# Timing-Allow-Origin header

The HTTP **`Timing-Allow-Origin`** [response header](https://developer.mozilla.org/en-US/docs/Glossary/response%20header) specifies origins that are allowed to see values of attributes retrieved via features of the [Resource Timing API](https://developer.mozilla.org/en-US/docs/Web/API/Performance_API/Resource_timing) that are otherwise restricted for cross-origin resources.
Without it, the browser reports these values as zero, an empty string, or an empty array.
For the list of affected properties, see [Cross-origin restrictions](https://developer.mozilla.org/en-US/docs/Web/API/PerformanceResourceTiming#cross-origin_restrictions) in the [PerformanceResourceTiming](https://developer.mozilla.org/en-US/docs/Web/API/PerformanceResourceTiming) reference.

The browser checks this header on cross-origin responses: same-origin resources expose full timing information without it.

This header is independent of [CORS](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/CORS).
Passing the CORS check doesn't grant access to detailed timing information.
Conversely, `Timing-Allow-Origin` doesn't expose properties that describe the response itself, such as its body size, content type, or status code.

<table class="properties">
  <tbody>
    <tr>
      <th scope="row">Header type</th>
      <td>[Response header](https://developer.mozilla.org/en-US/docs/Glossary/Response%20header)</td>
    </tr>
  </tbody>
</table>

## Syntax

```http
Timing-Allow-Origin: *
Timing-Allow-Origin: <origin>, …, <originN>
```

## Directives

- `*` (wildcard)
  - : Any origin may see timing resources.
- `<origin>`
  - : Specifies a URI that may see the timing resources. You can specify multiple origins, separated by commas.

## Examples

### Using Timing-Allow-Origin

To allow any resource to see timing resources:

```http
Timing-Allow-Origin: *
```

To allow `https://developer.mozilla.org` to see timing resources, you can specify:

```http
Timing-Allow-Origin: https://developer.mozilla.org
```

## Specifications

## Browser compatibility

## See also

- [PerformanceResourceTiming](https://developer.mozilla.org/en-US/docs/Web/API/PerformanceResourceTiming)
- [Resource Timing API](https://developer.mozilla.org/en-US/docs/Web/API/Performance_API/Resource_timing)
- [Server-Timing](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Server-Timing) header
- [Vary](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Vary) header