1inch app is where Fusion enables resolver-filled gasless token swaps

Fusion against UniswapX, CoW Swap, and Classic execution

Execution choice decides who submits the onchain transaction, and Fusion most closely resembles UniswapX while differing sharply from 1inch Classic and CoW Swap.

All four routes separate quoting from settlement, but the settlement actor changes the trade-off. 1inch Fusion and UniswapX collect an offchain authorization and let professional fillers carry execution. CoW Swap groups signed orders into batch auctions where solvers seek a clearing outcome. UniswapX relies on an open filler network, while 1inch Fusion limits filling to registered resolvers under its resolver rules. 1inch Classic sends the user’s transaction through the 1inch Aggregation Protocol, which can split liquidity across venues such as Uniswap v3, Curve, and Balancer. Fusion’s distinguishing combination is a resolver auction, a signed minimum return, partial fills, and resolver-funded EVM gas outside Fast mode.

Starting an EVM Fusion order in the 1inch app

A same-chain Fusion swap starts correctly only when the wallet, source token, destination token, and 1inch app all point to the same EVM network.

Connect MetaMask, the 1inch Wallet, Ledger, or another WalletConnect-compatible signer, then select the sell and receive assets on one network. Ethereum uses chain ID 1, while Arbitrum One uses 42161, Base uses 8453, and BNB Chain uses 56. The wallet’s chain must match the quote’s chain before signing. EIP-712 places the chain ID and verifying contract in the signing domain, so a network switch calls for a fresh order. Paste a contract address only when the intended token isn’t in the picker. An EVM address contains 20 bytes and normally appears as 40 hexadecimal characters after the 0x prefix.

After the network and tokens align, enter the sell amount and review the minimum receive, expiry, and execution mode before authorizing. The source balance must cover the complete order, and the selected token allowance must cover the amount a resolver may transfer. A quote remains tied to the selected chain and token contracts.

How does the Dutch auction set the fill rate?

The signed minimum return decides the boundary, and 1inch Fusion lowers the resolver’s offered output along a time-based Dutch-auction curve until settlement.

The quote defines an auction-start amount and an auction-end amount. Early in the window, a resolver receives a narrower economic margin and the user gets a stronger output rate; the curve then moves toward the encoded minimum.

One basis point equals 0.01%, and 100 basis points equal 1%, which helps when comparing small rate differences without confusing them with token decimals. Partial filling lets more than one resolver settle portions of the same order. Each resolver selects a portion it can execute within the curve, so settlement can progress across several blocks and liquidity paths. The interface totals those received portions against the original signed amount. The floor still applies to every permitted fill, and the remainder stays available until another fill or expiry.

Gasless settlement moves the network fee into the quote

Outside Fast mode on EVM networks, Fusion is gasless to the user because a resolver submits settlement and pays the native network fee.

That Fusion order asks the wallet for an EIP-712 signature, so authorizing it consumes 0 units of EVM gas. The resolver later broadcasts one or more settlement transactions and pays ETH, BNB, or another network-native asset. That payment isn’t economically invisible: resolvers include execution cost in the rate they’re willing to accept along the auction curve. Classic mode instead has the wallet submit the router transaction, making the live base fee, priority fee, and route complexity direct user costs.

If an EVM Fusion order expires unfilled, the wallet pays 0 settlement gas and retains control of the offered tokens.

Approvals and signatures are separate permissions

Token allowance decides whether a resolver can transfer the sold ERC-20, while EIP-712 separately proves the wallet accepted this particular order (compare 1inch withdrawals ).

An approval changes a token contract’s allowance and normally costs one onchain transaction when no suitable permit exists. EIP-2612 moves compatible approvals into a signed permit containing a value, nonce, and deadline; the 1inch Limit Order Protocol also supports approval, permit, and Permit2 schemes. The ERC-20 allowance field is a 256-bit unsigned integer, whose maximum value is 2 ²⁵⁶ − 1. A maximum allowance isn’t required for Fusion. A finite amount narrows the permission, while allowance left after transfers remains until the owner changes it or another authorized transfer consumes it. The EIP-712 order signature then binds the maker, assets, amounts, chain ID, verifying contract, and order conditions.

Token decimals shape every amount shown

Token decimals decide how the quoted human amount becomes the integer stored in a Fusion order, so the contract address and precision must agree.

USDC on Ethereum uses 6 decimals, so one smallest unit equals 10 ⁻⁶ USDC. WETH uses 18 decimals, and one wei-denominated unit equals 10 ⁻¹⁸ WETH; likewise, 1 ETH contains 10 ¹⁸ wei. The WETH contract wraps and unwraps ETH at a 1:1 amount before network costs. Fusion carries integer amounts, while the interface applies each token contract’s decimal setting for display.

The token picker pairs each symbol with its network and contract because two assets can reuse a ticker without sharing a decimal definition. For USDC, USDT, WETH, and 1INCH, the chain selection fixes which contract and decimals enter the order. A resolver transfers the contract recorded in the signature.

Network boundaries and the Solana exception

Network selection determines whether gasless EVM Fusion applies, because Solana Fusion publishes the intent onchain and requires a small SOL balance for that transaction.

The broader 1inch interface lists Ethereum, BNB Chain, Polygon, Arbitrum One, Avalanche C-Chain, Base, Gnosis, Linea, Optimism, zkSync Era, Sonic, Robinhood Chain, Unichain, and Solana. Individual features and pairs differ across these networks. Polygon uses chain ID 137, Optimism uses 10, Avalanche C-Chain uses 43114, Gnosis uses 100, Linea uses 59144, and zkSync Era uses 324. On EVM networks, wallet and quote chain IDs must match. On Solana, publishing a Fusion intent starts onchain and consumes SOL; budget that native transaction fee before opening its auction.

Who benefits most from resolver-filled execution?

Fusion fits best when the user values bounded output and resolver-paid EVM settlement more than immediate inclusion in the next available block.

A wallet holding an ERC-20 but no ETH on Ethereum illustrates the cleanest use. An existing allowance or permit lets the holder sign an order without funding the settlement transaction. Larger orders also benefit from partial filling and liquidity sourced by resolvers across the 1inch Aggregation Protocol, private inventory, and market venues. Choose 1inch Classic when direct router execution and user-selected gas timing control the decision.