Fillers Overview
Learn how UniswapX fillers and quoters compete to settle swaps across Ethereum, Arbitrum, Base, and Unichain.
Choose Your Integration Path
| Chain | Auction type | Guide |
|---|---|---|
| Ethereum | RFQ + Exclusive Dutch Auction | Filling on Mainnet, Become a Quoter |
| Arbitrum | Dutch Auction (no RFQ) | Filling on Arbitrum |
| Base, Unichain | Priority Gas Auction | Filling on Priority Chains |
UniswapX fillers compete to settle swaps through permissionless auctions. Use this section to choose a chain, ingest orders, and fill safely.
How Filling Works
- Retrieve open orders from the Uniswap API.
- Decode and evaluate each order with your strategy, inventory checks, and risk controls.
- Submit
executetransactions to the target reactor, ensuring required output amounts are met.
Troubleshooting
For common RFQ, webhook, and execution issues, see the Filler FAQ.