The mode read-only property of the Request interface contains the mode of the request (e.g., cors, no-cors, same-origin, or navigate.) This is used to determine if cross-origin requests lead to valid responses, and which properties of the response are readable.


var myMode = request.mode;


A RequestMode value.

The associated mode, available values of which are:

  • same-origin — If a request is made to another origin with this mode set, the result is simply an error. You could use this to ensure that a request is always being made to your origin.
  • no-cors — Prevents the method from being anything other than HEAD, GET or POST, and the headers from being anything other than simple headers. If any ServiceWorkers intercept these requests, they may not add or override any headers except for those that are simple headers. In addition, JavaScript may not access any properties of the resulting Response. This ensures that ServiceWorkers do not affect the semantics of the Web and prevents security and privacy issues arising from leaking data across domains.
  • cors — Allows cross-origin requests, for example to access various APIs offered by 3rd party vendors. These are expected to adhere to the CORS protocol. Only a limited set of headers are exposed in the Response, but the body is readable.
  • navigate — A mode for supporting navigation. The navigate value is intended to be used only by HTML navigation. A navigate request is created only while navigating between documents.

If not defined, the default value of cors is assumed.


In the following snippet, we create a new request using the Request.Request() constructor (for an image file in the same directory as the script), then save the request mode in a variable:

var myRequest = new Request('flowers.jpg');
var myMode = myRequest.mode; // returns "cors" by default


Specification Status Comment
The definition of 'mode' in that specification.
Living Standard Initial definition

Browser compatibility


FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support42 Yes39 No29 No
navigate mode49 Yes46 No ? No
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidOpera AndroidiOS SafariSamsung Internet
Basic support4949 Yes No No No5.0
navigate mode No49 Yes No No No5.0


See also

Document Tags and Contributors

Last updated by: fscholz,