Bitcoin is the largest and most well-known cryptocurrency network, but its intentionally limited scripting capabilities make it difficult to build the kinds of decentralized applications commonly found on programmable blockchains.
Stacks aims to change that.
Stacks is a Bitcoin Layer 2 designed to extend Bitcoin with smart contracts, decentralized applications, and decentralized finance (DeFi), without requiring changes to Bitcoin itself. The network settles on Bitcoin while providing developers with a separate execution environment for building more complex applications.
With the Nakamoto upgrade and the launch of sBTC, Stacks has taken a big step toward making Bitcoin a programmable asset that can be used across a broader on-chain economy.
In this article, we explore how Stacks works, the role of the STX token, and what makes its approach to Bitcoin unique.
What Is Stacks Exactly?
Stacks is a smart contract layer built on Bitcoin.
Its core proposition is relatively simple: instead of modifying Bitcoin to support more complex applications, Stacks adds an additional layer where developers can build smart contracts and decentralized applications while using Bitcoin as the underlying settlement layer.
Stacks blocks are cryptographically anchored to Bitcoin, allowing the network to leverage 100% of Bitcoin’s hash power to achieve Bitcoin finality on all Stacks transactions. Applications built on Stacks can also read and interact with Bitcoin state, opening the door to applications that use BTC as an asset while offering functionality that would be difficult to implement directly on Bitcoin.
The native asset of the network is STX. It is used throughout the Stacks economy, including for transaction fees and participation in the network's Proof of Transfer mechanism.
How Does Stacks Work?
At the center of Stacks is a consensus mechanism called Proof of Transfer (PoX).
Instead of using Proof-of-Stake, Stacks connects its block production process directly to Bitcoin.
Stacks miners commit BTC for the opportunity to produce Stacks blocks and receive newly issued STX and STX transaction fees. The BTC committed through this process is distributed to eligible STX holders participating in Staking. We will explain STX Staking more specifically later in this article.
This creates an economic link between the two networks:
Bitcoin → Proof of Transfer → Stacks → smart contracts and applications
PoX therefore reuses an existing Proof-of-Work asset, BTC, as part of the consensus process rather than creating a conventional Proof-of-Stake system.
Following the Nakamoto upgrade, STX stakers also play a consensus-critical role through the Stacks signers that validate blocks produced by Stacks miners.
Since PoX went live on mainnet in 2021, the Stacks protocol has distributed over 4,200 BTC to STX stakers.
The Nakamoto Upgrade
One of the most significant developments for Stacks was the Nakamoto upgrade, activated in October 2024.
Before Nakamoto, Stacks block production was closely tied to Bitcoin's roughly ten-minute block cadence. The upgrade introduced a significantly faster block-production architecture, bringing Stacks block times to around three seconds.
More importantly, Nakamoto strengthened the relationship between Stacks transactions and Bitcoin finality.
Once Stacks transactions reach Bitcoin finality, reversing them would require reorganizing Bitcoin itself. This allows Stacks to combine a faster application layer with the settlement assurances of the Bitcoin network.
For users, this means faster transactions without trading off Bitcoin’s unparalleled security. For developers, it provides an infrastructure optimized for high-performance DeFi protocols, including exchanges and lending markets.
What Is sBTC?
While Stacks provides the smart contract layer, another important challenge remains: how can native Bitcoin participate in those applications?
This is where sBTC comes in.
sBTC is a Bitcoin-backed asset on Stacks designed to maintain a 1:1 relationship with BTC. Users can deposit BTC and receive an equivalent amount of sBTC on Stacks, where it can interact with smart contracts.
This allows Bitcoin capital to remain native to the Bitcoin ecosystem while participating in applications such as:
- decentralized exchanges;
- lending and borrowing protocols;
- Bitcoin-backed financial products;
- payments;
- yield strategies; and
- other decentralized applications.
When users want to return to the Bitcoin network, sBTC can be redeemed back into BTC.
Rather than relying on a single centralized custodian to manage the underlying Bitcoin, the sBTC system uses a distributed signer model. Signers collectively approve deposit and withdrawal operations, with a 70% consensus threshold required for approval.
This architecture is intended to reduce reliance on centralized intermediaries while giving developers a programmable representation of Bitcoin.
Clarity: Stacks’ Smart Contract Language
Stacks applications are primarily built using Clarity, its smart contract programming language that optimizes for predictability, safety, and security.
Clarity takes a different approach from many popular smart contract languages.
It is an interpreted and decidable language. In practical terms, developers can reason about what a contract will do before executing it, and the code published on-chain is the code that is executed rather than compiled bytecode.
This design emphasizes transparency and predictability, particularly important when smart contracts are responsible for managing financial assets.
Clarity contracts can also read Bitcoin state, enabling developers to create applications that respond directly to activity occurring on Bitcoin.
Combined with sBTC, this gives developers both sides of the equation: the ability to read Bitcoin activity and build programmable applications around Bitcoin capital.
STX Staking
STX is the native token of the Stacks network and plays an important role in its economic and consensus model. One of its most distinctive use cases is staking.
STX staking is not the same as conventional Proof-of-Stake staking.
STX holders participating in staking lock their tokens for defined reward cycles and help support the network's consensus process. Under the Nakamoto architecture, stakers can also participate as signers responsible for validating Stacks blocks.
In return, eligible participants receive BTC rewards generated from the Bitcoin committed by Stacks miners through Proof of Transfer.
This differs from many Proof-of-Stake networks, where validators or delegators generally stake the network's native token and receive rewards denominated primarily in that same token.
With Stacks, the asset being locked is STX, while the underlying PoX reward is BTC.
Another notable difference is that Stacks does not use conventional slashing. STX locked through staking remains in the holder's wallet but becomes temporarily unspendable at the protocol level.
Users can participate through solo staking or delegate their STX through a pool, depending on their holdings and technical requirements.
The Evolution Toward Bitcoin Staking
Stacks is expanding its Proof of Transfer model with Bitcoin Staking, following the approval of SIP-044 and SIP-045. The new mechanism allows BTC holders to earn BTC-denominated yield without moving their Bitcoin off Bitcoin. Holders lock native BTC on Bitcoin Layer 1 alongside STX to form a protocol bond.
Unlike solutions that require bridging or wrapping Bitcoin, Bitcoin Staking is designed to keep BTC on the Bitcoin network and under the holder's own keys. Participants will be able to earn BTC-denominated rewards generated through Proof of Transfer, without protocol-level slashing of their locked BTC.
The Genesis Bond, expected to open in early September 2026, will mark the operational start of Bitcoin Staking, introducing a new way for BTC holders to put their Bitcoin to work for BTC-denominated yield while maintaining self-custody.
Conclusion
Stacks represents a different approach to blockchain scalability and programmability.
Rather than building another standalone smart contract network, it attempts to extend the capabilities of Bitcoin itself through a dedicated execution layer.
The combination of Proof of Transfer, the Nakamoto upgrade, Clarity smart contracts, and sBTC gives Stacks the foundations for a Bitcoin-focused application ecosystem. At the same time, STX staking introduces a unique reward model in which STX holders can participate in network consensus while earning rewards originating in BTC. With Bitcoin Staking soon becoming available, Stacks is taking this model a step further by enabling BTC holders to put native Bitcoin to work while maintaining self-custody, further expanding opportunities to participate in the Stacks economy.
For users, developers, and infrastructure providers, Stacks is therefore worth watching as the Bitcoin Layer 2 ecosystem continues to evolve.
DISCLAIMER: This is not financial advice. Staking and cryptocurrency investment involve a certain degree of risk, and there is always the possibility of loss, including the loss of all staked digital assets. Additionally, delegators are at risk of slashing in case of security or liveness faults on some PoS protocols. We advise you to DYOR before choosing a validator.
