The Problem

Unfortunately, many Windows machines are configured so that they hide the “dot 3” extension after a file name; in other words, the 3 (sometimes 4) letter extension that identfies the type of file does not appear. For instance, a Microsoft Word document might not have .docx on the end of the filename, or a text file might not have .txt after it, or an image might be missing the .jpeg or .gif.

This is easily fixed, and it is important that you fix it, especially if you are going to be making Web pages. Knowing that a file ends with .htm can be extremely helpful, especially if you’ve got an accidental link to the file using .html! In one case, a student had a file that appeared to be named settings.json but wasn’t getting processed as a JSON file; once we turned on extensions, we discovered it was actually named settings.json.txt — no wonder it wasn’t working correctly!

Further, seeing the extension can be a big help in preventing malware. The Anna Kournikova virus used an extension that ended with .shs, a type of file that virtually no one should ever open. Without a visible extension, it would have been impossible to tell just by looking that the attachment was dangerous.

However, Microsoft keeps changing the means by which you can set your computer to reveal the extension, so make sure you use the correct method for your version of Windows.

Windows 95

1. On your desktop, open My Computer.
2. Select the View menu, & then select Options.
3. On the View tab, uncheck the box next to Hide MS-DOS file extensions for file types that are registered.¹
4. Click OK to close Options.
5. Close My Computer.

Windows 98

1. On your desktop, open My Computer.
2. Select the View menu, & then select Folder Options.
3. On the View tab, uncheck the box next to Hide file extensions for known file types.
4. Click OK to close Folder Options.
5. Close My Computer.

Windows ME, Windows 2000, or Windows XP

1. On your desktop, open My Computer. If you don’t see My Computer, then open any folder.
2. Select the Tools menu, & then select Folder Options….
3. In the Folder Options windows, click on the View tab.
4. Uncheck the box next to Hide file extensions for known file types².
5. Click OK to close the Folder Options window.
6. Close the My Computer window.

Windows Vista or 7

1. Click on Start > Control Panel > Appearance and Personalization > Folder Options OR use the Search box on the Start menu & just search for Folder Options there.
2. In the Folder Options windows, click on the View tab.
3. Uncheck the box next to Hide file extensions for known file types.
4. Click OK to close the Folder Options window.

Windows 8 or 8.1

1. From the Start Screen or the Desktop, press Win+W. This should open the Search charm so that it will search for Control Panel applets.
2. Search for Folder Options.
3. In the Folder Options windows, click on the View tab.
4. Uncheck the box next to Hide file extensions for known file types.
5. Click OK to close the Folder Options window.

Windows 10

1. Use Cortana to search for File Explorer Options.
2. In the File Explorer Options window, click on the View tab.
3. Uncheck the box next to Hide file extensions for known file types.
4. Click OK to close the File Explorer Options window.