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

This feature is no longer recommended. Though some browsers might still support it, it may have already been removed from the relevant web standards, may be in the process of being dropped, or may only be kept for compatibility purposes. Avoid using it, and update existing code if possible; see the compatibility table at the bottom of this page to guide your decision. Be aware that this feature may cease to work at any time.

The additionalData property of the PasswordCredential interface takes one of a FormData instance, a URLSearchParams instance, or null. The data in the objects will be added to the request body and sent to the remote endpoint with the credentials.


passwordCredential.additionalData = formData
formData = passwordCredential.additionalData
passwordCredential.additionalData = urlSearchParams
ulrSearchParams = passwordCredential.additionalData


One of a FormData instance, a URLSearchParams instance, or null.


The following example creates a FormData object with an appended CSRF token. It then stores the form object in the additionalData parameter, before sending it to server in a call to fetch.

//The options object was previously created. 
navigator.credentials.get(options).then(function(creds) {
  if (creds.type == 'password') {
    var form = new FormData();
    var csrf_token = document.querySelector('csrf_token').value;
    form.append('csrf_token', csrf_token);

    creds.additionalData = form;

    fetch('', {
      method: 'POST',
      credentials: creds


Specification Status Comment
Credential Management Level 1 Working Draft Initial definition.

Browser compatibility

Update compatibility data on GitHub
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
Chrome Full support 51Edge ? Firefox ? IE ? Opera ? Safari ? WebView Android Full support 51Chrome Android Full support 51Firefox Android ? Opera Android ? Safari iOS ? Samsung Internet Android ?


Full support  
Full support
Compatibility unknown  
Compatibility unknown
Experimental. Expect behavior to change in the future.
Experimental. Expect behavior to change in the future.
Deprecated. Not for use in new websites.
Deprecated. Not for use in new websites.