Skip to content

Migration Guide

If you are coming from an earlier version of viem, you will need to make sure to update the following APIs listed below.

2.x.x Breaking changes

The 2.x.x release includes very minor breaking changes to the Contract Instances API, entrypoints, chain modules, and miscellaneous actions + utilities listed below.

Not ready to migrate? Head to the 1.x.x docs.

Actions: Modified getContract Client API

The publicClient and walletClient parameters of the getContract API has been removed in favour of client to support Client's that extend (ie. a Wallet Client extended with Public Actions).

Read more.

import { getContract } from 'viem'
import { publicClient, walletClient } from './client'
 
const contract = getContract({
  abi,
  address,
  publicClient, 
  walletClient, 
  client: { 
    public: publicClient, 
    wallet: walletClient, 
  } 
})

Removed entrypoints

The following entrypoints have been removed:

  • viem/abi
  • viem/contract
  • viem/public
  • viem/test
  • viem/wallet

You can import the entrypoints directly from viem:

import { encodeAbiParameters } from 'viem/abi'
import { getContract } from 'viem/contract'
import { getBlock } from 'viem/public'
import { mine } from 'viem/test'
import { sendTransaction } from 'viem/wallet'
import { 
  encodeAbiParameters, 
  getContract, 
  getBlock, 
  mine, 
  sendTransaction, 
} from 'viem'

Moved chain-specific exports in viem/chains/utils

Chain-specific exports in viem/chains/utils have been moved to viem/{celo|op-stack|zksync}:

import {
  parseTransactionCelo,
  parseTransaction 
  serializeTransactionCelo, 
  serializeTransaction 
  // ...
} from 'viem/chains/utils'
} from 'viem/celo'
 
import {
  // ...
} from 'viem/chains/utils'
} from 'viem/op-stack'
 
import {
  parseTransactionZkSync, 
  parseTransaction, 
  serializeTransactionZkSync, 
  serializeTransaction, 
  // ...
} from 'viem/chains/utils'
} from 'viem/zksync'

Actions: getBlockNumber

The maxAge parameter has been removed in favor of cacheTime.

const blockNumber = await client.getBlockNumber({
  maxAge: 84_600
  cacheTime: 84_600
})

Actions: OnLogFn & OnLogParameter types

The OnLogFn & OnLogParameter types have been renamed.

import {
  OnLogFn, 
  WatchEventOnLogsFn, 
  OnLogParameter, 
  WatchEventOnLogsParameter, 
} from 'viem'

Actions: prepareRequest

The prepareRequest Action has been renamed to prepareTransactionRequest and moved to viem/actions entrypoint.

import {
  prepareRequest, 
  prepareTransactionRequest, 
} from 'viem'
} from 'viem/actions'

Actions: SimulateContractParameters & SimulateContractReturnType types

Note the following breaking generic slot changes:

type SimulateContractParameters<
  TAbi,
  TFunctionName,
  TArgs, // Args added to Slot 2
  TChain,
  TChainOverride,
  TAccountOverride,
>
 
type SimulateContractReturnType<
  TAbi,
  TFunctionName,
  TArgs, // Args added to Slot 2
  TChain,
  TAccount, // Account added to Slot 4
  TChainOverride,
  TAccountOverride,
>

Utilities: Removed extractFunctionParts, extractFunctionName, extractFunctionParams, extractFunctionType

The extractFunctionParts, extractFunctionName, extractFunctionParams, extractFunctionType utility functions have been removed. You can use the parseAbiItem utility function from abitype instead.

Utilities: Renamed bytesToBigint

The bytesToBigint utility function has been renamed to bytesToBigInt.

import {
  bytesToBigint, 
  bytesToBigInt, 
} from 'viem'

Utilities: Renamed chain types

The following chain types have been renamed:

import {
  Formatter, 
  ChainFormatter, 
  Formatters, 
  ChainFormatters, 
  Serializers, 
  ChainSerializers, 
  ExtractFormatterExclude, 
  ExtractChainFormatterExclude, 
  ExtractFormatterParameters, 
  ExtractChainFormatterParameters, 
  ExtractFormatterReturnType, 
  ExtractChainFormatterReturnType, 
} from 'viem'

1.x.x Breaking changes

The 1.x.x release only includes very minor changes to the behavior in event log decoding, and removes the redundant ethers.js Wallet Adapter. If you do not directly use these APIs, you do not need to update any of your code for this version.

Removed ethersWalletToAccount

The ethersWalletToAccount adapter has been removed.

This adapter was introduced when viem did not have Private Key & HD Accounts. Since 0.2, viem provides all the utilities needed to create and import Private Key & HD Accounts.

If you still need it, you can copy + paste the old implementation.

logIndex & transactionIndex on Logs

logIndex & transactionIndex on Log now return a number instead of a bigint.

const log: Log = {
  ...
  logIndex: 1n, 
  logIndex: 1, 
  transactionIndex: 1n, 
  transactionIndex: 1, 
  ...
}

Minor: decodeEventLog behavior change

decodeEventLog no longer attempts to partially decode events. If the Log does not conform to the ABI (mismatch between the number of indexed/non-indexed arguments to topics/data), it will throw an error.

For example, the following Log will throw an error as there is a mismatch in non-indexed arguments & data length.

decodeEventLog({
  abi: parseAbi(['event Transfer(address indexed, address, uint256)']),
  // `data` should be 64 bytes, but is only 32 bytes.
  data: '0x0000000000000000000000000000000000000000000000000000000000000001'
  topics: [
    '0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef',
    '0x000000000000000000000000f39fd6e51aad88f6f4ce6ab8827279cfffb92266',
  ]
})

Previously, the above would only decode the indexed arguments.

If you would like to partially decode event logs (previous behavior), you can turn off strict mode:

decodeEventLog({
  abi: parseAbi(['event Transfer(address indexed, address, uint256)']),
  data: '0x0000000000000000000000000000000000000000000000000000000000000001'
  topics: [
    '0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef',
    '0x000000000000000000000000f39fd6e51aad88f6f4ce6ab8827279cfffb92266',
  ],
  strict: false
})

0.3.x Breaking changes

The 0.3.x release only includes breaking changes around RPC errors. If you do not directly use the APIs listed below, you do not need to update any of your code for this version.

Renamed RequestError to RpcError

RequestError was renamed RpcError for clarity.

import { RequestError } from 'viem'
import { RpcError } from 'viem'
 
throw new RequestError(new Error('An error occurred.'))  
throw new RpcError(new Error('An error occurred.'))

Removed RpcRequestError

RpcRequestError was removed. Use RpcError instead.

import { RpcRequestError } from 'viem'
import { RpcError } from 'viem'
 
throw new RpcRequestError(new Error('An error occurred.')) 
throw new RpcError(new Error('An error occurred.'))

Renamed RpcError to RpcRequestError

RpcError was renamed RpcRequestError for consistency.

import { RpcError } from 'viem'
import { RpcRequestError } from 'viem'
 
const err = new RpcError({ 
const err = new RpcRequestError({  
  body: { foo: 'bar' },
  error: { code: 420, message: 'Error' },
  url: 'https://example-rpc.com',
})

0.2.x Breaking changes

chain is required for sendTransaction, writeContract, deployContract

A chain is now required for the sendTransaction, writeContract, deployContract Actions.

You can hoist the Chain on the Client:

import { createWalletClient, custom, getAccount } from 'viem'
import { mainnet } from 'viem/chains'
 
export const walletClient = createWalletClient({
  chain: mainnet, 
  transport: custom(window.ethereum)
})
 
const account = getAccount('0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266')
 
const hash = await walletClient.sendTransaction({ 
  account,
  to: '0x70997970c51812dc3a010c7d01b50e0d17dc79c8',
  value: 1000000000000000000n
})

Alternatively, you can pass the Chain directly to the Action:

import { createWalletClient, custom, getAccount } from 'viem'
import { mainnet } from 'viem/chains'
 
export const walletClient = createWalletClient({
  chain: mainnet, 
  transport: custom(window.ethereum)
})
 
const account = getAccount('0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266')
 
const hash = await walletClient.sendTransaction({ 
  account,
  chain: mainnet, 
  to: '0x70997970c51812dc3a010c7d01b50e0d17dc79c8',
  value: 1000000000000000000n
})

recoverAddress, recoverMessageAddress, verifyMessage are now async

he following functions are now async functions instead of synchronous functions:

  • recoverAddress
  • recoverMessageAddress
  • verifyMessage
import { recoverMessageAddress } from 'viem'
 
recoverMessageAddress({ message: 'hello world', signature: '0x...' }) 
await recoverMessageAddress({ message: 'hello world', signature: '0x...' })

assertChain removed from sendTransaction

Removed assertChain argument on sendTransaction, writeContract & deployContract. If you wish to bypass the chain check (not recommended unless for testing purposes), you can pass chain: null.

await walletClient.sendTransaction({
  assertChain: false, 
  chain: null, 
  ...
})

getAccount removed

Removed the getAccount function.

For JSON-RPC Accounts, use the address itself.

You can now pass the address directly to the account option.

import { createWalletClient, custom } from 'viem'
import { mainnet } from 'viem/chains'
 
const address = '0xFBA3912Ca04dd458c843e2EE08967fC04f3579c2'
 
const client = createWalletClient({
  account: getAccount(address), 
  account: address, 
  chain: mainnet,
  transport: custom(window.ethereum)
})

For Ethers Wallet Adapter, use ethersWalletToAccount.

If you were using the Ethers Wallet adapter, you can use the ethersWalletToAccount function.

Note: viem 0.2.0 now has a Private Key & Mnemonic Account implementation. You probably do not need this adapter anymore. This adapter may be removed in a future version.

import { createWalletClient, custom } from 'viem'
import { mainnet } from 'viem/chains'
import { getAccount } from 'viem/ethers'
import { ethersWalletToAccount } from 'viem/ethers'
import { Wallet } from 'ethers'
 
const account = getAccount(new Wallet('0x...')) 
const account = ethersWalletToAccount(new Wallet('0x...')) 
 
const client = createWalletClient({
  account,
  chain: mainnet,
  transport: custom(window.ethereum)
})

For Local Accounts, use toAccount.

If you are using a custom signing implementation, you can use the toAccount function.

import { createWalletClient, http, getAccount } from 'viem'
import { createWalletClient, http } from 'viem'
import { toAccount } from 'viem/accounts'
import { mainnet } from 'viem/chains'
import { getAddress, signMessage, signTransaction } from './sign-utils' 
 
const privateKey = '0x...' 
const account = getAccount({ 
const account = toAccount({ 
  address: getAddress(privateKey),
  signMessage(message) {
    return signMessage(message, privateKey)
  },
  signTransaction(transaction) {
    return signTransaction(transaction, privateKey)
  },
  signTypedData(typedData) {
    return signTypedData(typedData, privateKey)
  }
})
 
const client = createWalletClient({
  account,
  chain: mainnet,
  transport: http()
})

data renamed in signMessage

Renamed the data parameter in signMessage to message.

walletClient.signMessage({
  data: 'hello world', 
  message: 'hello world', 
})