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

# validatePhoneNumber

```ts theme={null}
function validatePhoneNumber(phoneNumber: string): void;
```

Validates a phone number is in E.164 format.

E.164 format requirements:

* Starts with +
* Followed by country code (1-3 digits)
* Followed by subscriber number
* Total length: 1-15 digits (excluding the + prefix)

## Parameters

| Parameter     | Type     | Description                   |
| ------------- | -------- | ----------------------------- |
| `phoneNumber` | `string` | The phone number to validate. |

## Returns

`void`

## Throws

Error if the phone number is not in valid E.164 format.

## Example

```typescript theme={null}
// Valid formats
validatePhoneNumber("+14155552671");  // US
validatePhoneNumber("+442071838750"); // UK
validatePhoneNumber("+81312345678");  // Japan

// Invalid formats (will throw)
validatePhoneNumber("4155552671");     // Missing +
validatePhoneNumber("+1-415-555-2671"); // Contains hyphens
validatePhoneNumber("+0412345678");    // Starts with 0
```