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# Add a fallback for RPC requests

It's best practice to ensure your app can still function if your primary RPC endpoint provider fails, enabling JSON-RPC API requests to fall back to an alternative. Wagmi provides a [`fallback`](https://wagmi.sh/core/api/transports/fallback) function that fulfils this need, and is based on the [corresponding Viem function](https://v1.viem.sh/docs/clients/transports/fallback.html).

It enables you to add multiple [Transports](https://viem.sh/docs/clients/intro#transports) — the element of Viem, and therefore Wagmi, which handles requests — to your app's configuration. If the first fails, the request falls back to the next Transport.

## Prerequisites

Install Wagmi and Viem:

```bash
npm install @wagmi/core @wagmi/connectors viem
```

Viem is required for Wagmi to function. The `@wagmi/connectors` package is not strictly necessary, since `fallback` is included in `@wagmi/core`, but you'll most likely need it for your app anyway.

## Usage

You can implement the `fallback` transport by adding it to your app's Wagmi configuration:

```typescript
    export const wagmiConfig = createConfig({
    chains: [linea],
    transports: {
        [linea.id]: fallback([
        http('https://linea-mainnet.infura.io/v3/{YOUR_API_KEY}'), // Primary RPC provider
        http('https://rpc.linea.build'),        // Fallback RPC provider
        ]),
    }
```

In this example, we define a primary RPC endpoint (Infura) and a fallback (`rpc.linea.build`).

See full code example

src/config/wagmiConfig.ts

```typescript
import { createConfig, http, fallback } from '@wagmi/core';
import { jsonRpcProvider } from '@wagmi/core/providers/jsonRpc';
import { linea } from 'viem/chains';

// Add the fallback to the config
export const wagmiConfig = createConfig({
  chains: [linea],
  transports: {
    [linea.id]: fallback([
      http('https://rpc.linea.build'),        // primary RPC HTTP endpoint
      http('https://another.rpc.endpoint/1'), // fallback HTTP endpoint
    ]),
  },
});
```

Optionally, you can also configure the [`rank` parameter](https://v1.viem.sh/docs/clients/transports/fallback.html#rank-optional) to enable your fallback Transport(s) to be used in order of latency and stability.