> ## Documentation Index > Fetch the complete documentation index at: https://docs.tenderly.co/llms.txt > Use this file to discover all available pages before exploring further. # Simulate Bundles > Simulate a bundle of transactions and get exact gas estimates with the tenderly_simulateBundle and tenderly_estimateGasBundle JSON-RPC methods. The custom RPC methods appear in the **`tenderly_`** namespace. Two methods execute a sequence of transactions against a given block without sending them on chain. Each transaction in the bundle executes on the state left by the previous one: * [`tenderly_simulateBundle`](#tenderly_simulatebundle) returns the full decoded execution result for every transaction: logs, call trace, asset changes, and balance changes. * [`tenderly_estimateGasBundle`](#tenderly_estimategasbundle) executes the bundle the same way but returns only gas figures per transaction. Use it when you need exact gas values without the full simulation payload. ### `tenderly_simulateBundle` Simulates a bundle of transactions as it would execute on the given block and returns results for each transaction. **Params** 1. **Transactions** Transactions `ARRAY`: list of transactions in a bundle * **from** (*optional*) `STRING`: hex encoded address * **to** `STRING`: hex encoded address * **gas** (*optional*) `NUMBER` * **maxFeePerGas** (*optional*) `NUMBER` max fee: The maximum total fee per gas the sender is willing to pay (includes the network / base fee and miner / priority fee) in wei * **maxPriorityFeePerGas** (*optional*) `NUMBER` max priority fee: Maximum fee per gas the sender is willing to pay to miners in wei * **gasPrice** (*optional*) `NUMBER`: The gas price willing to be paid by the sender in wei * **value** (*optional*) `NUMBER` * **data** (*optional*) `STRING`: hex encoded bytes * **accessList** (*optional*) `ARRAY` of Access list entry `OBJECT` * **address** `STRING` hex encoded address * **storageKeys** `ARRAY` of `STRING` representation of 32 byte hex encoded storage key 2. **Simulation Block Number** (*optional*) The block number against which transaction should be simulated. Either: * `STRING` Block number * `ENUM` of Block tag `earliest|finalized|safe|latest|pending` 3. **State Overrides** (*optional*) `MAP`: mapping from an account (address) to override specification * **key** `STRING`: the account this override applies to * **value** `OBJECT`: the override specification * **nonce** (*optional*) `STRING`: hex encoded 8 byte nonce override for the account * **code** (*optional*) `STRING`: data of the code override for the account * **balance** (*optional*) `STRING`: hex encoded 32 byte balance override for the account in wei * **stateDiff** (*optional*) `MAP`: mapping of storage key to storage value override * **key** `STRING`: the storage key * **value** `STRING`: the value override for the given storage key 4. **Block Overrides** (optional) `OBJECT`: The set of header fields to override in a block. * **number** *(optional)* `STRING`: hex, overrides the block number * **difficulty** *(optional)* `STRING`: hex, overrides the block difficulty * **time** (*optional*) `STRING`: hex, overrides block timestamp * **gasLimit** *(optional)* `STRING`: hex, overrides gas limit * **coinbase** *(optional)* `STRING`: hex, overrides block miner * **random** *(optional)* `STRING`: hex, overrides the blocks extra data which feeds into the RANDOM opcode * **baseFee** *(optional)* `STRING`: hex, overrides block base fee **Example** ```json title="example.json" showLineNumbers theme={"theme":{"light":"catppuccin-latte","dark":"catppuccin-mocha"}} { "id": 0, "jsonrpc": "2.0", "method": "tenderly_simulateBundle", "params": [ [ { "from": "0xd8da6bf26964af9d7eed9e03e53415d37aa96045", "to": "0xc02aaa39b223fe8d0a0e5c4f27ead9083c756cc2", "data": "0x095ea7b300000000000000000000000020a5814b73ef3537c6e099a0d45c798f4bd6e1d60000000000000000000000000000000000000000000000000000000000000001" }, { "from": "0x20a5814b73ef3537c6e099a0d45c798f4bd6e1d6", "to": "0xc02aaa39b223fe8d0a0e5c4f27ead9083c756cc2", "data": "0x23b872dd000000000000000000000000d8da6bf26964af9d7eed9e03e53415d37aa9604500000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001" } ], "0xF4D880" ] } ``` ```bash title="example" showLineNumbers theme={"theme":{"light":"catppuccin-latte","dark":"catppuccin-mocha"}} curl https://mainnet.gateway.tenderly.co/$TENDERLY_NODE_ACCESS_KEY \ -X POST \ -H "Content-Type: application/json" \ -d \ '{ "id": 0, "jsonrpc": "2.0", "method": "tenderly_simulateBundle", "params": [ [ { "from": "0xd8da6bf26964af9d7eed9e03e53415d37aa96045", "to": "0xc02aaa39b223fe8d0a0e5c4f27ead9083c756cc2", "data": "0x095ea7b300000000000000000000000020a5814b73ef3537c6e099a0d45c798f4bd6e1d60000000000000000000000000000000000000000000000000000000000000001" }, { "from": "0x20a5814b73ef3537c6e099a0d45c798f4bd6e1d6", "to": "0xc02aaa39b223fe8d0a0e5c4f27ead9083c756cc2", "data": "0x23b872dd000000000000000000000000d8da6bf26964af9d7eed9e03e53415d37aa9604500000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001" } ], "0xF4D880" ] }' ``` ```javascript title="example.js" showLineNumbers theme={"theme":{"light":"catppuccin-latte","dark":"catppuccin-mocha"}} // Installation Instructions: https://docs.ethers.io/v5/getting-started/#installing const { ethers } = require("ethers"); async function runSimulateTransaction() { // Initialize an ethers instance const provider = new ethers.providers.JsonRpcProvider( "https://goerli.gateway.tenderly.co/$TENDERLY_WEB3_GATEWAY_KEY" ); // Execute method const result = await provider.send("tenderly_simulateBundle", [ [ { "from": "0xd8da6bf26964af9d7eed9e03e53415d37aa96045", "to": "0xc02aaa39b223fe8d0a0e5c4f27ead9083c756cc2", "data": "0x095ea7b300000000000000000000000020a5814b73ef3537c6e099a0d45c798f4bd6e1d60000000000000000000000000000000000000000000000000000000000000001" }, { "from": "0x20a5814b73ef3537c6e099a0d45c798f4bd6e1d6", "to": "0xc02aaa39b223fe8d0a0e5c4f27ead9083c756cc2", "data": "0x23b872dd000000000000000000000000d8da6bf26964af9d7eed9e03e53415d37aa9604500000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001" } ], "0xF4D880", ]); // Print the output to console console.log(result); } (async () => { runSimulateTransaction(); })(); ``` ```json title="example.json" showLineNumbers theme={"theme":{"light":"catppuccin-latte","dark":"catppuccin-mocha"}} { "id": 0, "jsonrpc": "2.0", "result": [ { "status": true, "gasUsed": "0xb3a8", "cumulativeGasUsed": "0x0", "blockNumber": "0xf4d881", "type": "0x0", "logsBloom": "0x00000000000000000000000000000000000000000000000000000000000000000000000000800000000000000000000002000000080000000000000000200000000000000000000000000000000000000000000000000000000008000000000000000000000000000000000000000000000000000000000000000000000000000000004000000000000000000000000080000000000000000000000000000000020000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000020000000000000000000000000000000010200000800000000000000000000000000000000000000000000000000000", "logs": [ { "name": "Approval", "anonymous": false, "inputs": [ { "value": "0xd8da6bf26964af9d7eed9e03e53415d37aa96045", "type": "address", "name": "src" }, { "value": "0x20a5814b73ef3537c6e099a0d45c798f4bd6e1d6", "type": "address", "name": "guy" }, { "value": "1", "type": "uint256", "name": "wad" } ], "raw": { "address": "0xc02aaa39b223fe8d0a0e5c4f27ead9083c756cc2", "topics": [ "0x8c5be1e5ebec7d5bd14f71427d1e84f3dd0314c0f7b2291e5b200ac8c7c3b925", "0x000000000000000000000000d8da6bf26964af9d7eed9e03e53415d37aa96045", "0x00000000000000000000000020a5814b73ef3537c6e099a0d45c798f4bd6e1d6" ], "data": "0x0000000000000000000000000000000000000000000000000000000000000001" } } ], "trace": [ { "type": "CALL", "from": "0xd8da6bf26964af9d7eed9e03e53415d37aa96045", "to": "0xc02aaa39b223fe8d0a0e5c4f27ead9083c756cc2", "gas": "0x5f58cbc", "gasUsed": "0x5f64", "value": "0x0", "input": "0x095ea7b300000000000000000000000020a5814b73ef3537c6e099a0d45c798f4bd6e1d60000000000000000000000000000000000000000000000000000000000000001", "decodedInput": [ { "value": "0x20a5814b73ef3537c6e099a0d45c798f4bd6e1d6", "type": "address", "name": "guy" }, { "value": "1", "type": "uint256", "name": "wad" } ], "method": "approve", "output": "0x0000000000000000000000000000000000000000000000000000000000000001", "decodedOutput": [ { "value": true, "type": "bool", "name": "" } ], "subtraces": 0, "traceAddress": [ 0 ] } ] }, { "status": true, "gasUsed": "0x8a78", "cumulativeGasUsed": "0x0", "blockNumber": "0xf4d881", "type": "0x0", "logsBloom": "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000002000000080000000000000000000000000000000000000000000008000000000000000000000000000000000000000000000000020000000000000000000800000000000000000000000010000000000000004000000000000000000000000080000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000002000000000000000000000000000000000000000000000000000020000000200000800000000000000000000000000000000000000000000000000000", "logs": [ { "name": "Transfer", "anonymous": false, "inputs": [ { "value": "0xd8da6bf26964af9d7eed9e03e53415d37aa96045", "type": "address", "name": "src" }, { "value": "0x0000000000000000000000000000000000000000", "type": "address", "name": "dst" }, { "value": "1", "type": "uint256", "name": "wad" } ], "raw": { "address": "0xc02aaa39b223fe8d0a0e5c4f27ead9083c756cc2", "topics": [ "0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef", "0x000000000000000000000000d8da6bf26964af9d7eed9e03e53415d37aa96045", "0x0000000000000000000000000000000000000000000000000000000000000000" ], "data": "0x0000000000000000000000000000000000000000000000000000000000000001" } } ], "trace": [ { "type": "CALL", "from": "0x20a5814b73ef3537c6e099a0d45c798f4bd6e1d6", "to": "0xc02aaa39b223fe8d0a0e5c4f27ead9083c756cc2", "gas": "0x5f58c3c", "gasUsed": "0x4874", "value": "0x0", "input": "0x23b872dd000000000000000000000000d8da6bf26964af9d7eed9e03e53415d37aa9604500000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001", "decodedInput": [ { "value": "0xd8da6bf26964af9d7eed9e03e53415d37aa96045", "type": "address", "name": "src" }, { "value": "0x0000000000000000000000000000000000000000", "type": "address", "name": "dst" }, { "value": "1", "type": "uint256", "name": "wad" } ], "method": "transferFrom", "output": "0x0000000000000000000000000000000000000000000000000000000000000001", "decodedOutput": [ { "value": true, "type": "bool", "name": "" } ], "subtraces": 0, "traceAddress": [ 0 ] } ] } ] } ``` **Result** Simulations result `ARRAY`: list of simulation results in a bundle * **status** `NUMBER:` either `1` (success) or `0` (failure) * **gasUsed** `NUMBER`: The amount of gas used by this specific transaction alone * **cumulativeGasUsed** `NUMBER`: the total amount of gas used when this transaction was executed in the block * **blockNumber** `NUMBER`: the block number in which this transaction was simulated * **type** `NUMBER`: transaction type, `0x00` for legacy transactions, `0x01` for access list types, `0x02` for dynamic fees * **logsBloom** `STRING`: bloom filter for light clients to quickly retrieve related logs * **logs**: an array of emitted events `ARRAY` of `OBJECT` * **name** `STRING`: event name * **anonymous** `BOOLEAN`: indicates if event is anonymous * **inputs**: array of decoded log arguments `ARRAY` of decoded logs `OBJECT` * **name** `STRING`: event argument name * **type** `STRING`: event argument type from Solidity type system * **value** (*optional*) `STRING` string representation value of the argument; interpret according to the `type` field * **raw** `OBJECT`: raw logs * **address** `STRING` hex encoded address: address of the contract emitting the log * **topics** `ARRAY` of `STRING` 32 hex encoded bytes * **data** `STRING` hex encoded string representing event data * **trace**: Trace `ARRAY` of `OBJECT` * **type** `STRING` type: trace item type - either `CALL`| `CALLCODE`| `STATICCALL`| `DELEGATECALL`| `CREATE`| `CREATE2`| `SELFDESTRUCT` * **from** `STRING`: hex encoded address * **to** `STRING`: hex encoded address * **gas** `STRING`: hex encoded unsigned 64 byte integer representing event gas * **gasUsed** `STRING`: hex encoded unsigned 64 byte integer representing event gasUsed * **value** `STRING`: hex encoded unsigned 64 byte integer representing event value in wei * **error** `STRING`: low-level error from virtual machine * **errorReason** `STRING`: extracted error reason in case of revert * **input** `STRING`: hex encoded string representation of raw input bytes for the trace point * **method** `STRING`: invoked contract method * **decodedInput** : decoded input for the invoked method - `ARRAY` of decoded in argument `OBJECT` * **value** `STRING`: string representation value of the argument; interpret according to the `type` field. * **type** `STRING`: the Solidity type of this argument * **name** `STRING`: the name of this argument * **output** `STRING`: raw trace output * **decodedOutput** : decoded output of the invoked method - `ARRAY` of decoded out argument `OBJECT` * **value** `STRING`: string representation value of the argument; interpret according to the `type` field. * **type** `STRING`: the Solidity type of this argument * **name** `STRING`: the name of this argument * **subtraces** `NUMBER`: number of child traces * **traceAddress** : trace position `ARRAY` of `NUMBER` * **`assetChanges`** `ARRAY`: * **`type`** `STRING` type of asset change, can be transfer, mint, burn * **`from`** `STRING`: address of the sender (empty for mint transfers) * **`to`** `STRING`: address of the receiver (empty for burn transfers) * **`amount`** `STRING`: the amount of the token that was transferred * **`rawAmount`** `STRING`: raw amount transfer for the token * **`dollarValue`**`STRING`: dollar value of the transferred token * **`assetInfo`**`OBJECT`: asset information * **`standard`** `STRING`: supported token standards: ERC20, ERC721, NativeCurrency * **`type`** `STRING`: the token type: Native, Fungible, Non-Fungible * **`contractAddress`**`STRING` : address of the contract * **`symbol`** `STRING`: token symbol * **`name`** `STRING`: token name * **`logo`** `STRING`: URL for the token icon * **`decimals`** `NUMBER`: number of decimals in the token * **`dollarValue`**`STRING`: dollar value of a single token * **`balanceChanges`** `ARRAY`: an array of balance changes - cumulated asset changes * **`address`** `STRING` address * **`dollarValue`** `STRING`: dollar value of cumulated asset changes * **`transfers`** `ARRAY`: array of asset changes indexes ### `tenderly_estimateGasBundle` Calculates exact gas estimates for the given list of transactions, with optional simulation-style state and block overrides. Like [`tenderly_estimateGas`](/node-rpc/guides/simulate-json-rpc#tenderly_estimategas), each estimate is based on a fully executed transaction, so the returned values are accurate where `eth_estimateGas` might revert and yield an underestimation. Transactions execute in order, each on the state left by the previous one. **Differences from `tenderly_simulateBundle`:** * Both methods execute the bundle the same way against the given block, and both accept the same state and block overrides. * `tenderly_simulateBundle` returns the full decoded execution result for every transaction: logs, call trace, asset changes, and balance changes. * `tenderly_estimateGasBundle` returns only two gas figures per transaction: the recommended gas limit and the gas actually consumed. Use it when you only need gas values; use `tenderly_simulateBundle` when you need to preview the bundle's effects. **Params** 1. **Transactions** Transactions `ARRAY`: list of transactions in a bundle, same shape as in [`tenderly_simulateBundle`](#tenderly_simulatebundle) 2. **Simulation Block Number** (*optional*) The block number against which the bundle should be executed. Either: * `STRING` Block number * `ENUM` of Block tag `earliest|finalized|safe|latest|pending` 3. **State Overrides** (*optional*) `MAP`: mapping from an account (address) to override specification, same shape as in [`tenderly_simulateBundle`](#tenderly_simulatebundle) 4. **Block Overrides** (*optional*) `OBJECT`: the set of header fields to override in a block, same shape as in [`tenderly_simulateBundle`](#tenderly_simulatebundle) **Example** ```json title="example.json" showLineNumbers theme={"theme":{"light":"catppuccin-latte","dark":"catppuccin-mocha"}} { "id": 0, "jsonrpc": "2.0", "method": "tenderly_estimateGasBundle", "params": [ [ { "from": "0x7f39C581F595B53c5cb19bD0b3f8dA6c935E2Ca0", "to": "0xae7ab96520DE3A18E5e111B5EaAb095312D7fE84", "data": "0x095ea7b30000000000000000000000009008d19f58aabd9ed0d60971565aa8510560ab410000000000000000000000000000000000000000000000000c1291a92f17a100" }, { "from": "0x9008D19f58AAbD9eD0D60971565AA8510560ab41", "to": "0xae7ab96520DE3A18E5e111B5EaAb095312D7fE84", "data": "0x23b872dd0000000000000000000000007f39c581f595b53c5cb19bd0b3f8da6c935e2ca00000000000000000000000009008d19f58aabd9ed0d60971565aa8510560ab410000000000000000000000000000000000000000000000000c1291a92f17a100" }, { "from": "0x9008D19f58AAbD9eD0D60971565AA8510560ab41", "to": "0xae7ab96520DE3A18E5e111B5EaAb095312D7fE84", "data": "0x095ea7b30000000000000000000000007f39c581f595b53c5cb19bd0b3f8da6c935e2ca00000000000000000000000000000000000000000000000000c1291a92f17a100" }, { "from": "0x9008D19f58AAbD9eD0D60971565AA8510560ab41", "to": "0x7f39C581F595B53c5cb19bD0b3f8dA6c935E2Ca0", "data": "0xea598cb00000000000000000000000000000000000000000000000000c1291a92f17a100" } ], "latest" ] } ``` ```bash title="example" showLineNumbers theme={"theme":{"light":"catppuccin-latte","dark":"catppuccin-mocha"}} curl https://mainnet.gateway.tenderly.co/$TENDERLY_NODE_ACCESS_KEY \ -X POST \ -H "Content-Type: application/json" \ -d \ '{ "id": 0, "jsonrpc": "2.0", "method": "tenderly_estimateGasBundle", "params": [ [ { "from": "0x7f39C581F595B53c5cb19bD0b3f8dA6c935E2Ca0", "to": "0xae7ab96520DE3A18E5e111B5EaAb095312D7fE84", "data": "0x095ea7b30000000000000000000000009008d19f58aabd9ed0d60971565aa8510560ab410000000000000000000000000000000000000000000000000c1291a92f17a100" }, { "from": "0x9008D19f58AAbD9eD0D60971565AA8510560ab41", "to": "0xae7ab96520DE3A18E5e111B5EaAb095312D7fE84", "data": "0x23b872dd0000000000000000000000007f39c581f595b53c5cb19bd0b3f8da6c935e2ca00000000000000000000000009008d19f58aabd9ed0d60971565aa8510560ab410000000000000000000000000000000000000000000000000c1291a92f17a100" }, { "from": "0x9008D19f58AAbD9eD0D60971565AA8510560ab41", "to": "0xae7ab96520DE3A18E5e111B5EaAb095312D7fE84", "data": "0x095ea7b30000000000000000000000007f39c581f595b53c5cb19bd0b3f8da6c935e2ca00000000000000000000000000000000000000000000000000c1291a92f17a100" }, { "from": "0x9008D19f58AAbD9eD0D60971565AA8510560ab41", "to": "0x7f39C581F595B53c5cb19bD0b3f8dA6c935E2Ca0", "data": "0xea598cb00000000000000000000000000000000000000000000000000c1291a92f17a100" } ], "latest" ] }' ``` ```json title="response.json" showLineNumbers theme={"theme":{"light":"catppuccin-latte","dark":"catppuccin-mocha"}} { "id": 0, "jsonrpc": "2.0", "result": [ { "gas": "0x12579", "gasUsed": "0xff06" }, { "gas": "0x10918", "gasUsed": "0xb551" }, { "gas": "0xa621", "gasUsed": "0x6625" }, { "gas": "0x10649", "gasUsed": "0xb249" } ] } ``` **Result** Gas estimates `ARRAY`: list of gas estimates, one per transaction in the bundle * **gas** `STRING`: hex-encoded recommended gas limit to set on the transaction (includes a safety margin over the gas actually consumed) * **gasUsed** `STRING`: hex-encoded amount of gas actually consumed by the executed transaction