Stacks brings smart contracts and applications to Bitcoin. The Stacks ecosystem is a collection of independent entities, developers, and community members working to build a user-owned internet on Bitcoin. The Stacks blockchain extends the design of Bitcoin to enable secure apps and predictable Clarity smart contracts without modifying Bitcoin itself, opening innovation on the network for the first time. The Stacks cryptocurrency (STX) is used as fuel for networking activity and contract execution and can be locked by STX holders via ‘Stacking’ to earn Bitcoin (BTC) rewards for supporting blockchain consensus. In 2019, Stacks, formerly Blockstack, was the first cryptocurrency in the United States to qualify for a Reg A+ token offering.