All transactions on the blockchain require a network cost to be processed, but with UniswapX swaps, the filler pays the network costs on swappers’ behalf.
Since swappers don’t have to pay network costs, they don’t need to own/hold networks’ native token (ETH, MATIC, etc.) to swap and they don’t have to pay anything for a failed swaps.
Fillers price the network cost into the swap price, but can lower transaction costs by batching multiple orders or filling orders from their own private holdings.
Swappers still need to pay the network costs under specific circumstances:
- Initial on-chain token approval of Permit2 incurs a network cost
- Native network tokens (ETH, MATIC, etc.) must be wrapped before they can be swapped on UniswapX which incurs a network cost
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