---
title: PerformanceTiming.unloadEventStart
slug: Web/API/PerformanceTiming/unloadEventStart
tags:
  - API
  - Backwards compatibility
  - Deprecated
  - Navigation Timing
  - PerformanceTiming
  - Property
  - Read-only
  - legacy
browser-compat: api.PerformanceTiming.unloadEventStart
---
{{APIRef("Navigation Timing")}}{{Deprecated_Header}}

> **Warning:** This interface of this property is deprecated in the [Navigation Timing Level 2 specification](https://w3c.github.io/navigation-timing/#obsolete). Please use the {{domxref("PerformanceNavigationTiming")}}
> interface instead.

The legacy
**`PerformanceTiming.unloadEventStart`**
read-only property returns an `unsigned long long` representing the moment,
in milliseconds since the UNIX epoch, the {{event("unload")}} event has been thrown. If
there is no previous document, or if the previous document, or one of the needed
redirects, is not of the same origin, the value returned is `0`.

## Syntax

```js
time = performanceTiming.unloadEventStart;
```

## Specifications

This feature is no longer on track to become a standard, as the [Navigation Timing specification](https://w3c.github.io/navigation-timing/#obsolete) has marked it as deprecated.
Use the {{domxref("PerformanceNavigationTiming")}} interface instead.

## Browser compatibility

{{Compat}}

## See also

- The {{domxref("PerformanceTiming")}} interface it belongs to.
