Crypto Gloss

Across Protocol

Across Protocol is the leading intent-based cross-chain bridge — an architecture that delivers dramatically better user experience than traditional liquidity-pool bridges by separating the user-facing transaction from the underlying settlement mechanism. When you bridge via Across, you don’t wait for a block on the source chain, a block on the destination, and an oracle update — you receive funds on the destination chain within seconds because a professional “relayer” fronts the funds from their own capital. The relayer then gets repaid from the origin chain pool after a canonical proof settles. This design (the “Optimistic Bridging” model) makes Across simultaneously the fastest, cheapest, and most capital-efficient major bridge in DeFi. As of 2025, Across is the protocol of choice for ERC-7683 (cross-chain intents standard) and has become the infrastructure layer for many DeFi aggregators routing cross-chain swaps.

Background: Why Traditional Bridges Are Slow

Traditional bridges (early Stargate, Hop, Connext) work approximately like:

  1. User locks assets in smart contract on source chain
  2. Oracle/relayer observes the lock event
  3. (Wait for finality on source chain)
  4. Oracle/relayer unlocks assets on destination chain
  5. (Wait for oracle confirmation on destination)

Problems:

  • Steps 3–5 require multiple finality windows: 15 minutes to hours for L1 bridges; 1–7 minutes for L2 bridges
  • Each liquidity pool maintains separate reserves on each chain → capital fragmentation
  • Complex multi-chain liquidity management creates MEV and imbalance risks

Across’s Architecture: Intent-Based Bridging

The protocol is built around the following components.

Relayer Model

Across uses a “relayer marketplace” — professional market makers who front funds immediately:

User flow:

  1. User requests bridge: “Send 1 ETH from Arbitrum → Base”
  2. Relayer sees the intent on Arbitrum (order includes: fee offer + expiry)
  3. Relayer sends 0.999 ETH (fee deducted) to user on Base within ~5 seconds
  4. User’s 1 ETH on Arbitrum is deposited to the Across Hub Pool
  5. Periodically (every 15–30 minutes), a “canonical bundler” verifies relayer claims and reimburses relayers from the Hub Pool with profit

From user’s perspective: Near-instant bridge with low fees

From relayer’s perspective: Risk-free arbitrage — they’re overcollateralized by the user’s deposit; the optimistic oracle just needs to confirm the deposit exists before reimbursement

Hub-and-Spoke Model

Unlike bridges with liquidity pools on every chain, Across uses a single Hub Pool (on Ethereum mainnet):

  • Hub Pool: Single canonical pool of USDC, ETH, WBTC on Ethereum
  • Spoke Pools: Lightweight deposit pools on each supported L2 (Arbitrum, Optimism, Base, etc.)
  • Capital flow: User deposits to Spoke Pool → Relayer fronts funds → Bundler settles claims → Hub reimburses relayer

Why this is capital-efficient: One pool serves all chains; no need to maintain $100M on each chain — the relayer float covers instant settlement.

Optimistic Oracle Security (UMA)

Across is secured by UMA Protocol’s Optimistic Oracle:

  • Bundler submits a “root bundle” claiming: “These relayers serviced these requests; pay them back”
  • A 30-minute challenge window allows anyone to dispute incorrect claims
  • If undisputed, root bundle is finalized and relayers reimbursed
  • If disputed → UMA’s decentralized voting system resolves the dispute

Security model: Anyone providing false claim risks having their stake slashed; only economically rational actors participate (relayers who actually fulfilled requests)

ACX Token

Symbol: ACX

Function: Governance token for Across DAO

Distribution strategy: Community-focused; LP incentives for Hub Pool liquidity providers; retroactive airdrop to early users

Protocol revenue flow:

  • Bridge fees (paid by users): ~0.05–0.1% of bridged amount
  • Revenue goes to Hub Pool LPs (liquidity providers) as yield
  • ACX stakers/governance influences fee parameters and protocol upgrades

ERC-7683: Cross-Chain Intents Standard

Across co-authored ERC-7683 (the Cross-Chain Intents Standard) with Uniswap Labs — a pivotal contribution to DeFi infrastructure:

What ERC-7683 does:

  • Standardizes how “intents” (user requests to perform cross-chain actions) are specified
  • Any intent protocol (Across, UniswapX, 1inch Fusion) can use the same format
  • Fillers (solvers/relayers) monitor for intents in standard format across all protocols
  • Creates a competitive marketplace of liquidity providers for cross-chain execution

Why this matters: Without a standard, each bridge implements its own intent format → relayers must integrate each separately. With ERC-7683, a relayer built for Uniswap’s intents automatically works for Across’s intents and vice versa → better competition → lower fees for users.

Adoption: Uniswap X, Hop, deBridge, and others implementing ERC-7683 support

Comparison: Across vs. Other Bridges

Feature Across Stargate V2 LayerZero Wormhole
Architecture Intent/relayer Liquidity pools Message passing Message passing
Speed 2–30 sec 10–60 sec 1–10 min (destination confirmation) 5–30 min
Capital efficiency High (hub-spoke) Low (per-chain pools) N/A (messaging only) N/A (messaging only)
Security model UMA optimistic oracle LayerZero DVN DVN network Guardian network
Token ACX STG ZRO W
Best use case Token bridging Stablecoin liquidity General messaging Wide chain coverage

Social Media Sentiment

Across is a favorite among DeFi power users who’ve run the benchmarks — objectively, on speed vs. fee metrics, Across frequently wins. The ACX airdrop in late 2022 was received positively for its retroactive community distribution. ERC-7683 co-authorship with Uniswap is a significant vote of confidence — Uniswap Lab’s cross-chain design uses compatible intent formats, implicitly endorsing Across’s model. The UMA protocol security is less visible/intuitive than a ZK-proof system, which creates occasional FUD about security, but the optimistic oracle has operated without incident. The main criticism: Across’s community size and marketing presence is significantly smaller than LayerZero or Wormhole despite arguably better technical performance. The team (Hart Lambur, Kevin Chan) is respected for building the right product that lets quality speak for itself — though this “under the radar” positioning risks being overtaken by better-marketed competitors with similar technical specs.

How to Use Across

Bridge cross-chain at across.to — no native token purchase required

To provide liquidity: Deposit ETH/USDC/WBTC to Hub Pool on Ethereum → earn bridge fee yield

ACX available for governance:

Store ACX securely:

Last updated: 2026-04

Sources