System Administrators have access to the System Setup | Whitelist where they can add, edit, or delete the 'allowed' file extensions for files. The extensions that are on this list allow the user to open, upload, check in, and convert in the system. Depending on your agency's security requirements System Administrators may also check the field 'Allow Files Without Extensions'. This will allows users to add, view, and check in files that do not contain a file extension.