Bitcoin is excellent for transferring and storing value, but its base layer was not designed to run complex DeFi applications in the same way as Ethereum. Rootstock aims to fill that gap by bringing smart contracts and decentralized finance to Bitcoin without changing Bitcoin’s core protocol.
So, what is Rootstock exactly, how is it connected to Bitcoin, and why does it use an asset called rBTC?
Rootstock is an EVM-compatible Bitcoin sidechain that enables smart contracts and decentralized applications to operate within an ecosystem connected to Bitcoin.
A sidechain is an independent blockchain connected to another network — in this case, Bitcoin — allowing assets to be used under different rules and with additional functionality.
Rootstock, originally known as RSK, has been live since 2018. Its goal is to combine two key elements: the ability to build programmable applications with smart contracts and security supported by Bitcoin miners through merged mining.
This makes it possible to use BTC as the foundation for activities that are difficult to implement directly on Bitcoin’s base layer, including decentralized exchanges, lending, liquidity pools, and other DeFi applications.
Rootstock has its own blockchain, blocks, and transactions. Smart contracts are not executed directly on the Bitcoin blockchain.
The connection between the two ecosystems relies mainly on three components: merged mining, rBTC, and PowPeg.
Rootstock uses Proof of Work and allows Bitcoin miners to participate through merged mining.
With merged mining, miners can contribute to the security of both Bitcoin and Rootstock without having to dedicate the same computing power separately to each network.
This is why Rootstock is often described as being “secured by Bitcoin.” However, that statement requires some nuance: Rootstock benefits from Bitcoin’s mining infrastructure, but it remains a separate blockchain with its own protocol and security assumptions.
The result is a smart contract network that can leverage Bitcoin’s mining ecosystem while offering functionality that does not exist directly on Bitcoin’s base layer.
rBTC is the native asset of Rootstock and maintains a 1:1 relationship with BTC.
Within Rootstock, rBTC serves a role similar to ETH on Ethereum. Among other things, it is used to pay transaction fees and cover the gas required to execute smart contracts.
The important distinction is that rBTC is not designed as an independent cryptocurrency with its own separate monetary policy. Instead, it is linked to bitcoin through a mechanism connecting the two networks.
This allows users to bring value from Bitcoin into Rootstock, use it across DeFi applications, and later move back toward BTC.
PowPeg is the native two-way mechanism that connects Bitcoin and Rootstock.
In simplified terms, it allows BTC to be locked on the Bitcoin side while the corresponding amount of rBTC becomes available on Rootstock. The process can also work in the opposite direction when users want to move value back to Bitcoin.
This mechanism is important because it makes bitcoin usable within smart contracts without requiring changes to Bitcoin’s consensus rules.
It also creates a bridge between two different environments: Bitcoin remains focused on its base monetary functionality, while Rootstock provides a programmable environment where BTC-based value can interact with decentralized applications.
One of Rootstock’s most important features is its compatibility with the Ethereum Virtual Machine (EVM), the execution environment widely used for Ethereum smart contracts.
This means developers can work with familiar technologies such as Solidity and common EVM development tools instead of learning a completely different programming environment.
That compatibility can significantly reduce the friction involved in building on Rootstock. Applications and infrastructure originally designed for EVM environments may have a more straightforward path toward supporting Rootstock.
For users, EVM compatibility also means they can interact with Rootstock through wallets that support EVM networks, such as MetaMask, once the network is properly configured.
One of Rootstock’s main use cases is Bitcoin DeFi, also known as BTCFi: using BTC-based value inside programmable financial applications.
For example, Rootstock can support applications for swapping assets through decentralized exchanges, providing liquidity, using supported assets as collateral, accessing lending markets, or participating in other decentralized financial strategies.
The difference compared with simply holding BTC is significant.
On Bitcoin, BTC primarily functions as a monetary asset and store of value. Within Rootstock, its corresponding representation can become part of programmable financial applications.
This gives bitcoin additional utility without requiring Bitcoin itself to support the same smart contract architecture as Ethereum.
A common misconception is that Rootstock operates directly “inside” Bitcoin.
It does not. Rootstock is a separate blockchain connected to Bitcoin.
Although some sources may broadly describe it as a Bitcoin Layer 2 solution, it is more technically precise to describe Rootstock as a Bitcoin sidechain.
Rootstock should also not be confused with the Lightning Network.
Lightning is primarily designed to enable faster and lower-cost bitcoin payments through payment channels. Rootstock, by contrast, is designed as a programmable environment for smart contracts and decentralized applications.
The two technologies therefore address different needs within the broader Bitcoin ecosystem.
Rootstock stands out by combining BTC, EVM compatibility, and smart contracts. For developers, this makes it possible to build applications using tools that are already widely adopted across the Ethereum ecosystem. For users, it opens up new ways to use bitcoin in DeFi applications without changing Bitcoin’s base layer.
When using Rootstock, users move beyond simply holding BTC on the Bitcoin network and can interact with a broader ecosystem of smart contracts, protocols, and decentralized applications. This enables access to features such as swaps, liquidity provision, lending, and other Bitcoin-based financial tools.
As with any DeFi ecosystem, it is important to understand how each protocol works before interacting with it. Factors such as smart contract design, the mechanisms used to move assets between networks, available liquidity, and private key management can all affect the user experience.
Rootstock expands the utility of bitcoin while maintaining a clear separation between the two networks: Bitcoin continues to serve as the monetary layer, while Rootstock adds an EVM-compatible programmable environment for building applications and financial services around BTC.
This approach addresses one of the most important questions in the Bitcoin ecosystem: how can bitcoin become more programmable without turning Bitcoin’s base blockchain into Ethereum? Rootstock’s answer is to keep both functions separate while allowing them to complement each other.
