NFTs are digital files that serve as digital signatures to
certify who owns photos, videos and other online media. Dorsey, a known bitcoin
enthusiast, said the auction will end on March 21.
Payments company Square Inc, also led by Dorsey, invested
$170 million more in bitcoin last month, adding to the mainstream acceptance of
the digital currency that has been winning support from several big investors.
Dorsey's 15-year old tweet could attract bidders to pay a
high price for the digital memorabilia. The highest bid for the tweet stood at
$2.5 million as of 17:05 GMT on Tuesday.
The proceeds are being donated to GiveDirectly, a
fundraising project to give cash directly to families experiencing extreme
poverty in Africa.