Stacks (STX)

What Stacks is

Stacks is a blockchain that anchors itself to Bitcoin and lets Bitcoin holders earn BTC without selling it. STX is its native asset. The consensus mechanism, Proof of Transfer, is described in Stacks's documentation by direct analogy: "Like how Bitcoin PoW miners spend electricity and are rewarded in BTC, Stacks PoX miners spend (already mined) BTC and are rewarded in STX" (source: Stacks documentation, Proof of Transfer, read September 2026).

The BTC those miners spend does not disappear. Stacks's documentation states that "Spent BTC (from miners) are sent to STX holders" who have locked their STX, a process the network calls Stacking. So the chain converts mining competition into a Bitcoin-denominated payment stream for STX holders, rather than burning energy or paying an issuance subsidy.

For where to buy Stacks from your country or state, see the availability tables on this site and the venues listed at Exchanges.

How it works

Miners bid for the right to produce blocks by sending Bitcoin transactions. Each bid embeds verifiable random function state, which makes the winner "deterministic but unpredictable at each Bitcoin block," so nobody can compute the outcome in advance but everybody can verify it afterwards. The cost of competing is denominated in BTC rather than in electricity.

Stackers lock STX to receive the miners' BTC. Payouts are proportional to an individual's lockup relative to total lockup, and the documentation notes that locked STX remains in the holder's own account and unlocks automatically rather than being transferred to a custodial contract.

Time is organized by Bitcoin. A reward cycle spans 2,100 Bitcoin blocks: a 2,000-block reward phase followed by a 100-block prepare phase, with the anchor block being the first Stacks block confirmed during the prepare phase. Because the cycle is measured in Bitcoin blocks, the schedule inherits Bitcoin's timing rather than setting its own.

The Nakamoto upgrade, which hard-forked the network in the fourth quarter of 2024, changed how blocks are produced. Before it, transaction confirmation took "tens of minutes"; after it, confirmations take "on the order of seconds." Miners now "produce many Stacks blocks per Bitcoin block instead of one," and a miner's tenure spans the duration of one Bitcoin block.

Nakamoto also gave Stackers a consensus role rather than only a reward. The documentation states that "Stackers will need to collectively validate, store, sign, and propagate each Nakamoto Stacks block," which means a miner cannot unilaterally create a fork. The threshold is explicit: "This blockchain will only fork if 70% of Stackers approve the fork." The documentation describes the result as "100% Bitcoin finality," where once a transaction is confirmed, "reversing it is at least as hard as reversing a Bitcoin transaction." A chain reorganization on Stacks therefore requires a reorganization of Bitcoin itself.

sBTC is the asset that makes this useful. Stacks's documentation describes it as "a decentralized, trust-minimized two-way Bitcoin peg between Bitcoin and the Stacks blockchain," implemented as a SIP-010 fungible token, letting Bitcoin holders represent BTC on Stacks "without relying on a single trusted entity."

Supply and tokenomics

Stacks's documentation states three uses for STX: mining incentives paid through a new block subsidy, economic security for the Bitcoin peg, and gas fees. It denominates STX in micro-STX, with 1,000,000 micro-STX to one STX, stored as 8-byte integers. It does not publish a total supply cap or an emission schedule on the pages read for this entry, so no supply figure is stated here.

Dual Stacking is the current reward structure, and its parameters are specific. All participants receive a baseline BTC-denominated reward on the sBTC they enroll. Stacking STX alongside that sBTC raises the yield by up to a factor of ten, and deploying the sBTC into defi applies a further multiplier of up to ten. The scaling follows "a square-root curve, meaning the first stacked STX has the greatest impact," measured against a reference threshold set at the 95th percentile of BTC-weighted STX/BTC ratios. STX committed this way continues to earn standard Stacking rewards at the same time.

The square-root curve is the detail that changes how a holder should read the maximum multiplier. Because the first STX stacked contributes most, the ten-times figure is the ceiling of a curve with steeply diminishing returns, not a rate that scales linearly with the size of the position.

History

Stacks's architecture answers a question Bitcoin does not answer for itself: how to build programmable applications whose security derives from Bitcoin without changing Bitcoin. Proof of Transfer routes economic cost through the Bitcoin chain, and the reward cycle is measured in Bitcoin blocks, so the two chains stay coupled by construction rather than by a bridge.

Nakamoto in late 2024 was the upgrade that made the design practical. Decoupling block production from miner elections allowed fast blocks, and giving Stackers signing authority over each block converted them from passive reward recipients into the parties that enforce the chain's history. The 70% approval requirement for a fork is what turns Bitcoin anchoring into an actual reorganization guarantee rather than a timestamping convenience.

sBTC followed, giving Bitcoin holders an on-chain representation of BTC on Stacks without a single custodian, and Dual Stacking then paid them for enrolling it.

Risks and what to watch

Stacker concentration is the security parameter that matters most after Nakamoto. Because a fork requires 70% of Stackers to approve it, and because Stackers sign every block, who holds locked STX now determines liveness as well as rewards.

Locking STX to Stack means the position is committed for the cycle. Stacking through a pool or an exchange adds that operator's risk on top of the protocol's, and availability of such products differs by jurisdiction.

sBTC is a peg, and every peg has a failure mode. Trust-minimized is not trustless: the guarantees depend on the signer set and the contract logic behind the two-way peg, and a holder of sBTC holds a claim rather than BTC itself.

Miner economics depend on the BTC price of block production. If the STX rewarded is worth less than the BTC spent, mining participation falls, and with it the BTC flowing to Stackers.

Clarity, the contract language used on Stacks, has a smaller ecosystem and a smaller pool of auditors than the EVM's, which is a real smart contract audit constraint.

Frequently asked questions

What is Proof of Transfer?

Stacks's consensus mechanism. Miners spend already-mined Bitcoin to compete for the right to produce Stacks blocks and are rewarded in STX. The Bitcoin they spend is paid to STX holders who have locked their tokens.

How do Stacks holders earn Bitcoin?

By Stacking, which means locking STX. Miners' spent BTC is distributed to Stackers in proportion to each holder's lockup relative to the total. Locked STX stays in the holder's own account and unlocks automatically.

How long is a Stacks reward cycle?

2,100 Bitcoin blocks, made up of a 2,000-block reward phase and a 100-block prepare phase. Because the cycle is counted in Bitcoin blocks, it follows Bitcoin's timing.

What did the Nakamoto upgrade change?

It hard-forked the network in the fourth quarter of 2024, cutting confirmation from tens of minutes to seconds, letting miners produce many Stacks blocks per Bitcoin block, and giving Stackers signing authority over every block. A fork now requires 70% of Stackers to approve it.

Where can you buy Stacks?

Availability depends on your country or US state. See where to buy Stacks for the exchanges serving your jurisdiction, and Exchanges to compare fees, kyc requirements and payment methods.