Bitcoin Layer 2 implementations are programmable protocols that transform how people use Bitcoin for everyday transactions.
Faster, cheaper, and more scalable payments than the base layer alone.
This article explains the main protocols, their key implementations, and what role each one plays in the evolving Bitcoin L2 ecosystem.
Full List of Bitcoin Layer 2 Implementations
| Protocol | Implementation | Type | Notes | Official website |
|---|---|---|---|---|
| Lightning | LND | Node daemon | One of the four major Lightning implementations. | lightning.engineering |
| Lightning | Core Lightning (CLN) | Node daemon | Formerly c-lightning; modular and plugin-friendly. | blockstream.com/lightning |
| Lightning | Eclair | Node daemon | Scala implementation, commonly used for routing and wallet infrastructure. | acinq.co/eclair |
| Lightning | LDK | Library / SDK | Embeddable Lightning toolkit, not a full node daemon. | blockstream.com/ldk |
| Ark | Bark | Implementation / app stack | Second’s Rust implementation of Ark on Bitcoin mainnet. | second.tech |
| Ark | ark-bitcoin/bark | Codebase / mirror | GitHub mirror of Bark, the Ark implementation. | second.tech |
| Spark | Spark | Protocol implementation / product | Spark Money’s Bitcoin L2 implementation/product. | spark.money |
| Mercury Layer | Mercury Layer | Statechain implementation | Mentioned as a Bitcoin L2 implementation in the landscape. | mercurylayer.com |
| Liquid | Liquid Network | Federated sidechain | The live Liquid network and its ecosystem tooling are the implementation layer. | liquid.net |
| Rootstock | Rootstock (RSK) | Sidechain | Main implementation of the RSK protocol. | rootstock.io |
| RGB | RGB implementations | Client-side validated protocol stack | RGB is usually represented by wallets, libraries, and node tooling rather than one canonical daemon. | rgb.tech |
| Fedimint | Fedimint | Federated ecash implementation | Community and modular deployments exist under the Fedimint stack. | fedimint.org |
| Cashu | Cashu | Federated ecash implementation | Cashu mints and wallet software are the main implementations. | cashu.space |
| Citrea | Citrea | ZK rollup implementation | Citrea’s own stack is the implementation. | citrea.xyz |
| BOB | BOB | Bitcoin rollup / app stack | BOB’s project stack is the implementation. | bbn.com |
| Botanix | Botanix | Bitcoin EVM layer | Botanix’s network/project stack is the implementation. | botanixlabs.com |
| Starknet on Bitcoin | Starknet | Bitcoin-connected L2 stack | Starknet’s Bitcoin-facing stack is the implementation. | starknet.io |
| Bitcoin OS | Bitcoin OS | Verification / rollup stack | Bitcoin OS’s project stack is the implementation. | bitcoinos.org |
| BitVM-style rollups | BitLayer | Rollup project | One of the listed BitVM-style Bitcoin L2 projects. | bitlayer.org |
| BitVM-style rollups | SatoshiVM | Rollup project | One of the listed BitVM-style Bitcoin L2 projects. | satoshivm.io |
| BitVM-style rollups | BSquared Network | Rollup project | One of the listed BitVM-style Bitcoin L2 projects. | bsquared.network |
| BitVM-style rollups | Bison Labs | Rollup project | One of the listed BitVM-style Bitcoin L2 projects. | bisonlabs.io |
| BitVM-style rollups | LumiBit L2 | Rollup project | One of the listed BitVM-style Bitcoin L2 projects. | lumibit.io |
| Lightning-adjacent | OmniBolt | Payment extension | Lightning-adjacent payment project. | omnibolt.network |
| Lightning-adjacent | BiHelix | Payment extension | Lightning/RGB-oriented payment infrastructure. | bihelix.org |
Table of Contents
What Are Bitcoin Layer 2 Implementations?
Bitcoin Layer 2 (L2) refers to protocols built on top of the Bitcoin blockchain that process transactions off-chain or in specialized environments, while still ultimately settling on Bitcoin. Implementations are the concrete software stacks, node daemons, libraries, or networks that bring each protocol to life. 
In the table you created, each protocol (like Lightning or Ark) has one or more implementations (like LND or Bark). Understanding these implementations is crucial for developers, businesses, and power users who want to integrate Bitcoin payments in a scalable way.
Lightning Network: The Backbone of Bitcoin Payments
The Lightning Network is the most mature and widely deployed Bitcoin Layer 2 solution for instant, low-fee BTC payments. It uses payment channels to route transactions off-chain, then periodically settles to the Bitcoin main chain. In practice, Lightning is powered by several independent implementations:
- LND
LND is one of the most popular Lightning node daemons, focused on usability and a rich API. It’s widely adopted by wallets, merchants, and infrastructure providers, and often the first choice for developers who want a straightforward way to run a Lightning node. - Core Lightning (CLN)
Formerly known as c-lightning, Core Lightning is designed for modularity and extensibility. It exposes a powerful plugin system, making it attractive for advanced operators who want fine-grained control over their routing nodes or custom features. - Eclair
Eclair is a Scala-based Lightning implementation. It powers several routing nodes and infrastructure setups and is often used by services that prefer the JVM ecosystem and its tooling. - LDK (Lightning Development Kit)
LDK is not a full node daemon but a library/SDK for building Lightning functionality directly into applications. It’s ideal if you want to embed Lightning into mobile apps, custom services, or novel environments without running a separate node process.
Together, these implementations make Lightning a flexible payment layer: you can run a standalone node, embed Lightning into your app, or operate a high-performance router, all while interoperating through the same protocol.
Ark and Bark: A New Approach to Bitcoin Payments
Ark is an emerging Bitcoin Layer 2 protocol designed around the idea of shared UTXOs and off-chain “virtual” balances, aiming to simplify self-custodial payments and reduce the complexity associated with managing channels.
- Bark
Bark is Second’s Rust-based implementation of the Ark protocol on Bitcoin mainnet. It focuses on delivering fast, low-cost, self-custodial payments for end users and developers. Instead of requiring users to manage channels and liquidity, Bark abstracts much of that complexity while retaining a Bitcoin-native foundation. - ark-bitcoin/bark (codebase)
This is essentially the code and tooling behind Bark, acting as the technical implementation of Ark. For developers, this repository is where the protocol becomes usable code they can integrate or extend.
Ark and Bark represent a different philosophical approach than Lightning: instead of channel-heavy infrastructure, they aim for shared, pre-signed structures that allow many users to benefit from fewer on-chain UTXOs.
Sidechains and Statechains: Liquid, Rootstock, Mercury Layer
Beyond channel-based protocols, Bitcoin L2 also includes sidechains and statechains that create separate environments anchored to Bitcoin.
- Liquid Network
Liquid is a federated sidechain designed for fast settlement, confidential transactions, and asset issuance. As an implementation, the Liquid Network provides its own nodes, wallets, and tooling, but ultimately pegs Bitcoin into the sidechain and back out again. It’s often used by exchanges, trading platforms, and high-volume users who need rapid, predictable settlement. - Rootstock (RSK)
Rootstock is a smart-contract sidechain anchored to Bitcoin, bringing EVM-style programmability into the Bitcoin ecosystem. The RSK implementation allows developers to build DeFi, lending, and other programmable finance applications while still using BTC as the base asset (via a peg). - Mercury Layer
Mercury Layer is a statechain-based implementation, focusing on off-chain transfers of UTXO ownership without moving coins on-chain for each transaction. This is particularly useful for reducing on-chain footprint while still preserving Bitcoin-level security assumptions for owners.
These systems expand Bitcoin’s use cases beyond simple payments, enabling programmable logic, advanced settlement flows, and more complex financial applications.
Ecash Protocols: Fedimint and Cashu
Privacy-preserving, federated ecash protocols are another major pillar of Bitcoin L2 for payments.
- Fedimint
Fedimint is a federated ecash system where communities or organizations run mints that issue ecash tokens backed by Bitcoin. As an implementation, the Fedimint stack includes server software and wallets that allow users to transact rapidly and privately within a federation. - Cashu
Cashu is a lightweight, modular ecash implementation. It focuses on simple, privacy-preserving payments via mints, making it easy to spin up small-scale, community-driven payment systems. The Cashu implementation consists of mints and wallet software that speak the same protocol.
Both Fedimint and Cashu aim to make private, local, and community-centric Bitcoin payments simple and fast, while still letting users anchor back to Bitcoin when needed.
RGB: Client-Side Validated Assets on Bitcoin
RGB is a protocol for client-side validated assets and smart contracts on top of Bitcoin. Instead of pushing all logic and data on-chain, RGB keeps most validation off-chain in clients, dramatically reducing congestion.
- RGB implementations
In practice, RGB is represented by libraries, wallets, and node-like software that manage RGB contracts and assets. There isn’t a single canonical “RGB node” in the same sense as Lightning; instead, multiple implementations cooperate through the shared protocol.
RGB enables complex asset transfers and programmable behavior while using Bitcoin as a settlement anchor. For payments, this can mean stablecoin transfers, tokenized BTC flows, or other asset-based transactions.
Rollups and EVM Layers: Citrea, BOB, Botanix, Starknet, Bitcoin OS
Bitcoin rollups and EVM-compatible layers are designed to bring smart contracts and high-throughput computation into the Bitcoin context.
- Citrea
Citrea’s implementation is a ZK rollup anchored to Bitcoin, offering EVM compatibility with a focus on scalability and security. Developers can deploy smart contracts and apps that ultimately settle to Bitcoin. - BOB
BOB is a rollup/app stack that combines Bitcoin settlement and EVM-like functionality. Its implementation includes the core rollup infrastructure and tools for building applications. - Botanix
Botanix provides an EVM-compatible Bitcoin layer, with its implementation focused on bridging BTC and EVM ecosystems, enabling DeFi and other smart-contract use cases with Bitcoin at the core. - Starknet (on Bitcoin)
Starknet, originally an Ethereum L2, is expanding towards Bitcoin-related settlement. The implementation connects Starknet’s high-throughput, proof-based environment to Bitcoin’s base layer. - Bitcoin OS
Bitcoin OS is a verification and rollup stack built to support trust-minimized settlement and complex applications anchored to Bitcoin. Its implementation includes infrastructure for running and verifying rollups.
These implementations are critical for the “Bitcoin DeFi” narrative: they allow developers to build complex applications while maintaining Bitcoin’s role as the ultimate settlement backend.
BitVM-Style Rollups and Experimental L2s
BitVM-style projects explore using Bitcoin’s script and off-chain proofs to build more advanced L2s without changing Bitcoin’s base layer consensus.
- BitLayer
BitLayer is a rollup project implementing BitVM-style logic to scale Bitcoin and support richer applications. - SatoshiVM, BSquared Network, Bison Labs, LumiBit L2
These implementations follow similar patterns: off-chain computation and proof systems that anchor results to Bitcoin. Each project has its own design choices and roadmap, but they share the goal of scaling Bitcoin without sacrificing decentralization.
These experimental implementations are important for the future of Bitcoin scalability and programmability, even if they are earlier-stage than Lightning or Liquid.
Lightning-Adjacent Implementations: OmniBolt and BiHelix
Finally, there are implementations that extend the Lightning paradigm or weave it together with other protocols:
- OmniBolt
OmniBolt focuses on extending Lightning-like functionality to assets and more complex payment models. It’s Lightning-adjacent, meaning it builds on familiar ideas but goes beyond simple BTC channel payments. - BiHelix
BiHelix integrates RGB and Lightning concepts, aiming to provide infrastructure for Bitcoin-native applications that need both asset functionality and instant payments.
These implementations sit at the intersection of multiple L2 stacks, showing how the ecosystem is starting to converge into combined payment and asset layers.
Why This Table Matters for SEO and Research
From an SEO perspective, this structured overview of Bitcoin Layer 2 protocols and implementations helps answer several high-intent queries:
- “What are the main Bitcoin Layer 2 solutions?”
- “Bitcoin Lightning implementations: LND vs Core Lightning vs Eclair vs LDK”
- “Ark vs Lightning vs Liquid: which Bitcoin L2 should I use?”
- “Bitcoin rollups and EVM layers: Citrea, BOB, Botanix explained”
- “Fedimint vs Cashu vs RGB: Bitcoin ecash and asset protocols”
By listing each implementation in its own row and explaining the role of each protocol, you create a reference article that can rank for many related keywords while providing genuinely useful context for readers.
If you tell me which audience you’re targeting (developers, merchants, or retail users), I can adapt this into a more opinionated guide that recommends which implementations they should start with.
