Block

Jack Dorsey, also the cofounder of Twitter, launched the payments giant in 2009 as Square with Jim McKelvey but rebranded the company to Block in 2021, partly as a nod to the growing importance of blockchain.

Block is a major supporter of the Bitcoin ecosystem and has spun out an open-source development project called Spiral and began developing its own mining hardware, the Proto Rig. Block is also one of a number of public companies to hold Bitcoin on its balance sheet. The company's flagship payments app, Cash App, helped generate around a third of its $6 billion in overall revenue in the first quarter of 2026.