The replacesClientId read-only property of the FetchEvent interface is the id of the client that is being replaced during a page navigation.

For example, when navigating from page A to page B replacesClientId is the ID of the client associated with page A. It can be an empty string when navigating from about:blank to another page, as about:blank's client will be reused, rather than be replaced.

Additionally, if the fetch isn't a navigation, replacesClientId will be an empty string. This could be used to access/communicate with a client that will imminently be replaced, right before a navigation.


var myReplacedClientId = fetchEvent.replacesClientId;


A DOMString.


self.addEventListener('fetch', function(event) {


Specification Status Comment
Service Workers
The definition of 'replacesClientId' in that specification.
Working Draft Initial definition.

Browser compatibility

ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
replacesClientIdChrome No support NoEdge No support 18 — 79Firefox Full support 65IE No support NoOpera No support NoSafari No support NoWebView Android No support NoChrome Android No support NoFirefox Android Full support 65Opera Android No support NoSafari iOS No support NoSamsung Internet Android No support No


Full support
Full support
No support
No support

See also