WorkletSharedStorage: get() method

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

The get() method of the WorkletSharedStorage interface retrieves a value from shared storage.





A string representing the key of the key-value pair you want to retrieve.

Return value

A Promise that fulfills with either a string equal to the value of the retrieved key-value pair or undefined if the specified key is not found in the shared storage.



Thrown if:


Measuring K+ frequency

The following example measures the K+ frequency of content views. Sometimes described as "effective frequency", K frequency refers to the minimum number of views before a user will recognize or recall certain content (often used in the context of ad views).

The main page script:

// k-frequency-measurement.js

async function injectContent() {
  // Load the Shared Storage worklet
  await window.sharedStorage.worklet.addModule('k-freq-measurement-worklet.js');

  // Run the K-frequency measurement operation
  await'k-freq-measurement', { data: { kFreq: 3, contentId: 123 });


The worklet module is shown below:

// k-frequency-measurement-worklet.js

// Scale factor for handling noise added to data
const SCALE_FACTOR = 65536;

 * The bucket key must be a number, and in this case, it is simply the content
 * ID itself. For more complex bucket key construction, see other use cases in
 * this demo.
function convertContentIdToBucket(contentId) {
  return BigInt(contentId);

class KFreqMeasurementOperation {
  async run(data) {
    const { kFreq, contentId } = data;

    // Read from Shared Storage
    const hasReportedContentKey = "has-reported-content";
    const impressionCountKey = "impression-count";
    const hasReportedContent =
      (await this.sharedStorage.get(hasReportedContentKey)) === "true";
    const impressionCount = parseInt(
      (await this.sharedStorage.get(impressionCountKey)) || 0,

    // Do not report if a report has been sent already
    if (hasReportedContent) {

    // Check impression count against frequency limit
    if (impressionCount < kFreq) {
      await this.sharedStorage.set(impressionCountKey, impressionCount + 1);

    // Generate the aggregation key and the aggregatable value
    const bucket = convertContentIdToBucket(contentId);
    const value = 1 * SCALE_FACTOR;

    // Send an aggregatable report via the Private Aggregation API
    privateAggregation.sendHistogramReport({ bucket, value });

    // Set the report submission status flag
    await this.sharedStorage.set(hasReportedContentKey, "true");

// Register the operation
register("k-freq-measurement", KFreqMeasurementOperation);

For more details about this example, see K+ frequency measurement. See the Shared Storage API landing page for links to other examples.


Shared Storage API
# dom-workletsharedstorage-get

Browser compatibility

BCD tables only load in the browser

See also