How to count Azure DevOps Server (on premise) license usage from exported audit log?

To check and count Azure DevOps Server license usage, under your on prem Azure DevOps Server, go to Organization settings -> Audit log and click on Export audit log (as shown in your image) and download the CSV file. Open it in excel and look for the Last Accessed (UTC) column in the CSV file.

As per my understanding, this column shows when a user last accessed Azure DevOps. Put a filter and remove duplicates and count these users (they consume a license). Count only AD user accounts that have a date in this column and ignore system accounts and internal groups. This count gives you the number of active users consuming a license.

For example-

1. If an AD user account has a date listed in the Last Accessed (UTC) column, that means they’ve logged in and are actively using the system. These users do consume a license.
2. If an AD user account has no entry in the Last Accessed (UTC) column, that means they haven’t logged in at all. These users do not take up a license.
3. Even if someone is in the local Administrators group on the server, they won’t count toward license usage unless they actually log in. If they haven’t accessed the system, they don’t use a license.
4. Accounts like Build Service and Agent Pool Service are system-level accounts, not real users. They don’t count toward license consumption.
5. Groups like Build Administrators or other internal DevOps roles don’t consume a license on their own. However, the actual users inside those groups might, but only if they have accessed the system.

In short, only real user accounts that have logged into Azure DevOps take up a license. If someone has never accessed it, or if it’s a system account or group, it doesn’t count.