> ## Documentation Index
> Fetch the complete documentation index at: https://docs.neynar.com/llms.txt
> Use this file to discover all available pages before exploring further.

# App Client

If you're building a [connected app](https://docs.farcaster.xyz/learn/what-is-farcaster/apps#connected-apps) and want users to sign in with Farcaster, use an `AppClient`.

You can use an `AppClient` to create a Farcaster Auth relay channel, generate a deep link to request a signature from the user's Farcaster wallet app, and verify the returned signature.

```ts theme={"system"}
import { createAppClient, viemConnector } from '@farcaster/auth-client';

const appClient = createAppClient({
  relay: 'https://relay.farcaster.xyz',
  ethereum: viemConnector(),
});
```

## Parameters

| Parameter  | Type                | Description                                                                                                                                                                                                                                                     | Required |
| ---------- | ------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | -------- |
| `ethereum` | `EthereumConnector` | <p>An Ethereum connector, used to query the Farcaster contracts and verify smart contract wallet signatures. `@farcaster/auth-client` currently provides only the `viem` connector type.</p> <p>To use a custom RPC, pass an RPC URL to the viem connector.</p> | Yes      |
| `relay`    | `string`            | Relay server URL. Defaults to the public relay at `https://relay.farcaster.xyz`                                                                                                                                                                                 | No       |
| `version`  | `string`            | Farcaster Auth version. Defaults to `"v1"`                                                                                                                                                                                                                      | No       |