Stacks

Stacks brings smart contracts and applications to Bitcoin. Bitcoin's base layer is deliberately limited in what it can express, so Stacks operates as a separate layer that anchors to Bitcoin and lets developers build applications whose final settlement depends on Bitcoin's security.

Applications on Stacks are written in Clarity, a language designed to be decidable, meaning what a contract will do can be determined by reading it without executing it. Clarity contracts can also read Bitcoin state directly, so an application can react to Bitcoin transactions without an intermediary reporting them.

Proof of transfer

The consensus mechanism is proof of transfer. Miners commit bitcoin to compete for the right to produce Stacks blocks, and that committed bitcoin is distributed to STX holders who participate in a process called stacking. This means Stacks miners spend bitcoin rather than electricity, and the reward for stackers is paid in bitcoin rather than in the network's own token.

Stacking is the network's distinctive feature: locking STX for a period earns bitcoin yield sourced from miner commitments, rather than newly issued tokens. The Nakamoto upgrade, delivered in 2024, changed block production so Stacks transactions confirm much faster while still anchoring to Bitcoin for finality, and introduced sBTC, a bitcoin-backed asset usable in Stacks applications.

Supply

STX has no listed maximum supply in current data, with total and circulating supply both at roughly 1.86 billion tokens. Emission continues under the protocol's schedule.

Stacks is the largest project in the Bitcoin layer category, an area that has attracted renewed attention as interest in making bitcoin productive has grown.