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User ID - Web Tracking (analytics.js)

This guide describes how to implement User ID using analytics.js.

  1. Overview
  2. Implementation
  3. Example


User ID enables the analysis of groups of sessions, across devices, using a unique, persistent, and non-personally identifiable ID string representing a user. To learn why you should implement the User ID, see Benefits of using the User ID feature.


To implement the User ID on the web:

  1. Provide your own unique, persistent, and non-personally identifiable string ID to represent each signed-in user. This ID is most often provided by an authentication system.
  2. Set the User ID on the tracker:
    ga('create', 'UA-XXXX-Y', { 'userId': 'USER_ID' });
    ga('send', 'pageview');


A typical authentication system should be able to provide a unique, non-personally identifiable and persistent ID, for a signed in user. This ID can be sent to Google Analytics when a user signs into your website.

For a website that implements such an authentication system and uses PHP, the standard analytics.js code snippet could be dynamically updated to set the userId when a suitable ID for the user is available, as in this example:

<!-- Google Analytics -->
(i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();a=s.createElement(o),

// New Google Analytics code to set User ID.
// $userId is a unique, persistent, and non-personally identifiable string ID.
if (isset($userId)) {
  $gacode = "ga('create', 'UA-XXXX-Y', { 'userId': '%s' });";
  echo sprintf($gacode, $userId);
} else {
  $gacode = "ga('create', 'UA-XXXX-Y');";
  echo sprintf($gacode);

ga('send', 'pageview');

<!-- End Google Analytics -->


  • $userId is a variable set by the server only if the user has successfully authenticated to your service.