eth_simulateV1

Simulates one or more transaction bundles against the current pre-confirmed Flashblock state. Only available on Flashblocks endpoints.

Simulates one or more transaction bundles against the current pre-confirmed Flashblock state. Supports state overrides, multi-block simulation, and optional transfer tracing.

Only available on Flashblocks endpoints: https://mainnet.base.org / https://sepolia.base.org.

Parameters

simulationPayload · object · required

The simulation configuration.

Show Simulation payload fields

blockStateCalls · array · required

Array of block state call objects. Each object represents one simulated block.

Show Block state call fields

calls · array

Array of transaction call objects to simulate within this block.

stateOverrides · object

Per-address state overrides applied before simulation (e.g., balance, nonce, code, storage). Optional.

blockOverrides · object

Block-level overrides (e.g., number, timestamp). Optional.

traceTransfers · boolean

If true, ETH transfer events are included as logs in the result. Defaults to false.

validation · boolean

If true, transaction validation (nonce, balance) is enforced. Defaults to false.

blockParameter · string · required

Use "pending" to simulate against the current Flashblock state.

Returns

result · array

Array of simulated block results, one per entry in blockStateCalls. Each entry is a full block object with a calls field embedded alongside standard block fields.

Show Block result fields

number · string

Simulated block number (hex).

hash · string

Simulated block hash.

parentHash · string

Parent block hash.

timestamp · string

Block timestamp (hex).

gasLimit · string

Gas limit (hex).

gasUsed · string

Total gas used by the simulated calls (hex).

baseFeePerGas · string

Base fee per gas (hex).

stateRoot · string

Always "0x000...000" — simulation does not commit state to the trie.

calls · array

Array of individual call results.

Show Call result fields

status · string

"0x1" for success, "0x0" for failure.

gasUsed · string

Gas used as a hexadecimal integer.

returnData · string

Hex-encoded return data.

logs · array

Logs emitted (including ETH transfer logs if traceTransfers is true).

error · string

Revert reason if the call failed. Optional.

Example

cURL

curl https://sepolia.base.org \
  -X POST \
  -H "Content-Type: application/json" \
  -d '{
    "jsonrpc": "2.0",
    "method": "eth_simulateV1",
    "params": [
      {
        "blockStateCalls": [
          {
            "calls": [{"to": "0x...", "data": "0x..."}],
            "stateOverrides": {}
          }
        ],
        "traceTransfers": true,
        "validation": true
      },
      "pending"
    ],
    "id": 1
  }'

{
  "jsonrpc": "2.0",
  "id": 1,
  "result": [
    {
      "baseFeePerGas": "0x0",
      "blobGasUsed": "0x39d0",
      "calls": [
        {
          "gasUsed": "0x5208",
          "logs": [],
          "returnData": "0x",
          "status": "0x1"
        }
      ],
      "difficulty": "0x0",
      "excessBlobGas": "0x0",
      "extraData": "0x01000000640000000500000000004c4b40",
      "gasLimit": "0x17d78400",
      "gasUsed": "0x5208",
      "hash": "0x2f2f692821995e39653f63164b2d5d0e0bba66c86c2a199fd3009c0b9906c7b0",
      "logsBloom": "0x000...000",
      "miner": "0x4200000000000000000000000000000000000011",
      "mixHash": "0x0000000000000000000000000000000000000000000000000000000000000000",
      "nonce": "0x0000000000000000",
      "number": "0x2c31c49",
      "parentBeaconBlockRoot": "0x64e625f8bc74f78539f962aa09d522c63576ff6ad57170c668882d99e669ef52",
      "parentHash": "0x9653660afa4fca3976a21d42ebf849c337e9840993f050fee3affc673a573bf8",
      "receiptsRoot": "0xf78dfb743fbd92ade140711c8bbc542b5e307f0ab7984eff35d751969fe57efa",
      "requestsHash": "0xe3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855",
      "sha3Uncles": "0x1dcc4de8dec75d7aab85b567b6ccd41ad312451b948a7413f0a142fd40d49347",
      "size": "0x2a6",
      "stateRoot": "0x0000000000000000000000000000000000000000000000000000000000000000",
      "timestamp": "0x6a10957f",
      "transactions": [
        "0xa401668a06b038c488c1abc013676dfe63fc645d182ece34d8b3f40f45689279"
      ],
      "transactionsRoot": "0x0b1328c457d7a8108ea9f2559142890491b680fdb691720b3d0c857c3d11002c",
      "uncles": [],
      "withdrawals": [],
      "withdrawalsRoot": "0x0000000000000000000000000000000000000000000000000000000000000000"
    }
  ]
}