Skip to main content

GET /tx-relay/v1/swap/submit

If your user accepts the quote and wants to trade, you do a POST to /tx-relay/v1/swap/submit.

Gasless Approvals​

If a token supports gasless approvals, a meta-transaction may be submitted along with an approval object. You will be able to tell if the sell token is supported by gasless approvals by checking the response of /quote and looking for

const { approval } = response;
approval.isRequired // whether an approval is required for the trade
approval.isGaslessAvailable // whether gasless approval is available for the sell token

To take advantage of gasless approvals, you must also have your user sign the approval.eip712

object returned at the time of the /quote. You can pass the approval.eip712 object to eth_signTypedData_v4 (see MetaMask docs) or function of your choice as the “params” .

Keep in mind that the domain field of this object must follow a strict ordering as specified in EIP-712:

  • name , version, chainId, verifyingContract, salt
    • Contracts may not utilize all of these fields (i.e. one or more may be missing), but if they are present, they must be in this order
  • Any other field must follow in alphabetical order

The approval.eip712 object will present the correct ordering, but make sure that this ordering is preserved when obtaining the signature.

If you choose to compute the approval hash from approval.eip712, it should match approval.hash field.

Meta-transaction Liquidity​

Similar to gasless approval, to submit an meta-transaction trade, you must have your user sign trade.eip712 object returned at the time of the /quote. All the instructions & caveats are the same as previous section.

Example Request​

curl -X POST '<https://api.0x.org/tx-relay/v1/swap/submit>' --header '0x-api-key: <API_KEY>' --header '0x-chain-id: 137' --data '{
 "trade": {
   "type": "metatransaction_v2", // this is trade.type from the /quote endpoint
   "eip712": { /* this is trade.eip712 from the /quote endpoint */ },
   "signature": {
     "v": 27,
     "r": "0xeaac9ddbbf9b251a384eb4a545a2800a6d7aca4ceb5e5a3154ddd0d2923533d2",
     "s": "0x601deadfd33bd8b0ad35468613eabcac0a250a7a32035e261a13e2dcbc462e49",
     "signatureType": 2
    }
  },
 "approval":{
     "type": "permit", // this is approval.type from the /quote endpoint
     "eip712": {/* this is approval.eip712 from the /quote endpoint */},
     "signature": {
       "v": 28,
       "r": "0x55c26901285d5cb4d9d1ebb2828122fd6c334b343901944d34a810b3d2d79773",
       "s": "0x20854d829e3118c3f780228ca83fac6154060328a90d2a21267c9f7d1ae9e53b",
       "signatureType": 2
    }
  }
}'

Example Response​

{
  "type": "metatransaction_v2",
  "tradeHash": "0xde5a11983edd012047dd3107532f007a73ae488bfb354f35b8a40580e2a775a1",
}

More information on signing 0x orders is available here.