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

# phone

> Customer's phone number. E.164 format recommended.

Customer's phone number. E.164 format recommended for best matching.

```javascript theme={null}
window._upstack('track', 'lead', {
  email: 'customer@example.com',
  phone: '+15551234567',  // E.164 format: +[country][number]
  value: 0,
  currency: 'USD'
});
```

| Type   | Required | Events                              |
| ------ | -------- | ----------------------------------- |
| string | No       | All events (improves match quality) |

## E.164 Format

The E.164 format is the international standard for phone numbers:

* Start with `+` followed by country code
* No spaces, dashes, or parentheses
* Example: `+15551234567` (US), `+442071234567` (UK)

## Privacy

Phone numbers are normalized and SHA-256 hashed before being sent to destinations.

## Related Properties

<CardGroup cols={2}>
  <Card title="email" icon="envelope" href="/pixel/events/properties/email">
    Customer email — primary identifier.
  </Card>

  <Card title="firstName / lastName" icon="user" href="/pixel/events/properties/name">
    Customer name for identity resolution.
  </Card>
</CardGroup>