The decentralized exchange launched on Ethereum in 2018 that uses an automated market maker model is Uniswap.
Uniswap is a decentralized exchange protocol that lets users swap tokens through Ethereum smart contracts rather than a centralized company or traditional order book. Its automated market maker system uses liquidity pools: users deposit token pairs, and traders exchange against those pooled assets according to a pricing formula.
Former Siemens mechanical engineer Hayden Adams created Uniswap, launching the first version on November 2, 2018. Adams was inspired in part by a blog post from Ethereum co-founder Vitalik Buterin about decentralized exchanges and on-chain market making.
Liquidity providers receive a share of trading fees in return for supplying assets. Uniswap’s governance token, UNI, was introduced in 2020 and is used for protocol governance, but users do not need UNI simply to trade. Curve, PancakeSwap, and SushiSwap are also decentralized exchanges, but they were not the answer to this specific 2018 Ethereum launch clue.