Secure context: This feature is available only in secure contexts (HTTPS), in some or all supporting browsers.

getClientExtensionResults() is a method of the PublicKeyCredential interface that returns an ArrayBuffer which contains a map between the extensions identifiers and their results after having being processed by the client.

During the creation or fetching of a PublicKeyCredential (respectively via navigator.credentials.create() and navigator.credentials.get()), it is possible to have "custom" processing by the client for different extensions which are respectively given by PublicKeyCredentialCreationOptions.extensions and PublicKeyCredentialRequestOptions.extensions.

Note: Extensions are optional and different browsers may recognize different extensions. All extensions are optional for the client to process them: if a browser does not know of a given extension, that will not cause any failure.

Note: This method may only be used in top-level contexts and will not be available in an <iframe> for example.





Return value

An ArrayBuffer containing the result of the processing of the different extensions by the client. This object contains a map between the extensions' identifiers and their results from the processing.

Warning: As of March 2019, only appId (used during creation with PublicKeyCredentialRequestOptions.extensions) is supported by Chromium and Firefox does not seem to support any extension.


const publicKey = {
  // Here are the extensions (as "inputs")
  extensions: {
    loc: true, // This extension has been defined to include location information in attestation
    uvi: true, // user verification index: how the user was verified
  challenge: new Uint8Array(16) /* from the server */,
  rp: {
    name: "Example CORP",
    id: "",
  user: {
    id: new Uint8Array(16) /* from the server */,
    name: "",
    displayName: "Carina Anand",
  pubKeyCredParams: [
      type: "public-key",
      alg: -7,

  .create({ publicKey })
  .then((newCredentialInfo) => {
    const myBuffer = newCredentialInfo.getClientExtensionResults();
    // myBuffer will contain the result of any of the processing of the "loc" and "uvi" extensions
  .catch((err) => {


Web Authentication: An API for accessing Public Key Credentials - Level 3
# ref-for-dom-publickeycredential-getclientextensionresults

Browser compatibility

BCD tables only load in the browser

See also