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# Add Chain \[chains.add]

Adds an EVM chain to the wallet.

## Usage

This example adds an EVM chain to the wallet.

:::code-group
```ts twoslash [example.ts]
import { optimism } from 'viem/chains'
import { client } from './viem.config'

await client.chains.add({ chain: optimism })
```

```ts twoslash [viem.config.ts] filename="viem.config.ts"
import { Client, custom, walletActions } from 'viem'
import 'viem/window'

export const client = Client.create({
  transport: custom(window.ethereum!),
}).extend(walletActions())
```
:::

### Standalone Action

Call `Actions.chains.add` directly by passing the Client as the first argument.

:::code-group
```ts twoslash [example.ts]
import { Actions } from 'viem'
import { optimism } from 'viem/chains'
import { client } from './viem.config'

await Actions.chains.add(client, { chain: optimism })
```

```ts twoslash [viem.config.ts] filename="viem.config.ts"
import { Client, custom } from 'viem'
import 'viem/window'

export const client = Client.create({
  transport: custom(window.ethereum!),
})
```
:::

## Return Value

`void`

No value is returned.

## Parameters

### chain

* **Type:** `Chain`

The chain to add to the wallet.

```ts twoslash
import { Actions } from 'viem'
import { optimism } from 'viem/chains'
// [!include ~/snippets/docs/reference-client.ts:setup]
// ---cut---
await Actions.chains.add(client, {
  chain: optimism, // [!code focus]
})
```