UniswapX outsources routing complexity to an open network of third-party fillers.
Fillers then compete to fill swaps using on-chain liquidity (like Uniswap v2 or v3) or their own private inventory.
Anyone can become a third party filler for UniswapX swaps. See here for more information on becoming a filler: https://docs.uniswap.org/contracts/uniswapx/overview
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