| title | Request: mode property |
|---|---|
| short-title | mode |
| slug | Web/API/Request/mode |
| page-type | web-api-instance-property |
| browser-compat | api.Request.mode |
{{APIRef("Fetch API")}}{{AvailableInWorkers}}
The mode read-only property of the {{domxref("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.
To construct a request with a specific mode, pass the desired value as the {{domxref("RequestInit", "", "mode")}} option to the {{domxref("Request.Request()")}} constructor.
Note that setting particular modes, especially no-cors, places restrictions on the request methods and headers that may be used, and prevents JavaScript from accessing the response headers or body. See the documentation for {{domxref("RequestInit", "", "mode")}} for more details.
One of the following values:
-
same-origin- : Disallows cross-origin requests. If a request is made to another origin with this mode set, the result is an error.
-
no-cors- : Disables CORS for cross-origin requests. The response is opaque, meaning that its headers and body are not available to JavaScript.
-
cors- : If the request is cross-origin then it will use the Cross-Origin Resource Sharing (CORS) mechanism.
-
navigate- : A mode for supporting navigation. The
navigatevalue is intended to be used only by HTML navigation. A navigate request is created only while navigating between documents.
- : A mode for supporting navigation. The
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
{{domxref("Request.Request", "Request()")}} constructor, the value of the mode property
for that Request is set to cors.
However, for requests created other than by the {{domxref("Request.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 {{HTMLElement("link")}} or {{HTMLElement("script")}} elements
(except when used with modules), or {{HTMLElement("img")}}, {{HTMLElement("audio")}},
{{HTMLElement("video")}}, {{HTMLElement("object")}}, {{HTMLElement("embed")}}, or
{{HTMLElement("iframe")}} elements.
In the following snippet, we create a new request using the {{domxref("Request.Request", "Request()")}} constructor (for an image file in the same directory as the script), then save the request mode in a variable:
const myRequest = new Request("flowers.jpg");
const myMode = myRequest.mode; // returns "cors" by default{{Specifications}}
{{Compat}}
