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.
Syntax
var myMode = request.mode;
Value
-
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 thanHEAD
,GET
orPOST
, 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 resultingResponse
. 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 theResponse
, but the body is readable.navigate
— A mode for supporting navigation. Thenavigate
value is intended to be used only by HTML navigation. A navigate request is created only while navigating between documents.
Default mode
Requests can be initiated in a variety of ways, and the mode for a request depends on the particular means by which it was initiated.
For example, when a Request
object is created using the Request.Request
constructor, the value of the mode
property for that Request
is set to cors
.
However, for requests created other than by the Request.Request
constructor, no-cors
is typically used as the mode; for example, for embedded resources where the request is initiated from markup, unless the crossorigin
attribute is present, the request is in most cases made using the no-cors
mode — that is, for the <link>
or <script>
elements (except when used with modules), or <img>
, <audio>
, <video>
, <object>
, <embed>
, or <iframe>
elements.
Example
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
Specifications
Specification | Status | Comment |
---|---|---|
Fetch The definition of 'mode' in that specification. |
Living Standard | Initial definition |
Browser compatibility
Desktop | Mobile | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
mode | Chrome Full support 42 | Edge Full support 14 | Firefox Full support 39 | IE No support No | Opera Full support 29 | Safari No support No | WebView Android Full support 49 | Chrome Android Full support 49 | Firefox Android No support No | Opera Android No support No | Safari iOS No support No | Samsung Internet Android Full support 5.0 |
navigate mode | Chrome Full support 49 | Edge Full support ≤18 | Firefox Full support 46 | IE No support No | Opera ? | Safari No support No | WebView Android No support No | Chrome Android Full support 49 | Firefox Android No support No | Opera Android No support No | Safari iOS No support No | Samsung Internet Android Full support 5.0 |
Legend
- Full support
- Full support
- No support
- No support
- Compatibility unknown
- Compatibility unknown
- Experimental. Expect behavior to change in the future.
- Experimental. Expect behavior to change in the future.