Windows 10 Change File Extension

A file name extension is a set of characters in the end of file name that determine which program should open it. Windows 10 hides usually it, but you can choose to make them visible. Usually, file name extensions should not be changed because you might not be able to open or edit the file after doing so.

Sometimes, however, changing the file name extension can be useful—such as when you need to change a text file (.txt) to an HTML file (.htm) so that you can view it in a web browser. When dealing with documents, pictures, music or even software install files, it’s very helpful to know file extension.

Show File Extensions and Hidden Files

By default, Windows 10 hides most file extensions so, when you’re browsing through your files, you can’t easily see what type of file they are. Your quarterly report, for example, will appear as "3dqreport" instead of "3dqreport.pptx" while that web page you saved will display as "homepage" rather than "homepage.htm" or "homepage.html".

Microsoft has been disabling extensions by default for the past several versions of its OS in a misguided effort to simplify the file system for users. In an effort to protect you from yourself, Microsoft also hides certain operating system files from you by default. But what if you need to find these files or edit them to troubleshoot? And can’t you trust yourself not to delete important files?

Here’s how to show extensions and hidden files in Windows 10.

  1. Navigate to the control panel. You can get there by hitting Windows + X and selecting Control Panel, or just go to the ‘Start Menu’ and click on “Control Panel”.

    Windows 10 Control Panel
  2. Open File Explorer Options. If you don’t see the icon for it, change the control panel view (in the upper right corner) to large or small icons.

    Windows 10 File Explorer Options
  3. Navigate to the View tab.

    File Explorer Options View tab
  4. Toggle "Hidden files and folders" to "Show hidden files, folders and drives".

    Windows 10 Show File Extension
  5. Uncheck "Hide empty drives," "Hide extensions for known file types" and "Hide protected operating system files."

    Windows 10 Show Protected Extension
  6. Click Yes when warned about unhiding protected files.

    Confirm to show Hidden & Protected files
  7. Click Ok. Your File extension is now visible.

Change File Extensions in Windows 10

To change a file name extension:

  1. Make sure that file name extensions are visible. To learn how to do this, see Show or hide file name extensions.
  2. Right-click the file you want to change, and then click Rename.
  3. Delete the file name extension, type the new extension, and then press Enter.
  4. Windows will warn you that changing the file name extension might cause the file to stop working properly. If you are certain that the extension you typed will work with the program you’re using, click Yes to confirm the change.

Change Default Programs in Windows 10

Windows 10 gives you several ways to change the default program associations. Here are the fastest and most effective ways to point your files towards the programs you want to use them with.

Default Programs (Control Panel)

This method is for PC users who prefer the old-school Control Panel, and it doesn’t require opening the new finger-friendly Settings menu inherited from Windows 8. Open the Windows 10 Control Panel, then click “Programs,” then “Default Programs.” The first two entries on this list are what you’re interested in.

Windows 10 Default Programs

If you’d like to set a single program as the default for all the types of files it’s capable of opening, click “set your default programs.” This screen opens a list of your installed programs in the column on the left. Click a program in the left column, then click “set this program as default” to apply all of the file type associations that the program includes.

Windows 10 Change Default Programs

For more fine-grain control, click “Choose defaults for this program.” You’ll be presented with a detailed list of all the file type associations for the program, which you can enable or disable by clicking the check box on the left of each entry.

If all you need to do is associate a single file type with a specific program, click the “Back” button in the navigation bar until you’re at the Default Programs screen, then click “Associate a file type or protocol with specific program.” In this screen you’re given a list of all the registered file types currently on your PC’s storage drive. To change the default program for a single file, find it in the list and click it. (You can click the Name, Description, and Current Default column to sort in alphabetical or reverse alphabetical order.)

Click “Change program” to open the Associations screen, where you can choose from the first half-dozen or so programs that can open the file. If the program you want to use doesn’t appear on the list, click “more apps” to see all the programs that can handle that file type. If the program still doesn’t show up, click “look for another app on this PC” to select it manually using File Explorer.

Changing a default app in File Explorer

If you’re in a hurry and just want to set the default program for a single file type, you can do this from anywhere in File Explorer, or even on the desktop. Right-click on a single file, then place the cursor on “Open with.” From this nested menu you can select from the most commonly-used relevant programs on your PC.

Changing a Default App in Windows 10

To change the default program permanently, click “Choose another app” at the bottom of the sub-menu. This will open a small association menu for that file type. Click “Always use this app to open [file type] files,” then select the program you want from the list or find it via the “Look for another app on this PC” command. You’ve now permanently reset the file type association. You can change it again in the Control Panel or Settings screens above.