Service-Worker-Navigation-Preload header

Limited availability

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

See full compatibility

The HTTP Service-Worker-Navigation-Preload request header indicates that the request was the result of a fetch() operation made during service worker navigation preloading. It allows a server to respond with a different resource than for a normal fetch().

If a different response may result from setting this header, the server must include a Vary: Service-Worker-Navigation-Preload header in responses to ensure that different responses are cached.

For more information see NavigationPreloadManager.setHeaderValue() (and NavigationPreloadManager).

Header type	Request header
Forbidden request header	No

Syntax

http

Service-Worker-Navigation-Preload: <value>

Directives

<value>: An arbitrary value that indicates what data should be sent in the response to the preload request. This defaults to true. It maybe set to any other string value in the service worker, using NavigationPreloadManager.setHeaderValue().

Examples

Service worker navigation preloading headers

The following request header is sent by default in navigation preload requests:

http

Service-Worker-Navigation-Preload: true

The service worker can set a different header value using NavigationPreloadManager.setHeaderValue(). For example, in order to request that a fragment of the requested resource be returned in JSON format, the value could be set with the string json_fragment1.

http

Service-Worker-Navigation-Preload: json_fragment1

Specifications

Specification
Service Workers Nightly # handle-fetch

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
`Service-Worker-Navigation-Preload` request header	Chrome – Full support Chrome 59 (Release date: 2017-06-05) footnote Full support	Edge – Full support Edge 18 (Release date: 2018-10-02) footnote Full support	Firefox – No support Firefox 97 (Release date: 2022-02-08) disabled disabled From version 97 users must explicitly set the `dom.serviceWorkers.navigationPreload.enabled` preference to `true`. To change preferences in Firefox, visit about:config. Firefox – Preview support Firefox Nightly footnote Preview browser support	Opera – Full support Opera 46 (Release date: 2017-06-22) footnote Full support	Safari – Full support Safari 15.4 (Release date: 2022-03-14) footnote Full support	Chrome Android – Full support Chrome Android 59 (Release date: 2017-06-06) footnote Full support	Firefox for Android – No support Firefox for Android footnote No support	Opera Android – Full support Opera Android 43 (Release date: 2017-09-27) footnote Full support	Safari on iOS – Full support Safari on iOS 15.4 (Release date: 2022-03-14) footnote Full support	Samsung Internet – Full support Samsung Internet 7 (Release date: 2018-03-16) footnote Full support	WebView Android – Full support WebView Android 59 (Release date: 2017-06-06) footnote Full support	WebView on iOS – Full support WebView on iOS 15.4 (Release date: 2022-03-14) footnote Full support

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

Full support: Full support
In development. Supported in a pre-release version.: In development. Supported in a pre-release version.
No support: No support
: User must explicitly enable this feature.
: Has more compatibility info.

Service-Worker-Navigation-Preload header

Syntax

Directives

Examples

Service worker navigation preloading headers

Specifications

Browser compatibility

Legend

See also