TaskSignal: priority property

Limited availability

This feature is not Baseline because it does not work in some of the most widely-used browsers.

Note: This feature is available in Web Workers.

The read-only priority property of the TaskSignal interface indicates the signal priority.

The initial value is set in the associated TaskController by specifying it as an argument to the TaskController constructor (by default it is "user-visible"). The priority of the signal can be changed by calling TaskController.setPriority() on the associated controller.

For tasks with a mutable priority, this value is used to set the initial task priority and later to change it. Tasks with an immutable priority will ignore the value.

Value

A string indicating the signal priority. This will be one of: "user-blocking", "user-visible", "background".

Examples

The priority is most commonly used by developers to determine the new priority following prioritychange events. See TaskSignal: prioritychange event for a live example.

Specifications

Specification
Prioritized Task Scheduling
# dom-tasksignal-priority

Browser compatibility

desktop mobile
Chrome
Edge
Firefox
Opera
Safari
Chrome Android
Firefox for Android
Opera Android
Safari on iOS
Samsung Internet
WebView Android
WebView on iOS
priority
Chrome – Full support
Chrome 94 (Release date: 2021-09-21)
footnote Full support
Edge – Full support
Edge 94 (Release date: 2021-09-24)
footnote Full support
Firefox – Full support
Firefox 142 (Release date: 2025-08-19)
footnote Full support
Opera – Full support
Opera 80 (Release date: 2021-10-05)
footnote Full support
Safari – No support
Safari
footnote No support
Chrome Android – Full support
Chrome Android 94 (Release date: 2021-09-21)
footnote Full support
Firefox for Android – Full support
Firefox for Android 142 (Release date: 2025-08-19)
footnote Full support
Opera Android – Full support
Opera Android 66 (Release date: 2021-12-15)
footnote Full support
Safari on iOS – No support
Safari on iOS
footnote No support
Samsung Internet – Full support
Samsung Internet 17 (Release date: 2022-05-04)
footnote Full support
WebView Android – Full support
WebView Android 94 (Release date: 2021-09-21)
footnote Full support
WebView on iOS – No support
WebView on iOS
footnote No support

Legend

Tip: you can click/tap on a cell for more information.

Full support
Full support
No support
No support