SSN is an obsolete file format associated with Shutdown Scheduler application. Files with SSN extension were typically found on Microsoft Windows XP and2000 systems, which are no longer developed and supported by Microsoft.

SSN files stored data in plain text format. They contained information used by scheduled computer shutdown routine. Shutdown Scheduler application could be used to create an execute automated compute shutdown schedule. Shutdown Scheduler project was dropped with the release of Windows Vista operating system.