How to Hide / Show Known File Extensions

A file's file name extension shows the file type that determines the default application to open it. Known file types are set to be hidden by default in Windows 7.

Folder Options

1. Open Windows Explorer (or any folder) then select Organize then Choose Folder and Search Options
   
   


2. In the Folder Options window, select View then scroll to the option that says "Hide extensions for known file types"
   
   


3. By default it should be checked. Un-check it to show the known file extensions

Registry Edit

Warning: Editing the registry may cause your system to become unstable. Always back up your registry before making any changes

1. Click Start then type regedit on the search field then press Enter.


2. In the Registry Editor window, make a backup by clicking File then Export. Save the registry back up to a convenient location (C:\ for example.)
   
   


3. Navigate to this folder: HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced and find the HideFileExt key.
   
   


4. Right-click on the HideFileExt key then select Modify


5. In the Edit DWORD window, the default setting should be 1 (hide known file extension). To show the file extensions, replace 1 with number 0 then click OK.
   
   


6. Close regedit and refresh the folder to see the changes.