Layer 2 & Scaling

Beyond Lightning — BitVM, Rootstock, Stacks, Babylon and other Bitcoin Layer 2s. Their design philosophies and real-world progress.

4 min readLast updated: August 15, 2026

Key points

Beyond Lightning, Bitcoin hosts a range of Layer 2s — Liquid, Rootstock, Stacks, BitVM, and Babylon — each choosing different trade-offs among speed, privacy, and smart-contract capability. L2 development is increasingly viewed as a pillar supporting the Bitcoin economy's sustainability as post-halving miner rewards shrink.

Why Layer 2?

Bitcoin's base layer prioritizes "anyone in the world can run a full node." The block size limit (~4MB) and 10-minute block interval are the consequences of this design philosophy.
This constraint caps theoretical throughput at ~7-14 transactions per second — far below what a global payment infrastructure requires.
Layer 2 (L2) is a protocol built atop Bitcoin's base layer. Many transactions are processed on L2, with only final settlements recorded on the base layer — achieving scalability.
L2s inherit Bitcoin's security (Proof of Work, decentralization) while each makes its own trade-offs (speed / privacy / smart-contract capability).
Unlike Ethereum's L2s (Arbitrum, Optimism, etc.), Bitcoin's L2s use diverse technical approaches — no single standard has emerged.

Lightning Network (the most mature L2)

Launched 2018. The most widely adopted Bitcoin L2, built on Payment Channels, specialized for micro-payments and instant settlement.
As of 2026: ~4,400–5,000 BTC public capacity, ~40,000 public channels. Deployed in El Salvador's Chivo Wallet, Strike (US), Nostr ecosystem (Japan), and more.
March 2026: Tether launched USDT on Lightning Network (via Taproot Assets). Dollar-denominated stablecoin payments on a Bitcoin L2 became reality.
LSPs (Lightning Service Providers) evolved to enable mobile payment UX without users needing to manage channels themselves.
See the dedicated "Lightning Network Primer" topic for deep-dive coverage.

Liquid Network (Federated Sidechain)

A federated sidechain launched in 2018 by Blockstream (a major Bitcoin Core developer company).
Uses L-BTC (Liquid Bitcoin), a 1:1 pegged Bitcoin version. Bi-directional peg with mainnet Bitcoin.
Features: 2-minute fast blocks, Confidential Transactions (privacy), Issued Assets (multiple currencies/tokens).
Governed by a federation of ~15 members (exchanges, institutions) via multisig. Less decentralized than Bitcoin itself, but used for institutional trading and exchange-to-exchange OTC settlement.
Tether issues USDT-Liquid, used for OTC settlement between major exchanges.

Rootstock (RSK) & Stacks

Rootstock (RSK): An EVM-compatible sidechain merge-mined with Bitcoin. Launched 2018. Runs Ethereum-compatible smart contracts on Bitcoin.
Stacks: Uses its own Proof of Transfer (PoX) consensus. Stacks miners send BTC to stackers (STX stakers) in exchange for STX block rewards.
Stacks 3.0 (Nakamoto Release, 2024) enhanced Bitcoin finality integration. Stacks transactions are "anchored" into Bitcoin blocks, inheriting security.
sBTC (2024) is a non-custodial BTC implementation on Stacks, aimed at achieving trustless bridging between both chains.
Though called Bitcoin L2s, these have their own consensus and tokens — "affiliated chain" is a more accurate characterization.

BitVM (Proposed 2023)

October 2023: Robin Linus published a groundbreaking idea enabling arbitrary computation verification on Bitcoin.
Rather than adding new Bitcoin Script operations, it uses "fraud proofs" for optimistic execution. On-chain verification runs only when results are disputed.
Mechanistically similar to Ethereum's Optimistic Rollups — theoretically enabling Turing-complete computation as a Bitcoin L2.
Post-2023: BitVM1, BitVM2, and improvements followed. Multiple projects (Bitlayer, Citrea, BOB) are building BTC L2s based on BitVM.
Practical deployment has challenges (potentially requiring many on-chain transactions in worst cases), but opened a new frontier in Bitcoin L2 design.

Babylon (BTC Staking)

Founded 2022, mainnet launched 2024. A mechanism enabling BTC holders to participate in validating other PoS chains by time-locking Bitcoin L1 keys.
BTC remains on mainchain — enabling "self-custody staking." Unlike traditional staking, keys are never held by a third party.
If the Babylon PoS chain (BBN) or integrated chains detect misbehavior, a specially structured time-lock on the BTC key enables slashing.
BTC staking spread rapidly 2024-2026. "Restaking" projects (Lorenzo, Pendle, etc.) built on Babylon have emerged.
Provides a new yield source for BTC holders, while sparking debate about "Bitcoin purity."

Ark, Fedimint & the New Generation

Ark: A protocol targeting instant payments via a different mechanism than Lightning. Instead of long-term channels, uses a joint-holdings shared-UTXO model.
Fedimint: A federated Bitcoin custody system based on Chaumian ecash. High privacy, functioning as a community/family-scale Bitcoin bank.
Cashu: A similar ecash protocol — more lightweight and developer-friendly than Fedimint.
These next-generation protocols address Lightning's complexity around liquidity and channel management.
Experimental as of 2026, but gaining adoption particularly in privacy-focused communities.

Layer 2 Comparison

Lightning: fast ✓, private ✓, smart contracts ✗. Use case: micro-payments.
Liquid: fast ○, private ○ (confidential txs), smart contracts △. Use case: institutional trading.
Rootstock: fast ○, private ✗, smart contracts ✓ (EVM-compatible). Use case: DeFi.
Stacks: fast ○, private ✗, smart contracts ✓ (Clarity language). Use case: NFTs and apps.
BitVM: fast △ (in development), private ✗, smart contracts ✓ (arbitrary computation). Future-oriented.
Babylon: BTC staking specialization. Less "L2" and more "BTC asset utilization protocol."

Outlook

To compensate for post-halving miner-reward reductions, layers dependent on on-chain fees face long-term challenges. L2 development is a pillar supporting the entire Bitcoin economy.
Ironically, Ordinals/Runes have energized the Bitcoin fee market, supporting miner revenue.
If cross-L2 atomic swaps become practical, Lightning ↔ Liquid ↔ Stacks interoperability improves.
Practical BitVM-family L2s could enable Ethereum-compatible DeFi on Bitcoin.
Critics argue L2 proliferation sacrifices Bitcoin's "simplicity." The L2 that dominates will be determined by competition over the coming years.