At a glance
Across Protocol ↗ and Synapse Protocol ↗ both route value across chains, but their engines differ. Across uses an intent-based model where relayers compete to fill user orders, optimizing for speed and capital efficiency. Synapse is a liquidity router that also provides a generalized message-passing layer. With $200M in TVL versus Synapse's $50M, Across has deeper liquidity, while Synapse covers over 19 chains compared to Across’s 10. Choose Across for fast L2-to-L2 transfers, Synapse for broader chain reach and interchain messaging.
Key differences
TVL and liquidity depth: Across holds $0.2B TVL, four times Synapse’s $0.05B. This deeper liquidity pool reduces slippage on larger transfers and supports faster relay execution.
Chain coverage: Across spans 10 chains—including Ethereum, Arbitrum, Optimism, Base, Polygon, zkSync, Linea, Blast, Mode, and Scroll. Synapse covers the same core networks (Ethereum, Arbitrum, Optimism, Polygon, BNB, Avalanche, Base, Linea, Blast) plus “+10 more,” giving it an edge if you need obscure EVM chains or non-EVM environments.
Mechanism: Across uses optimistic verification via UMA and a relayer network to settle transfers in seconds. Synapse employs liquidity pools and AMMs, with its Interchain Network offering arbitrary message passing. Across’s intent model is generally faster for simple asset transfers; Synapse’s messaging layer enables dApps to build cross-chain logic.
Ecosystem integration: Across powers the bridge flows inside Uniswap and Coinbase Wallet, signaling deep product-market fit. Synapse’s messaging is used by a handful of DeFi apps, but none at that scale.
Age and audits: Synapse launched in 2021, a year earlier. Across (2022) has three audits (OpenZeppelin, Mixbytes, Code4rena), while Synapse has two (Quantstamp, Certik).
Security and track record
Both protocols have clean incident records. Across has been audited by OpenZeppelin, Mixbytes, and Code4rena, providing broad coverage of its smart contracts and off-chain relayer logic. Synapse is backed by Quantstamp and Certik audits. Across’s slightly larger audit set and its use of UMA’s optimistic oracle—itself well-audited—add a layer of economic security that Synapse’s vanilla pool model lacks. Over three years of operation, neither has suffered an exploit, suggesting comparable battle-testedness. If you weigh audit surface area, Across holds a slim edge.
Fees and costs
Specific fee structures are not disclosed in our data for either protocol. Across’s relayer competition model typically yields low-cost, fast fills, while Synapse’s AMM-based swaps incur pool fees that vary by chain and asset. The exact cost at any moment depends on gas prices, relayer inventory, and pool composition. For current fee estimates, refer to the official docs or fee calculators on each protocol’s website.
Which should you choose
Pick Across Protocol if you:
- Transfer assets between EVM L2s like Arbitrum, Optimism, or Base and want sub-minute settlement.
- Value deep liquidity that minimizes slippage on large swaps.
- Prefer a bridge integrated into Uniswap and Coinbase Wallet for a seamless experience.
Pick Synapse Protocol if you:
- Need to bridge to a chain not supported by Across (e.g., Avalanche, BNB, or the “+10 more” cohorts).
- Build or interact with dApps that leverage Synapse’s arbitrary message-passing for cross-chain logic.
- Have historically used Synapse and value its DAO and familiar UX.
Verdict
Across Protocol wins for most retail cross-chain use cases. Its intent-based design delivers speed, its $200M TVL provides depth, and its role as the engine behind Uniswap and Coinbase Wallet bridges demonstrates reliability. Synapse remains relevant for edge-chain access and interchain messaging needs, but for the typical bridge user in 2026, Across is the stronger choice.