How to identify your users in Google Analytics while complying with terms of service

Identify users in Google Analytics

In Google Analytics we’re not allowed to track personally identifiable information (PII) such as usernames that would be identifiable by a 3rd party including Google.  But you can instead send an identifier which is known only to you. You can identify your users in your backend and that is your responsibility, not Google's. This kind of identification should not publicly available to 3rd parties without authentication, authorization etc.

There are some definite gotchas when implementing this type of solution. Most notably, you need to deal with data sampling applied via the API. From the Google Analytics API docs:

Google Analytics calculates certain combinations of dimensions and metrics on the fly. To return the data in a reasonable time, Google Analytics only processes a sample of the data. In these situations, the metric data returned in each entry includes a confidence interval.

References:

1. Identifying your users in Google Analytics while complying with section 7 of the terms of service
2. Google Analytics Forum | Best way to track individual users
3. Merging Google Analytics with your Data Warehouse