Via L2: Sovereign zkEVM Rollup for Bitcoin
Official GitBook docs for Via L2: Sovereign zkEVM validity rollup anchored to Bitcoin; Celestia DA and a verifier network | EVM programmability & high throughput
Via L2 is a modular sovereign validity-proof zk-rollup for Bitcoin anchored by commitments with a zkEVM execution layer using Celestia for data availability, and a distributed verifier network for proof validation, delivering full EVM programmability with high throughput, cost efficiency, Bitcoin-anchored settlement with reorg-bounded finality, and end-user verifiability.
Users can get started with the user guide
Integration, APIs, runtimes, and node operations: Developer Docs
System design: Technical Specifications for Via's architecture
What is Via L2?
Via is a modular sovereign, validity-proof zk-rollup for Bitcoin with a zkEVM execution layer using Celestia DA that scales throughput without introducing new L1 programmability or custodial trust.
It relies on Bitcoin-native primitives: Taproot for key aggregation, inscriptions/OP_RETURN to record state commitments and governance messages, and a MuSig2 threshold bridge for BTC withdrawals.
For each L2 batch, Via posts a single 32-byte state root to Bitcoin along with a pointer to the batch data on the data-availability layer. A zero-knowledge validity proof is produced off-chain that anyone can verify.
The proof is succinct, small, and fast to verify with cost independent of batch size, so Bitcoin’s on-chain role remains minimal to durable commitments and governance while execution happens off-chain at high throughput and low cost.
Data availability is separated from settlement. Full batch data is made available on Celestia (DA), while Bitcoin serves as the commitment and settlement anchor where L2 state roots and governance actions are periodically recorded.
A distributed verifier network independently validates ZK proofs against the data posted to Celestia and only recognizes batches whose commitments and proofs are consistent. Inscriptions function as state commitment posts and governance instructions, not as an L1 consensus mechanism, allowing Via to build on Bitcoin for securing durable commitments and reorg-bounded finality without embedding complex logic on-chain.
Security and trust assumptions are explicit. L2 correctness relies on the soundness of the validity proofs and on data availability from Celestia; clients can verify proofs and sample DA independently. Economic finality of the posted commitments inherits Bitcoin’s reorg resistance once inscriptions confirm.
The BTC bridge is trust-minimized via MuSig2: withdrawals require a threshold of keys that are governed on-chain (via governance inscriptions) and operationally constrained to sign only for finalized, proven exits.
This approach avoids merged mining and is secured by Bitcoin by anchoring zk-verified batch roots and governance messages on L1, minimizing on-chain footprint, and achieving low fees and high throughput through off-chain execution and data, with validity proofs ensuring correctness.
Via's design minimizes Bitcoin's on-chain footprint by committing only batch roots and governance updates, keeping costs low while avoiding miner dependencies, while delivering full EVM programmability and targeting throughput and cost efficiency well beyond Ethereum L1, all while maintaining Bitcoin‑level settlement guarantees and end‑user verifiability.
How Via L2 Works: Batch Lifecycle and Anchoring
For each L2 batch, Via posts a single 32-byte state root to Bitcoin along with a pointer to the batch data on the data-availability layer. A zero-knowledge validity proof is produced off-chain that anyone can verify. The proof is succinct, small, and fast to verify with a cost independent of batch size. So Bitcoin’s on-chain role remains limited to durable commitments and governance while execution happens off-chain at high throughput and low cost.
Celestia provides data availability, while Bitcoin serves as the commitment and settlement anchor, where state roots and governance actions are periodically recorded. A distributed verifier network, along with end users, fetches batch data from Celestia, verifies the ZK proof against the posted state root, and only accepts batches that match the commitments and proofs.
In this setup, inscriptions are authenticated posts for state commitments and governance activities (such as system wallet updates), rather than an L1 validity consensus mechanism. This separation allows Via to anchor to Bitcoin for reorg-bounded finality and censorship resistance, without embedding complex logic on-chain.
Security and trust assumptions are explicit. L2 correctness depends on the soundness of the validity proofs and the availability of batch data on Celestia; clients can verify proofs and independently sample or audit DA. Once inscriptions confirm, the economic finality of posted commitments inherits Bitcoin’s reorg resistance.
BTC custody is secured through a MuSig2 threshold signer set, with keys and policies defined by on-chain inscriptions. This ensures that custody rules are transparent, auditable, and upgradeable without trusting any single party. Operators are cryptographically constrained to sign only for finalized, validity-proven exits, which eliminates arbitrary withdrawals and protects user funds.
Via is a sovereign rollup anchored by commitments. Via L2 is not merged mined (auxpow), or a sidechain like Rootstock, Botanix Spiderchain, or Tether Plasma XPL. Sidechains depend on external guardian or validator sets, often using rotating threshold multisigs, which do not enforce state correctness or withdrawals in their L1 checkpoints.
In contrast to these sidechains, Via's custody and exits are enforced by posted commitments and ZK validity proofs, with a MuSig2 threshold signer set bound by on‑chain policies.
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