Chain Properties

Some chains support additional properties related to blocks and transactions. This is powered by Viem's formatters and serializers. For example, Celo, ZkSync, OP Stack chains all support additional properties. In order to use these properties in a type-safe way, there are a few things you should be aware of.

TIP

Make sure you follow the TypeScript guide's Config Types section before moving on. The easiest way to do this is to use Declaration Merging to "register" your config globally with TypeScript.

import { http, createConfig } from 'wagmi'
import { base, celo, mainnet } from 'wagmi/chains'

export const config = createConfig({
  chains: [base, celo, mainnet],
  transports: {
    [base.id]: http(),
    [celo.id]: http(),
    [mainnet.id]: http(),
  },
})

declare module 'wagmi' {
  interface Register {
    config: typeof config
  }
}

Narrowing Parameters

Once your Config is registered with TypeScript, you are ready to access chain-specifc properties! For example, Celo's feeCurrency is available.

index.tsx

import { parseEther } from 'viem'
import { useSimulateContract } from 'wagmi'

const result = useSimulateContract({
  to: '0xd2135CfB216b74109775236E36d4b433F1DF507B',
  value: parseEther('0.01'),
  feeCurrency: '0x…', 
})

config.ts

import { http, createConfig } from 'wagmi'
import { base, celo, mainnet } from 'wagmi/chains'

export const config = createConfig({
  chains: [base, celo, mainnet],
  transports: {
    [base.id]: http(),
    [celo.id]: http(),
    [mainnet.id]: http(),
  },
})

declare module 'wagmi' {
  interface Register {
    config: typeof config
  }
}

This is great, but if you have multiple chains that support additional properties, your autocomplete could be overwhelmed with all of them. By setting the chainId property to a specifc value (e.g. celo.id), you can narrow parameters to a single chain.

index.tsx

import { parseEther } from 'viem'
import { useSimulateContract } from 'wagmi'
import { celo } from 'wagmi/chains'

const result = useSimulateContract({
  to: '0xd2135CfB216b74109775236E36d4b433F1DF507B',
  value: parseEther('0.01'),
  chainId: celo.id, 
  feeCurrency: '0x…', 
  // ^? (property) feeCurrency?: `0x${string}` | undefined
})

config.ts

import { http, createConfig } from 'wagmi'
import { base, celo, mainnet } from 'wagmi/chains'

export const config = createConfig({
  chains: [base, celo, mainnet],
  transports: {
    [base.id]: http(),
    [celo.id]: http(),
    [mainnet.id]: http(),
  },
})

declare module 'wagmi' {
  interface Register {
    config: typeof config
  }
}

Narrowing Return Types

Return types can also have chain-specific properties attached to them. There are a couple approaches for extracting these properties.

chainId Parameter

Not only can you use the chainId parameter to narrow parameters, you can also use it to narrow the return type.

index.tsx

import { useWaitForTransactionReceipt } from 'wagmi'
import { zkSync } from 'wagmi/chains'

const { data } = useWaitForTransactionReceipt({
  chainId: zkSync.id,
  hash: '0x16854fcdd0219cacf5aec5e4eb2154dac9e406578a1510a6fc48bd0b67e69ea9',
})

data?.logs
//    ^? (property) logs: ZkSyncLog[] | undefined

config.ts

import { http, createConfig } from 'wagmi'
import { base, celo, mainnet } from 'wagmi/chains'

export const config = createConfig({
  chains: [base, celo, mainnet],
  transports: {
    [base.id]: http(),
    [celo.id]: http(),
    [mainnet.id]: http(),
  },
})

declare module 'wagmi' {
  interface Register {
    config: typeof config
  }
}

chainId Data Property

Wagmi internally will set a chainId property on return types that you can use to narrow results. The chainId is determined from the chainId parameter or global state (e.g. connector). You can use this property to help TypeScript narrow the type.

index.tsx

import { useWaitForTransactionReceipt } from 'wagmi'
import { zkSync } from 'wagmi/chains'

const { data } = useWaitForTransactionReceipt({
  hash: '0x16854fcdd0219cacf5aec5e4eb2154dac9e406578a1510a6fc48bd0b67e69ea9',
})

if (data?.chainId === zkSync.id) {
  data?.logs
  //    ^? (property) logs: ZkSyncLog[] | undefined
}

config.ts

import { http, createConfig } from 'wagmi'
import { base, celo, mainnet } from 'wagmi/chains'

export const config = createConfig({
  chains: [base, celo, mainnet],
  transports: {
    [base.id]: http(),
    [celo.id]: http(),
    [mainnet.id]: http(),
  },
})

declare module 'wagmi' {
  interface Register {
    config: typeof config
  }
}

Troubleshooting

If chain properties aren't working, make sure TypeScript is configured correctly. Not all chains have additional properties, to check which ones do, see the Viem repo (chains that have a top-level directory under src/chains support additional properties).