Across Protocol is an emerging cross-chain bridge built on UMA's Optimistic Oracle. It combines the Optimistic Oracle, relayers, and a single-sided liquidity pool to facilitate decentralized, instant transactions between chains. Currently, it supports networks such as Ethereum, Arbitrum, Optimism, and Polygon.

The protocol allows users to transfer tokens instantly and cost-effectively across different chains by borrowing liquidity from decentralized relayers. Relayers pre-fund users to enable immediate cross-chain transfers, and in return, they are compensated from a single liquidity pool on the Ethereum network.

ACX is the decentralized governance token of Across Protocol, granting holders control over the cross-chain protocol and decision-making authority over the DAO's funds. The total supply of ACX tokens is 1 billion, distributed across four main categories.