The 0x API provides methods to source liquidity from 0x Mesh, Kyber, Uniswap, Oasis, and decentralized exchange networks. With the API, developers can route transactions across decentralized exchange networks to find the lowest slippage possible. 0x API automatically creates an order that can be passed directly to smart contracts to be settled on-chain. No API key is required. 0x offers liquidity, fast response times and low revert rates, flexible integration, and open-source terms.