head of state from the platform was both welcomed and denounced in a sign of the thin line Twitter and other social media networks often try to walk between neutrality, freedom of expression, and moderation and prevention of abuse.

Bidding on Dorsey's tweet ends later Sunday. He has said he will donate the funds to charity.

Dorsey's tweet will be sold as an NFT, or a non-fungible token.

NFTs use the same blockchain technology behind cryptocurrencies to turn anything from art to sports trading cards into virtual collector's items that cannot be duplicated.