This is an experimental technology
Because this technology's specification has not stabilized, check the compatibility table for usage in various browsers. Also note that the syntax and behavior of an experimental technology is subject to change in future versions of browsers as the specification changes.

The mode read-only property of the Request interface contains the mode of the request (e.g., cors, no-cors, cors-with-forced-preflight, 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:

  • 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. If any ServiceWorkers intercept these requests, they may not add or override any headers except for these. 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.


var <var>myMode</var> = <var>request</var>.mode;


A RequestMode value.


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

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support 42.0 39 (39) No support


No support
navigate mode 49.0 46 (46) No support ? No support
Feature Android Android Webview Firefox Mobile (Gecko) Firefox OS (Gecko) IE Phone Opera Mobile Safari Mobile Chrome for Android
Basic support No support 49.0 No support No support No support No support No support 49.0
navigate mode No support No support No support No support No support No support No support 49.0

See also


© 2016 Mozilla Contributors
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.

API Experimental Fetch mode Property Reference request