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# Custom (EIP-1193)

## Overview

The [`custom`](/docs/transports/custom) transport wraps an
[EIP-1193](https://eips.ethereum.org/EIPS/eip-1193)-compatible provider as a
[Transport](/docs/transports). The provider must have a `request` method.

Use it with injected wallets, provider libraries, or your own provider.
[`Provider.from`](/docs/utilities/provider/from) from `viem/utils` normalizes provider errors.

```ts twoslash
import { custom } from 'viem'

const transport = custom({
  async request({ method, params }) {
    // ...
    return null
  },
})
```

## Recipes

### Wrapping an Existing Provider

Any object with an EIP-1193 `request` method works, such as an injected wallet provider or one from a provider library.

```ts twoslash
import { custom } from 'viem'
import 'viem/window'

const transport = custom(window.ethereum!) // [!code focus]
```

### Restricting RPC Methods

Limit a custom provider to specific RPC methods when it should only handle part of your request flow.

```ts twoslash
import { custom } from 'viem'
import 'viem/window'

const transport = custom(window.ethereum!, {
  methods: { include: ['eth_call'] }, // [!code focus]
})
```

### Configuring Retries

Tune retry behavior when the wrapped provider needs a different retry budget or backoff delay.

```ts twoslash
import { custom } from 'viem'
import 'viem/window'

const transport = custom(window.ethereum!, {
  retryCount: 5, // [!code focus]
  retryDelay: 200, // [!code focus]
})
```

## `custom`

Creates a transport from an EIP-1193-compatible provider.

### Usage

```ts twoslash
import { custom } from 'viem'

const transport = custom({
  async request({ method, params }) {
    // ...
    return null
  },
})
```

### Parameters

#### provider

* **Type:** `{ request(...args): Promise<any> }`

An EIP-1193-compatible provider.

```ts twoslash
import { custom } from 'viem'
import 'viem/window'
// ---cut---
const transport = custom(window.ethereum!) // [!code focus]
```

#### options.key

* **Type:** `string`
* **Default:** `'custom'`

Transport key.

```ts twoslash
import { custom } from 'viem'
import 'viem/window'
// ---cut---
const transport = custom(window.ethereum!, {
  key: 'custom', // [!code focus]
})
```

#### options.methods

* **Type:** `{ include?: string[] } | { exclude?: string[] }`

RPC methods to include or exclude.

```ts twoslash
import { custom } from 'viem'
import 'viem/window'
// ---cut---
const transport = custom(window.ethereum!, {
  methods: { include: ['eth_call'] }, // [!code focus]
})
```

#### options.name

* **Type:** `string`
* **Default:** `'Custom Provider'`

Transport name.

```ts twoslash
import { custom } from 'viem'
import 'viem/window'
// ---cut---
const transport = custom(window.ethereum!, {
  name: 'Custom Provider', // [!code focus]
})
```

#### options.retryCount

* **Type:** `number`
* **Default:** `3`

Max retries per request.

```ts twoslash
import { custom } from 'viem'
import 'viem/window'
// ---cut---
const transport = custom(window.ethereum!, {
  retryCount: 5, // [!code focus]
})
```

#### options.retryDelay

* **Type:** `number`
* **Default:** `150`

Base delay (ms) between retries.

```ts twoslash
import { custom } from 'viem'
import 'viem/window'
// ---cut---
const transport = custom(window.ethereum!, {
  retryDelay: 200, // [!code focus]
})
```

### Return Value

`Transport<'custom'>`

A custom transport that delegates each request to the provider.