Document: requestStorageAccessFor() method

Syntax
Parameters
Return value
Exceptions
Description
Examples
Specifications
Browser compatibility
See also

The requestStorageAccessFor() method of the {{domxref("Document")}} interface allows top-level sites to request third-party cookie access on behalf of embedded content originating from another site in the same related website set. It returns a {{jsxref("Promise")}} that resolves if the access was granted, and rejects if access was denied.

Syntax

requestStorageAccessFor(requestedOrigin)

Parameters

requestedOrigin
- : A string representing the URL of the origin you are requesting third-party cookie access for.

Return value

A {{jsxref("Promise")}} that fulfills with undefined if the access to third-party cookies was granted and rejects if access was denied.

requestStorageAccessFor() requests are automatically denied unless the top-level content is currently processing a user gesture such as a tap or click ({{Glossary("transient activation")}}), or unless permission was already granted previously. If permission was not previously granted, they must run inside a user gesture-based event handler. The user gesture behavior depends on the state of the promise:

If the promise resolves (i.e., permission was granted), then the user gesture has not been consumed, so the script can subsequently call APIs requiring a user gesture.
If the promise is rejected (i.e., permission was not granted), then the user gesture has been consumed, so the script can't do anything that requires a gesture. This prevents scripts from calling requestStorageAccessFor() again if permission is denied.

Exceptions

InvalidStateError {{domxref("DOMException")}}
- : Thrown if the current {{domxref("Document")}} is not yet active.
NotAllowedError {{domxref("DOMException")}}
- : Thrown if:
  - The document's window is not a secure context.
  - The document is not the top-level document.
  - The document has a null origin.
  - The supplied requestedOrigin is opaque.
  - The top-level and embedded sites are not in the same related website set.
  - The embedding {{htmlelement("iframe")}} is sandboxed, and the allow-storage-access-by-user-activation token is not set.
  - Usage is blocked by a {{httpheader("Permissions-Policy/storage-access", "storage-access")}} Permissions Policy.
  - Usage is denied by the user agent's permission request to use the API.
{{jsxref("TypeError")}}
- : Thrown if requestedOrigin is not a valid URL.

Description

The requestStorageAccessFor() method addresses challenges in adopting the Storage Access API on top-level sites that use cross-site images or scripts requiring cookies. It is relevant to user agents that by default block access to third-party, unpartitioned cookies to improve privacy (e.g., to prevent tracking), and is a proposed extension of the Storage Access API.

requestStorageAccessFor() can enable third-party cookie access for cross-site resources directly embedded into a top-level site that are unable to request storage access themselves, for example {{htmlelement("img")}} elements. Cross-site content embedded in <iframe>s that has its own logic and resources and needs third-party cookie access should request storage access via {{domxref("Document.requestStorageAccess()")}}.

To check whether permission to access third-party cookies has already been granted via requestStorageAccessFor(), you can call {{domxref("Permissions.query()")}}, specifying the feature name "top-level-storage-access". This is different from the feature name used for the regular {{domxref("Document.requestStorageAccess()")}} method, which is "storage-access".

The Permissions.query() call must specify the embedded origin; for example:

navigator.permissions.query({
  name: "top-level-storage-access",
  requestedOrigin: "https://www.example.com",
});

[!NOTE] Usage of this feature may be blocked by a {{httpheader("Permissions-Policy/storage-access", "storage-access")}} Permissions Policy set on your server (the same one that controls the rest of the Storage Access API). In addition, the document must pass additional browser-specific checks such as allowlists, blocklists, on-device classification, user settings, or anti-clickjacking heuristics.

Examples

function rSAFor() {
  if ("requestStorageAccessFor" in document) {
    document.requestStorageAccessFor("https://example.com").then(
      (res) => {
        // Use storage access
        doThingsWithCookies();
      },
      (err) => {
        // Handle errors
      },
    );
  }
}

After a successful requestStorageAccessFor() call, cross-site requests will include cookies if they include CORS / crossorigin, so sites may want to wait before triggering a request. Such requests must use the credentials: "include" option and resources must include the crossorigin="use-credentials" attribute.

For example:

function checkCookie() {
  fetch("https://example.com/getcookies.json", {
    method: "GET",
    credentials: "include",
  })
    .then((response) => response.json())
    .then((json) => {
      // Do something
    });
}

[!NOTE] See Using the Storage Access API for a more complete example.