Simulate Transactions#
Simulate a blockchain transaction before executing it to see the expected outcomes and potential risks.
Transaction simulate API is available to our enterprise customers only. If you are interested, please contact us [email protected].
Request URL#
GET https://web3.okx.com/api/v5/dex/pre-transaction/simulate
Request Parameters#
| Parameter | Type | Required | Description |
|---|---|---|---|
| fromAddress | String | Yes | Source address. |
| toAddress | String | Yes | Destination address. |
| chainIndex | String | Yes | Unique identifier for the chain. e.g., 1: EthereumSee Supported Chains for more. It supports EVM、SOL、SUI, more chains will be supported soon. |
| txAmount | String | No | Transaction amount. Default value: 0. 1. For Native token transactions ( where the fromToken is native token. e.g., Ethereum), the txAmount can be set to the native token quantity, or retrieved from /swap api(e.g., txAmount = swapResponse.tx.value). 2.For non-native token transactions, set txAmount to 0. The valle must use base unit of the native token, e.g., wei for ETH |
| extJson | Object | Yes | Extended information object containing the following fields: |
| > inputData | String | Yes | Call data for the transaction. |
| priorityFee | String | No | Priority fee. Only applicable to Solana. |
| gasPrice | String | No | Gas price for the transaction. |
Response Parameters#
| Parameter | Type | Description |
|---|---|---|
| intention | String | Transaction purpose. Valid values: "Swap", "Token Approval" |
| assetChange | Array | Details of asset changes resulting from the transaction |
| > assetType | String | Asset type. Valid values: "NATIVE", "ERC20", "SPLTOKEN"，"SUITOKEN" |
| > name | String | Asset name (e.g., "Ethereum") |
| > symbol | String | Asset symbol (e.g., "ETH") |
| > decimals | Number | Asset decimal precision |
| > address | String | Asset contract address |
| > imageUrl | String | URL to the asset's image |
| > rawValue | String | Asset amount. Positive values indicate receiving assets, negative values indicate sending assets. |
| gasUsed | String | Gas consumed by the transaction |
| failReason | String | Human-friendly explanation if the transaction would fail |
| risks | Array | Potential risks identified in the transaction |
| > address | String | Address associated with the risk |
| > addressType | String | Type of address. Valid values: "contract", "eoa" |
Request Example#
shell
curl --location --request POST 'https://web3.okx.com/api/v5/dex/pre-transaction/simulate' \
--header 'OK-ACCESS-KEY: your-access-key' \
--header 'OK-ACCESS-SIGN: your-access-sign' \
--header 'OK-ACCESS-PASSPHRASE: your-passphrase' \
--header 'OK-ACCESS-TIMESTAMP: 2025-05-19T10:00:00.000Z' \
--header 'Content-Type: application/json' \
--data-raw '{
"fromAddress": "0x742d35Cc6634C0532925a3b844Bc454e4438f44e",
"toAddress": "0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D",
"chainIndex": "1",
"txAmount": "0",
"extJson": {
"inputData": "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"
},
"gasPrice": "12000000000"
}'
Response Example#
200
{
"code": "0",
"data": [
{
"intention": "SWAP",
"assetChange": [
{
"assetType": "NATIVE",
"name": "Ether",
"symbol": "ETH",
"decimals": 18,
"address": "",
"imageUrl": "",
"rawValue": "-1000000000000000"
},
{
"assetType": "ERC20",
"name": "USD Coin",
"symbol": "USDC",
"decimals": 6,
"address": "0xa0b86991c6218b36c1d19d4a2e9eb0ce3606eb48",
"imageUrl": "",
"rawValue": "1000000000000000"
}
],
"gasUsed": "180000",
"failReason": "",
"risks": []
}
],
"msg": "success"
}