Event ID is a uniquely identifiable number for a specific logged event on a Windows PC. And, like any other event, the Audit success or Audit failure for each successful or failed event in Event Viewer is logged with a unique number, known as event ID. For example, if an account logon attempt fails on Windows 11/10, you may see An account failed to log on error message with Event ID 4625 for that particular failed event in the Event Viewer window.