# simulateContract \[Simulates & validates a contract interaction.] The `simulateContract` function **simulates**/**validates** a contract interaction. This is useful for retrieving **return data** and **revert reasons** of contract write functions. This function does not require gas to execute and ***does not*** change the state of the blockchain. It is almost identical to [`readContract`](/docs/contract/readContract), but also supports contract write functions. Internally, `simulateContract` uses a [Public Client](/docs/clients/public) to call the [`call` action](/docs/actions/public/call) with [ABI-encoded `data`](/docs/contract/encodeFunctionData). ## Usage Below is a very basic example of how to simulate a write function on a contract (with no arguments). The `mint` function accepts no arguments, and returns a token ID. :::code-group ```ts [example.ts] import { account, publicClient } from './config' import { wagmiAbi } from './abi' const { result } = await publicClient.simulateContract({ address: '0xFBA3912Ca04dd458c843e2EE08967fC04f3579c2', abi: wagmiAbi, functionName: 'mint', account, }) ``` ```ts [abi.ts] export const wagmiAbi = [ ... { inputs: [], name: "mint", outputs: [{ name: "", type: "uint32" }], stateMutability: "view", type: "function", }, ... ] as const; ``` ```ts [config.ts] import { createPublicClient, http } from 'viem' import { privateKeyToAccount } from 'viem/accounts' import { mainnet } from 'viem/chains' // JSON-RPC Account export const account = '0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266' // Local Account export const account = privateKeyToAccount(...) export const publicClient = createPublicClient({ chain: mainnet, transport: http() }) ``` ::: ### Passing Arguments If your function requires argument(s), you can pass them through with the `args` attribute. TypeScript types for `args` will be inferred from the function name & ABI, to guard you from inserting the wrong values. For example, the `mint` function name below requires a **tokenId** argument, and it is typed as `[number]`. :::code-group ```ts [example.ts] import { account, publicClient } from './config' import { wagmiAbi } from './abi' const { result } = await publicClient.simulateContract({ address: '0xFBA3912Ca04dd458c843e2EE08967fC04f3579c2', abi: wagmiAbi, functionName: 'mint', args: [69420], // [!code focus] account, }) ``` ```ts [abi.ts] export const wagmiAbi = [ ... { inputs: [{ name: "owner", type: "uint32" }], name: "mint", outputs: [{ name: "", type: "uint32" }], stateMutability: "view", type: "function", }, ... ] as const; ``` ```ts [config.ts] import { createPublicClient, http } from 'viem' import { privateKeyToAccount } from 'viem/accounts' import { mainnet } from 'viem/chains' // JSON-RPC Account export const account = '0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266' // Local Account export const account = privateKeyToAccount(...) export const publicClient = createPublicClient({ chain: mainnet, transport: http() }) ``` ::: ### Pairing with `writeContract` The `simulateContract` function also pairs well with `writeContract`. In the example below, we are **validating** if the contract write will be successful via `simulateContract`. If no errors are thrown, then we are all good. After that, we perform a contract write to execute the transaction. :::code-group ```ts [example.ts] import { account, walletClient, publicClient } from './config' import { wagmiAbi } from './abi' const { request } = await publicClient.simulateContract({ address: '0xFBA3912Ca04dd458c843e2EE08967fC04f3579c2', abi: wagmiAbi, functionName: 'mint', account, }) const hash = await walletClient.writeContract(request) ``` ```ts [abi.ts] export const wagmiAbi = [ ... { inputs: [], name: "mint", outputs: [{ name: "", type: "uint32" }], stateMutability: "view", type: "function", }, ... ] as const; ``` ```ts [config.ts] import { createPublicClient, custom, http } from 'viem' import { privateKeyToAccount } from 'viem/accounts' import { mainnet } from 'viem/chains' // JSON-RPC Account export const account = '0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266' // Local Account export const account = privateKeyToAccount(...) export const walletClient = createWalletClient({ chain: mainnet, transport: custom(window.ethereum) }) export const publicClient = createPublicClient({ chain: mainnet, transport: http() }) ``` ::: ### Handling Custom Errors In the example below, we are **catching** a [custom error](https://blog.soliditylang.org/2021/04/21/custom-errors/) thrown by the `simulateContract`. It is important to include the custom error item in the contract `abi`. You can access the custom error through the `data` attribute of the error: :::code-group ```ts [example.ts] {13-27} import { BaseError, ContractFunctionRevertedError } from 'viem'; import { account, walletClient, publicClient } from './config' import { wagmiAbi } from './abi' try { await publicClient.simulateContract({ address: '0xFBA3912Ca04dd458c843e2EE08967fC04f3579c2', abi: wagmiAbi, functionName: 'mint', account, }) } catch (err) { if (err instanceof BaseError) { const revertError = err.walk(err => err instanceof ContractFunctionRevertedError) if (revertError instanceof ContractFunctionRevertedError) { const errorName = revertError.data?.errorName ?? '' // do something with `errorName` } } } ``` ```ts [abi.ts] export const wagmiAbi = [ ... { inputs: [], name: "mint", outputs: [{ name: "", type: "uint32" }], stateMutability: "view", type: "function", }, // Custom solidity error { type: 'error', inputs: [], name: 'MintIsDisabled' }, ... ] as const; ``` ```solidity [WagmiExample.sol] // ... error MintIsDisabled(); contract WagmiExample { // ... function mint() public { // ... revert MintIsDisabled(); // ... } // ... } ``` ```ts [config.ts] import { createPublicClient, custom, http } from 'viem' import { privateKeyToAccount } from 'viem/accounts' import { mainnet } from 'viem/chains' // JSON-RPC Account export const account = '0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266' // Local Account export const account = privateKeyToAccount(...) export const walletClient = createWalletClient({ chain: mainnet, transport: custom(window.ethereum) }) export const publicClient = createPublicClient({ chain: mainnet, transport: http() }) ``` ::: ### State Overrides When using `simulateContract`, there sometimes needs to be an initial state change to make the transaction pass. A common use case would be an approval. For that, there are [state overrides](https://geth.ethereum.org/docs/interacting-with-geth/rpc/ns-eth#eth-call). In the example below, we are simulating sending a token on behalf of another user. To do this, we need to modify the state of the token contract to have maximum approve from the token owner. :::code-group ```ts twoslash [example.ts] // @twoslash-cache: 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"} import { account, publicClient } from './config' import { abi, address } from './contract' // Allowance slot: A 32 bytes hex string representing the allowance slot of the sender. const allowanceSlot = '0x....' // Max allowance: A 32 bytes hex string representing the maximum allowance (2^256 - 1) const maxAllowance = numberToHex(maxUint256) const { result } = await publicClient.simulateContract({ abi, address, account, functionName: 'transferFrom', args: [ '0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266', account.address, 69420n ], stateOverride: [ // [!code hl] { // [!code hl] // modifying the state of the token contract // [!code hl] address, // [!code hl] stateDiff: [ // [!code hl] { // [!code hl] slot: allowanceSlot, // [!code hl] value: maxAllowance, // [!code hl] }, // [!code hl] ], // [!code hl] }, // [!code hl] ], // [!code hl] }) console.log(result) // @log: Output: true ``` ```ts twoslash [contract.ts] filename="contract.ts" // @twoslash-cache: 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export const address = '0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48' export const abi = [ { type: 'function', name: 'transferFrom', stateMutability: 'nonpayable', inputs: [ { name: 'sender', type: 'address', }, { name: 'recipient', type: 'address', }, { name: 'amount', type: 'uint256', }, ], outputs: [ { type: 'bool', }, ], }, ] as const ``` ```ts twoslash [config.ts] filename="config.ts" // @twoslash-cache: 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import { createPublicClient, custom, http } from 'viem' import { privateKeyToAccount } from 'viem/accounts' import { mainnet } from 'viem/chains' export const account = privateKeyToAccount('0x...') export const publicClient = createPublicClient({ chain: mainnet, transport: http() }) ``` ::: ## Return Value The simulation result and write request. Type is inferred. ## Parameters ### address * **Type:** [`Address`](/docs/glossary/types#address) The contract address. ```ts const { result } = await publicClient.simulateContract({ address: '0xFBA3912Ca04dd458c843e2EE08967fC04f3579c2', // [!code focus] abi: wagmiAbi, functionName: 'mint', account: '0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266' }) ``` ### abi * **Type:** [`Abi`](/docs/glossary/types#abi) The contract's ABI. ```ts const { result } = await publicClient.simulateContract({ address: '0xFBA3912Ca04dd458c843e2EE08967fC04f3579c2', abi: wagmiAbi, // [!code focus] functionName: 'mint', account: '0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266' }) ``` ### functionName * **Type:** `string` A function to extract from the ABI. ```ts const { result } = await publicClient.simulateContract({ address: '0xFBA3912Ca04dd458c843e2EE08967fC04f3579c2', abi: wagmiAbi, functionName: 'mint', // [!code focus] account: '0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266' }) ``` ### account * **Type:** `Account | Address | null` The Account to simulate the contract method from. Accepts a [JSON-RPC Account](/docs/clients/wallet#json-rpc-accounts) or [Local Account (Private Key, etc)](/docs/clients/wallet#local-accounts-private-key-mnemonic-etc). If set to `null`, it is assumed that the transport will handle the filling the sender of the transaction. ```ts const { result } = await publicClient.simulateContract({ address: '0xFBA3912Ca04dd458c843e2EE08967fC04f3579c2', abi: wagmiAbi, functionName: 'mint', account: '0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266' // [!code focus] }) ``` ### accessList (optional) * **Type:** [`AccessList`](/docs/glossary/types#accesslist) The access list. ```ts const { result } = await publicClient.simulateContract({ address: '0xFBA3912Ca04dd458c843e2EE08967fC04f3579c2', abi: wagmiAbi, functionName: 'mint', args: [69420], accessList: [{ // [!code focus:4] address: '0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266', storageKeys: ['0x1'], }], account: '0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266' }) ``` ### authorizationList (optional) * **Type:** `AuthorizationList` Signed EIP-7702 Authorization list. ```ts const authorization = await walletClient.signAuthorization({ contractAddress: '0xFBA3912Ca04dd458c843e2EE08967fC04f3579c2', }) const { result } = await publicClient.simulateContract({ address: account.address, abi: wagmiAbi, functionName: 'mint', args: [69420], authorizationList: [authorization], // [!code focus] }) ``` :::note **References** * [EIP-7702 Overview](/docs/eip7702) * [`signAuthorization` Docs](/docs/eip7702/signAuthorization) ::: ### args (optional) * **Type:** Inferred from ABI. Arguments to pass to function call. ```ts const { result } = await publicClient.simulateContract({ address: '0x1dfe7ca09e99d10835bf73044a23b73fc20623df', abi: wagmiAbi, functionName: 'balanceOf', args: ['0xa5cc3c03994DB5b0d9A5eEdD10CabaB0813678AC'], // [!code focus] account: '0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266' }) ``` ### blockNumber (optional) * **Type:** `number` The block number to perform the read against. ```ts const { result } = await publicClient.simulateContract({ address: '0xFBA3912Ca04dd458c843e2EE08967fC04f3579c2', abi: wagmiAbi, functionName: 'mint', account: '0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266' blockNumber: 15121123n, // [!code focus] }) ``` ### blockTag (optional) * **Type:** `'latest' | 'earliest' | 'pending' | 'safe' | 'finalized'` * **Default:** `'latest'` The block tag to perform the read against. ```ts const { result } = await publicClient.simulateContract({ address: '0xFBA3912Ca04dd458c843e2EE08967fC04f3579c2', abi: wagmiAbi, functionName: 'mint', account: '0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266' blockTag: 'safe', // [!code focus] }) ``` ### dataSuffix (optional) * **Type:** `Hex` Data to append to the end of the calldata. Useful for adding a ["domain" tag](https://opensea.notion.site/opensea/Seaport-Order-Attributions-ec2d69bf455041a5baa490941aad307f). ```ts const { result } = await publicClient.simulateContract({ address: '0xFBA3912Ca04dd458c843e2EE08967fC04f3579c2', abi: wagmiAbi, functionName: 'mint', args: [69420], dataSuffix: '0xdeadbeef' // [!code focus] }) ``` ### gas (optional) * **Type:** `bigint` The gas limit for the transaction. ```ts await walletClient.writeContract({ address: '0xFBA3912Ca04dd458c843e2EE08967fC04f3579c2', abi: wagmiAbi, functionName: 'mint', args: [69420], gas: 69420n, // [!code focus] }) ``` ### gasPrice (optional) * **Type:** `bigint` The price (in wei) to pay per gas. Only applies to [Legacy Transactions](/docs/glossary/terms#legacy-transaction). ```ts const { result } = await publicClient.simulateContract({ address: '0xFBA3912Ca04dd458c843e2EE08967fC04f3579c2', abi: wagmiAbi, functionName: 'mint', args: [69420], account: '0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266' gasPrice: parseGwei('20'), // [!code focus] }) ``` ### maxFeePerGas (optional) * **Type:** `bigint` Total fee per gas (in wei), inclusive of `maxPriorityFeePerGas`. Only applies to [EIP-1559 Transactions](/docs/glossary/terms#eip-1559-transaction) ```ts const { result } = await publicClient.simulateContract({ address: '0xFBA3912Ca04dd458c843e2EE08967fC04f3579c2', abi: wagmiAbi, functionName: 'mint', args: [69420], account: '0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266' maxFeePerGas: parseGwei('20'), // [!code focus] }) ``` ### maxPriorityFeePerGas (optional) * **Type:** `bigint` Max priority fee per gas (in wei). Only applies to [EIP-1559 Transactions](/docs/glossary/terms#eip-1559-transaction) ```ts const { result } = await publicClient.simulateContract({ address: '0xFBA3912Ca04dd458c843e2EE08967fC04f3579c2', abi: wagmiAbi, functionName: 'mint', args: [69420], account: '0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266' maxFeePerGas: parseGwei('20'), maxPriorityFeePerGas: parseGwei('2'), // [!code focus] }) ``` ### nonce (optional) * **Type:** `number` Unique number identifying this transaction. ```ts const { result } = await publicClient.simulateContract({ address: '0xFBA3912Ca04dd458c843e2EE08967fC04f3579c2', abi: wagmiAbi, functionName: 'mint', args: [69420], account: '0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266' nonce: 69 // [!code focus] }) ``` ### stateOverride (optional) * **Type:** [`StateOverride`](/docs/glossary/types#stateoverride) The state override set is an optional address-to-state mapping, where each entry specifies some state to be ephemerally overridden prior to executing the call. > Note: By using state overrides, you simulate the contract based on a fake state. Using this is useful for testing purposes, but making a transaction based on the returned `request` object might fail regardless of the simulation result. ```ts const data = await publicClient.simulateContract({ address: '0xFBA3912Ca04dd458c843e2EE08967fC04f3579c2', abi: wagmiAbi, functionName: 'mint', account: '0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266' stateOverride: [ // [!code focus] { // [!code focus] address: '0xa5cc3c03994DB5b0d9A5eEdD10CabaB0813678AC', // [!code focus] balance: parseEther('1'), // [!code focus] stateDiff: [ // [!code focus] { // [!code focus] slot: '0x3ea2f1d0abf3fc66cf29eebb70cbd4e7fe762ef8a09bcc06c8edf641230afec0', // [!code focus] value: '0x00000000000000000000000000000000000000000000000000000000000001a4', // [!code focus] }, // [!code focus] ], // [!code focus] } // [!code focus] ], // [!code focus] }) ``` ### value (optional) * **Type:** `number` Value in wei sent with this transaction. ```ts const { result } = await publicClient.simulateContract({ address: '0xFBA3912Ca04dd458c843e2EE08967fC04f3579c2', abi: wagmiAbi, functionName: 'mint', args: [69420], account: '0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266' value: parseEther('1') // [!code focus] }) ``` ## Live Example Check out the usage of `simulateContract` in the live [Writing to Contracts Example](https://stackblitz.com/github/wevm/viem/tree/main/examples/contracts_writing-to-contracts) below.