Experimental: This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

The SharedStorageWorklet interface of the Shared Storage API represents the shared storage worklet for the current origin.

SharedStorageWorklet does not have its own properties or methods. Rather, it inherits the addModule() method from the Worklet interface. This method is used for adding a module.

Unlike a regular Worklet:

  • If the calling site has not included the Shared Storage API in a privacy sandbox enrollment process, calls to sharedStorageWorklet.addModule() will be rejected.
  • SharedStorageWorklet allows only a single module to be added, for privacy reasons. Even with a successful enrollment, repeated calls to addModule() on the same shared storage worklet will be rejected.

SharedStorageWorklet is accessed via WindowSharedStorage.worklet.

Worklet SharedStorageWorklet


// Randomly assigns a user to a group 0 or 1
function getExperimentGroup() {
  return Math.round(Math.random());

async function injectContent() {
  // Add the module to the shared storage worklet
  await window.sharedStorage.worklet.addModule("ab-testing-worklet.js");

  // Assign user to a random group (0 or 1) and store it in shared storage
  window.sharedStorage.set("ab-testing-group", getExperimentGroup(), {
    ignoreIfPresent: true,

  // Run the URL selection operation
  const fencedFrameConfig = await window.sharedStorage.selectURL(
      { url: `https://your-server.example/content/default-content.html` },
      { url: `https://your-server.example/content/experiment-content-a.html` },
      resolveToConfig: true,

  // Render the chosen URL into a fenced frame
  document.getElementById("content-slot").config = fencedFrameConfig;


See the Shared Storage API landing page for a walkthrough of this example and links to other examples.


Shared Storage API
# sharedstorageworklet

Browser compatibility

BCD tables only load in the browser

See also