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Gas fees add layers of complexity to swapping. Holding the native token, on the right network, at the right time to pay for gas adds friction for users. A gasless swap means that the user only pays with the input token, and this covers all fees. This means someone else is executing the transaction and paying the gas.

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What solution is right for me?

There are many different solutions when it comes to implementing a gasless swap experience. We’ve put together a decision tree below to help you arrive at the solution that best fits your application.

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Permit-based Gasless

Use this approach when your app does not control the user’s wallet (e.g. MetaMask, Rainbow, or any external EOA). The user signs an off-chain EIP-3009 or EIP-2612 permit message, and Relay’s solver handles everything else — no approval transaction, no gas.
Support is limited to USDC, erc20 tokens require a one time approval transaction.

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How it works

1

Get a quote

Call /quote/v2 with usePermit: true
2

Sign the permit

Prompt the user to sign an EIP-712 typed-data permit message (off-chain, no gas)
3

Submit to Relay

Submit the signed permit to Relay
4

Fulfillment

Relay’s solver withdraws tokens from the user’s EOA and fulfills the destination transaction

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Fees

You can choose to subsidize all destination fees by passing subsidizeFees: true to the quote api (this effectively subsidizes the first time approval). The user still needs to pay for the origin gas fee. See the full working example: byo-eoa-permit

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ERC-4337 Gasless

Use this approach if your app already uses ERC-4337 smart accounts. ERC-4337 UserOperations normally require gas fees, either paid by the sender or a paymaster. With Relay, you set all gas fee fields to 0 and submit the handleOps call via Relay’s /execute endpoint instead of directly to the EntryPoint. Relay’s relayer submits the transaction and covers the gas.

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originGasOverhead

Pass originGasOverhead: 300000 in the /quote/v2 request. This tells Relay how much additional gas the UserOperation adds over a normal EOA transaction, used during simulation to accurately price the fee.

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How it works

1

Get a quote

Call /quote/v2 with originGasOverhead: 300000 to get deposit transaction details
2

Build the UserOperation

Build a UserOperation that batches approve + deposit calls via executeBatch
3

Zero out gas fields

Set maxFeePerGas and maxPriorityFeePerGas to 0
4

Sign the UserOperation

Sign the UserOperation with the account owner key
5

Submit via Relay

Encode an EntryPoint.handleOps() call and submit it via POST /execute with subsidizeFees: true
6

Monitor

Poll /intents/status/v3 until the bridge completes

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Fees

You can choose to subsidize origin fees: pass subsidizeFees: true to the execute api executionOptions. You can choose to subsidize destination fees: pass subsidizeFees: true to the quote api. You can choose to subsidize both or none of these. If not subsidized the user pays from the output token. See the full working example: 4337-gasless

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7702 BatchExecutor

Use this approach when your app controls an embedded or custodial wallet and you want gasless execution with any ERC-20 token — not just permit-compatible ones. This leverages EIP-7702 to delegate the user’s EOA to a BatchExecutor contract (Calibur or similar), enabling atomic approve + deposit in a single call.

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originGasOverhead

Pass originGasOverhead: 80000 in the /quote/v2 request. This tells Relay how much additional gas the Calibur execute() wrapper adds over the raw inner calls (EIP-712 signature verification, batch dispatch, nonce check). This is lower than ERC-4337’s 300000 because there’s no EntryPoint or UserOp validation overhead.
The 80000 value is specific to Calibur. Different BatchExecutor contracts may have different gas overheads — adjust this value based on the implementation you use.

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How it works

1

Check delegation

Check if the user’s EOA is already delegated to the BatchExecutor via EIP-7702
2

Get a quote

Call /quote/v2 with originGasOverhead: 80000 to get deposit transaction details
3

Build the batch

Build a BatchedCall that atomically combines approve() and deposit()
4

Sign the authorization

Sign an EIP-7702 authorization (off-chain, no gas) delegating the EOA to the BatchExecutor
5

Submit via Relay

Submit via POST /execute targeting the user’s EOA

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Fees

You can choose to subsidize origin fees: pass subsidizeFees: true to the execute api executionOptions. You can choose to subsidize destination fees: pass subsidizeFees: true to the quote api. You can choose to subsidize both or none of these. If not subsidized the user pays from the output token. See the full working example: 7702-batch-executor