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Simulation RPC

Get started with Simulation RPC to simulate transactions with the Tenderly Web3 Gateway node.
Simulation RPC allows you to use your Tenderly Web3 Gateway node not only to read data and send transactions to the blockchain, but also to simulate transactions in one place. It's possible to use Simulation RPC for the networks supported in Web3 Gateway. For other cases, use Simulation API.
Simulation RPC allows you to:
  • Simulate an arbitrary transaction.
  • Select any historical (or latest) block you wish to simulate on and go back in time.
  • Pass a pre-simulation state override map so you can bring contracts participating in the simulation in a specific state, even if you wouldn't be able to on an actual network (e.g. Mainnet).
To get started, take a look at the following three examples:

Performing a single simulation

In this example, we'll do a quick simulation of 0xe2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2 approving 299 to 0xf1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1. Check the Response for the Approve event.
Simulation RPC
Simulation RPC Response
curl https://mainnet.gateway.tenderly.co/$TENDERLY_WEB3_GATEWAY_KEY \
-X POST \
-H "Content-Type: application/json" \
-d \
'{
"id": 0,
"jsonrpc": "2.0",
"method": "tenderly_simulateTransaction",
"params": [
{
"from": "0xe2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2",
"to": "0x6b175474e89094c44da98b954eedeac495271d0f",
"gas": "0x7a1200",
"gasPrice": "0x0",
"value": "0x0",
"data": "0x095ea7b3000000000000000000000000f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1000000000000000000000000000000000000000000000000000000000000012b"
},
"0xfc497b"
]
}'
{
"id": 0,
"jsonrpc": "2.0",
"result": {
"blockNumber": "0xfc497b",
"cumulativeGasUsed": "0x0",
"gasUsed": "0xb412",
"logs": [
{
"anonymous": false,
"inputs": [
{
"name": "src",
"type": "address",
"value": "0xe2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2"
},
{
"name": "guy",
"type": "address",
"value": "0xf1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1"
},
{
"name": "wad",
"type": "uint256",
"value": "299"
}
],
"name": "Approval",
"raw": {
"address": "0x6b175474e89094c44da98b954eedeac495271d0f",
"data": "0x000000000000000000000000000000000000000000000000000000000000012b",
"topics": [
"0x8c5be1e5ebec7d5bd14f71427d1e84f3dd0314c0f7b2291e5b200ac8c7c3b925",
"0x000000000000000000000000e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2",
"0x000000000000000000000000f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1"
]
}
}
],
"logsBloom": "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000200000000000000000000000000028000000000000000002000000000000000000000010000000000000000004000000000000000000000000000000000000000000000000000000000100000000000000000000000000000000000000000000000000020000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000002000000000000000000000000000010000000000000000000000000040000000000000000000000000000800000",
"status": true,
"trace": [
{
"decodedInput": [
{
"name": "usr",
"type": "address",
"value": "0xf1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1"
},
{
"name": "wad",
"type": "uint256",
"value": "299"
}
],
"decodedOutput": [
{
"name": "",
"type": "bool",
"value": true
}
],
"from": "0xe2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2",
"gas": "0x79bdb0",
"gasUsed": "0x5fc2",
"input": "0x095ea7b3000000000000000000000000f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1000000000000000000000000000000000000000000000000000000000000012b",
"method": "approve",
"output": "0x0000000000000000000000000000000000000000000000000000000000000001",
"subtraces": 0,
"to": "0x6b175474e89094c44da98b954eedeac495271d0f",
"traceAddress": [0],
"type": "CALL",
"value": "0x0"
}
],
"type": "0x0"
}
}

Simulating with state overrides

The following example shows a simulation of an arbitrary sender 0xe2e2...e2 calling the mint function of the DAI Mainnet contract (0x6b17...71d0f).
In order to mint, the sender of the transaction must be a ward, which this address isn't. To simulate minting, we'll need to do a state override. Prior to running the simulation, the value overrides for the contract's storage slots will be applied to the current state of the contract.
When using Simulation RPC, state overrides are the third argument of the tenderly_simulateTransaction RPC call. To specify overrides, provide a map from the contract address to the overrides map. The overrides map takes the smart contract's storage location as keys and the value override as value.
For this example, we need to override the following:
wards['0xe2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2'] = 1
The value override must be supplied to the following storage location:
keccak256(0xf2...f2⏟sender, 20B . 0x00..00⏟wards slot, 32B){keccak_{256} \lparen \underbrace{\tt{0xf2...f2}}_\text{\tt{sender}, 20B}\ .\ \underbrace{\tt{0x00..00}}_\text{\tt{wards} slot, 32B}\rparen}
In our case, this evaluates to 0xedd7d04419e9c48ceb6055956cbb4e2091ae310313a4d1fa7cbcfe7561616e03 and the override map (the third argument) looks as follows:
{
"0x6b175474e89094c44da98b954eedeac495271d0f": {
"stateDiff": {
"0xedd7d04419e9c48ceb6055956cbb4e2091ae310313a4d1fa7cbcfe7561616e03": "0x0000000000000000000000000000000000000000000000000000000000000001"
}
}
}
Here's the cURL performing the request. Check out the Transfer event in the response.
Simulation RPC
Simulation RPC Response
# simulate DAI minting by 0xe2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2
# 0xf1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1 gets the minted DAI
# Simulated on the latest block
curl https://mainnet.gateway.tenderly.co/$TENDERLY_WEB3_GATEWAY_KEY \
-X POST \
-H "Content-Type: application/json" \
-d \
'{
"id": 0,
"jsonrpc": "2.0",
"method": "tenderly_simulateTransaction",
"params": [
{
"from": "0xe2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2",
"to": "0x6b175474e89094c44da98b954eedeac495271d0f",
"gas": "0x7a1200",
"data": "0x40c10f19000000000000000000000000f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f10000000000000000000000000000000000000000000000001bc16d674ec80000"
},
"latest",
{
"0x6b175474e89094c44da98b954eedeac495271d0f": {
"stateDiff": {
"0xedd7d04419e9c48ceb6055956cbb4e2091ae310313a4d1fa7cbcfe7561616e03": "0x0000000000000000000000000000000000000000000000000000000000000001"
}
}
}
]
}'
{
"id": 0,
"jsonrpc": "2.0",
"result": {
"blockNumber": "0xfd0dc8",
"cumulativeGasUsed": "0x0",
"gasUsed": "0xd0e5",
"logs": [
{
"anonymous": false,
"inputs": [
{
"name": "src",
"type": "address",
"value": "0x0000000000000000000000000000000000000000"
},
{
"name": "dst",
"type": "address",
"value": "0xf1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1"
},
{
"name": "wad",
"type": "uint256",
"value": "2000000000000000000"
}
],
"name": "Transfer",
"raw": {
"address": "0x6b175474e89094c44da98b954eedeac495271d0f",
"data": "0x0000000000000000000000000000000000000000000000001bc16d674ec80000",
"topics": [
"0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef",
"0x0000000000000000000000000000000000000000000000000000000000000000",
"0x000000000000000000000000f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1"
]
}
}
],
"logsBloom": "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000008000000000000000000000000000000000000000010000000020000000004000000000800000000000000000000000010000000000000000000000100000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000002000000000000000000000000000002000000000000000000000020000000000000000000000000000000040000000000000000000000000000000000",
"status": true,
"trace": [
{
"decodedInput": [
{
"name": "usr",
"type": "address",
"value": "0xf1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1"
},
{
"name": "wad",
"type": "uint256",
"value": "2000000000000000000"
}
],
"from": "0xe2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2",
"gas": "0x79bd80",
"gasUsed": "0x7c65",
"input": "0x40c10f19000000000000000000000000f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f1f10000000000000000000000000000000000000000000000001bc16d674ec80000",
"method": "mint",
"output": "0x",
"subtraces": 0,
"to": "0x6b175474e89094c44da98b954eedeac495271d0f",
"traceAddress": [0],
"type": "CALL",
"value": "0x0"
}
],
"type": "0x0"
}
}

Simulating a bundle of transactions

The custom tenderly_simulateBundle endpoint allows you to simulate several transactions by passing them as an array. The transactions are simulated as if they executed one after another in the same block.
The following code performs a simulation bundle of the following transactions:
  1. 1.
    Minting 2 DAI for e58b9ee93700a616b50509c8292977fa7a0f8ce1 (if you don't have any already). To achieve this, simulate a call to the mint function with a state override to the wards mapping, so the address 0xe2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2 becomes a ward for this simulation.
  2. 2.
    Now that e58b9ee93700a616b50509c8292977fa7a0f8ce1 has 2 DAI, we need a transaction that approves 1 DAI to f7ddedc66b1d482e5c38e4730b3357d32411e5dd.
  3. 3.
    A transaction where 0xf7ddedc66b1d482e5c38e4730b3357d32411e5dd calls transferFrom and sends to e58b9ee93700a616b50509c8292977fa7a0f8ce1.
Look for the Transfer, Approve, and Transfer events in the response, meaning the effects of prior transactions are visible to subsequent ones.
Simulation Bundle RPC
Simulation Bundle RPC Response
curl https://mainnet.gateway.tenderly.co/$TENDERLY_WEB3_GATEWAY_KEY \
-X POST \
-H "Content-Type: application/json" \
-d \
'{
"id": 0,
"jsonrpc": "2.0",
"method": "tenderly_simulateBundle",
"params": [
[
{
"from": "0xe2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2",
"to": "0x6b175474e89094c44da98b954eedeac495271d0f",
"data": "0x40c10f19000000000000000000000000e58b9ee93700a616b50509c8292977fa7a0f8ce10000000000000000000000000000000000000000000000001bc16d674ec80000"
},
{
"from": "0xe58b9ee93700a616b50509c8292977fa7a0f8ce1",
"to": "0x6b175474e89094c44da98b954eedeac495271d0f",
"gas": "0x7a1200",
"data": "0x095ea7b3000000000000000000000000f7ddedc66b1d482e5c38e4730b3357d32411e5dd0000000000000000000000000000000000000000000000000de0b6b3a7640000"
},
{
"from": "0xf7ddedc66b1d482e5c38e4730b3357d32411e5dd",
"to": "0x6b175474e89094c44da98b954eedeac495271d0f",
"gas": "0x7a1200",
"data": "0x23b872dd000000000000000000000000e58b9ee93700a616b50509c8292977fa7a0f8ce1000000000000000000000000bd8daa414fda8a8a129f7035e7496759c5af8570000000000000000000000000000000000000000000000000006a94d74f430000"
}
],
"latest",
{
"0x6b175474e89094c44da98b954eedeac495271d0f": {
"stateDiff": {
"0xedd7d04419e9c48ceb6055956cbb4e2091ae310313a4d1fa7cbcfe7561616e03": "0x0000000000000000000000000000000000000000000000000000000000000001"
}
}
}
]
}'
{
"id": 0,
"jsonrpc": "2.0",
"result": [
{
"blockNumber": "0xfd2eff",
"cumulativeGasUsed": "0x0",
"gasUsed": "0xd0d9",
"logs": [
{
"anonymous": false,
"inputs": [
{
"name": "src",
"type": "address",
"value": "0x0000000000000000000000000000000000000000"
},
{
"name": "dst",
"type": "address",
"value": "0xe58b9ee93700a616b50509c8292977fa7a0f8ce1"
},
{
"name": "wad",
"type": "uint256",
"value": "2000000000000000000"
}
],
"name": "Transfer",
"raw": {
"address": "0x6b175474e89094c44da98b954eedeac495271d0f",
"data": "0x0000000000000000000000000000000000000000000000001bc16d674ec80000",
"topics": [
"0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef",
"0x0000000000000000000000000000000000000000000000000000000000000000",
"0x000000000000000000000000e58b9ee93700a616b50509c8292977fa7a0f8ce1"
]
}
}
],
"logsBloom": "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000008000000000000000000000000000000000000000010000000020000000000000000000800000000000000000000000010000000000000000000004000800000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000002000000000000000000020000000002000000000000000000000020000000000000000000000000000000000000000000000000000000000000000000",
"status": true,
"trace": [
{
"decodedInput": [
{
"name": "usr",
"type": "address",
"value": "0xe58b9ee93700a616b50509c8292977fa7a0f8ce1"
},
{
"name": "wad",
"type": "uint256",
"value": "2000000000000000000"
}
],
"from": "0xe2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2e2",
"gas": "0x5f58c8c",
"gasUsed": "0x7c65",
"input": "0x40c10f19000000000000000000000000e58b9ee93700a616b50509c8292977fa7a0f8ce10000000000000000000000000000000000000000000000001bc16d674ec80000",
"method": "mint",
"output": "0x",
"subtraces": 0,
"to": "0x6b175474e89094c44da98b954eedeac495271d0f",
"traceAddress": [0],
"type": "CALL",
"value": "0x0"
}
],
"type": "0x0"
},
{
"blockNumber": "0xfd2eff",
"cumulativeGasUsed": "0x0",
"gasUsed": "0xb442",
"logs": [
{
"anonymous": false,
"inputs": [
{
"name": "src",
"type": "address",
"value": "0xe58b9ee93700a616b50509c8292977fa7a0f8ce1"
},
{
"name": "guy",
"type": "address",
"value": "0xf7ddedc66b1d482e5c38e4730b3357d32411e5dd"
},
{
"name": "wad",
"type": "uint256",
"value": "1000000000000000000"
}
],
"name": "Approval",
"raw": {
"address": "0x6b175474e89094c44da98b954eedeac495271d0f",
"data": "0x0000000000000000000000000000000000000000000000000de0b6b3a7640000",
"topics": [
"0x8c5be1e5ebec7d5bd14f71427d1e84f3dd0314c0f7b2291e5b200ac8c7c3b925",
"0x000000000000000000000000e58b9ee93700a616b50509c8292977fa7a0f8ce1",
"0x000000000000000000000000f7ddedc66b1d482e5c38e4730b3357d32411e5dd"
]
}
}
],
"logsBloom": "0x00000000000000000000000000000000000000000000000000000000000000002000000000000000000000000000000000000000000000000000000000200000000000000000000000000008000000000000000000000000000000000000000010000000000000000000020000000000000000000000000000000000000000000000000000004000800000000000000000000000000000000000000000000000020000000000000000000000000000000000000000000000000000000000000000000000000000000000000000020000000002000000000000000000000000100010000000000000000000000000000000000000000000000000000000000000",
"status": true,
"trace": [
{
"decodedInput": [
{
"name": "usr",
"type": "address",
"value": "0xf7ddedc66b1d482e5c38e4730b3357d32411e5dd"
},
{
"name": "wad",
"type": "uint256",
"value": "1000000000000000000"
}
],
"decodedOutput": [
{
"name": "",
"type": "bool",
"value": true
}
],
"from": "0xe58b9ee93700a616b50509c8292977fa7a0f8ce1",
"gas": "0x79bd80",
"gasUsed": "0x5fc2",
"input": "0x095ea7b3000000000000000000000000f7ddedc66b1d482e5c38e4730b3357d32411e5dd0000000000000000000000000000000000000000000000000de0b6b3a7640000",
"method": "approve",
"output": "0x0000000000000000000000000000000000000000000000000000000000000001",
"subtraces": 0,
"to": "0x6b175474e89094c44da98b954eedeac495271d0f",
"traceAddress": [0],
"type": "CALL",
"value": "0x0"
}
],
"type": "0x0"
},
{
"blockNumber": "0xfd2eff",
"cumulativeGasUsed": "0x0",
"gasUsed": "0xe38b",
"logs": [
{
"anonymous": false,
"inputs": [
{
"name": "src",
"type": "address",
"value": "0xe58b9ee93700a616b50509c8292977fa7a0f8ce1"
},
{
"name": "dst",
"type": "address",
"value": "0xbd8daa414fda8a8a129f7035e7496759c5af8570"
},
{
"name": "wad",
"type": "uint256",
"value": "30000000000000000"
}
],
"name": "Transfer",
"raw": {
"address": "0x6b175474e89094c44da98b954eedeac495271d0f",
"data": "0x000000000000000000000000000000000000000000000000006a94d74f430000",
"topics": [
"0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef",
"0x000000000000000000000000e58b9ee93700a616b50509c8292977fa7a0f8ce1",
"0x000000000000000000000000bd8daa414fda8a8a129f7035e7496759c5af8570"
]
}
}
],
"logsBloom": "0x00000000000000800000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000008000000000000000000000000000000000000000010000000000000000000000000000000000000000000000000000010000000000000000000004000800000000000000000000000000000000000000000000000000000000000000000000000000000000000000000040000000000000000000000000002000000000000000000020000000002000000000000000000000000000000000000000000000000004000000000000000000000000000000000000000",
"status": true,
"trace": [
{
"decodedInput": [
{
"name": "src",
"type": "address",
"value": "0xe58b9ee93700a616b50509c8292977fa7a0f8ce1"
},
{
"name": "dst",
"type": "address",
"value": "0xbd8daa414fda8a8a129f7035e7496759c5af8570"
},
{
"name": "wad",
"type": "uint256",
"value": "30000000000000000"
}
],
"decodedOutput": [
{
"name": "",
"type": "bool",
"value": true
}
],
"from": "0xf7ddedc66b1d482e5c38e4730b3357d32411e5dd",
"gas": "0x79bc28",
"gasUsed": "0x8db3",
"input": "0x23b872dd000000000000000000000000e58b9ee93700a616b50509c8292977fa7a0f8ce1000000000000000000000000bd8daa414fda8a8a129f7035e7496759c5af8570000000000000000000000000000000000000000000000000006a94d74f430000",
"method": "transferFrom",
"output": "0x0000000000000000000000000000000000000000000000000000000000000001",
"subtraces": 0,
"to": "0x6b175474e89094c44da98b954eedeac495271d0f",
"traceAddress": [0],
"type": "CALL",
"value": "0x0"
}
],
"type": "0x0"
}
]
}