What a gasless swap is
Every on-chain transaction needs gas, paid in the network's native token: ETH on Ethereum and most layer 2s, BNB on BNB Chain, AVAX on Avalanche, POL on Polygon. If you hold USDC but no ETH, a regular swap is stuck.
A gasless swap removes that requirement. Instead of sending a transaction, you sign a message that says “sell this amount of token X for at least Y of token Z before this time”. ChainBridge hands the signed order to 0x, whose relayer submits the transaction and pays the gas. The relayer's gas cost is taken out of the trade, in the token you sell, and is already counted in the amount you are quoted.
How it works on ChainBridge
Request a quote
With your wallet connected, the router asks 0x Gasless alongside 0x, KyberSwap and ParaSwap. The gasless quote is ranked on net amount like the others; if it wins, it is the route shown.
Sign the approval, if needed
The first time you sell a token, 0x may include a gasless approval for tokens that support signed permits (EIP-2612). Tokens without that feature need an ordinary on-chain approval first, which does cost gas.
Sign the trade
Your wallet shows a typed EIP-712 message with the trade details. Before you sign, ChainBridge checks that the contract named in it is the current 0x settlement contract.
0x executes
ChainBridge submits the signatures to 0x, and the relayer sends the transaction on-chain with its own gas.
Track the result
The order is tracked across the app until it fills or its deadline passes. If it expires, nothing left your wallet.
What you are signing
EIP-712 is a standard for signing structured data. Instead of an unreadable hex string, your wallet shows named fields you can check:
| Field | Meaning |
|---|---|
| Sell token and amount | Exactly what leaves your wallet. |
| Buy token and minimum amount | The least you accept. The order cannot fill below it. |
| Deadline | After this time the signature is worthless. |
| Nonce | A one-time number, so the same signature cannot be used twice. |
| Spender contract | The 0x settlement contract allowed to execute the order. |
The signature only authorizes that exact trade. The relayer cannot change the tokens, raise the amount sold or lower the minimum received.
Where gasless is available
- Networks: Ethereum, Arbitrum, Base, Optimism, Polygon, BNB Chain and Avalanche. Not on Linea.
- Tokens: you sell an ERC-20 token. Selling the native gas token itself (ETH, BNB, AVAX, POL) needs a regular swap.
- Wallets: a regular wallet (EOA) that can sign typed messages. Smart contract wallets such as Safe cannot provide this signature; ChainBridge points them to an on-chain route. See smart contract wallets.
- Trade size: 0x may decline to quote when a trade is too small to cover the relayer's gas, or when it has no route for the pair.
Gasless vs regular swaps
| Gasless | Regular | |
|---|---|---|
| Who sends the transaction | 0x relayer | You |
| Native token needed for gas | No | Yes |
| How gas is paid | Deducted from the trade | From your native token balance |
| What you sign | One or two typed messages | A transaction (plus a Permit2 message on 0x) |
| If it cannot execute | Order expires, nothing is spent | Revert, gas used is still paid |
| Sell the native token (ETH, BNB...) | No | Yes |
| Smart contract wallets | Not supported | Supported on on-chain routes |
| Linea | Not available | Available |
You do not have to pick one by hand. Because the gasless quote already includes its gas cost and the regular quotes are ranked after their gas, the router shows whichever leaves you more. Gasless tends to win when mainnet gas is high or you hold no native token; on layer 2, a regular route often comes out ahead. More on costs in gas fees explained.