## Gasless Swaps

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.

## 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.

### No — BYO wallet

### Yes — embedded or custodial

## Which gasless flow should I use?

Does your app control the user's wallet?

### **Permit-based Gasless**  
_Limitation: not all ERC-20s support permit_  
Are you already using ERC-4337?

### **ERC-4337 Gasless**  
### **7702 BatchExecutor**  
Same-chain gasless swaps are only supported if you sponsor the fees. Same-chain swaps route directly through DEXes, due to this the solver never has an opportunity to deduct the gas fees before the user gets the destination token.

## 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 Permit2 message, and Relay’s solver handles everything else — no approval transaction, no gas.

USDC is fully gasless. Other ERC20 tokens require a one-time approval transaction.

### 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

### 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. For subsidizing fees you’ll need to make sure you have [fee sponsorship](https://docs.relay.link/features/fee-sponsorship) set up. See the full working example: [byo-eoa-permit](https://github.com/relayprotocol/relay-gasless-examples/tree/main/byo-eoa-permit)

## 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](https://docs.relay.link/references/api/execute) endpoint instead of directly to the EntryPoint. Relay’s relayer submits the transaction and covers the gas.

### `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.

### 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

### 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. For subsidizing fees you’ll need to make sure you have [fee sponsorship](https://docs.relay.link/features/fee-sponsorship) set up. See the full working example: [4337-gasless](https://github.com/relayprotocol/relay-gasless-examples/tree/main/4337-gasless)

## 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](https://github.com/Uniswap/calibur) or similar), enabling atomic approve + deposit in a single call.

### `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](https://github.com/Uniswap/calibur). Different BatchExecutor contracts may have different gas overheads — adjust this value based on the implementation you use.

### 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](https://docs.relay.link/references/api/execute) targeting the user’s EOA

### 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. For subsidizing fees you’ll need to make sure you have [fee sponsorship](https://docs.relay.link/features/fee-sponsorship) set up. See the full working example: [7702-batch-executor](https://github.com/relayprotocol/relay-gasless-examples/tree/main/7702-batch-executor)