How Do I Change the File Extension of a Windows 10 File?

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Trying to change a file extension on a Windows 10 computer isn’t as easy as one might think. Trying to make that little *.txt file in a *.docx file isn’t as simple as just going in and renaming the beast – well, probably not, anyway. There are a few concepts that you’ll need to understand before you just go in and change a file name, as well as a few different scenarios that will require different approaches that we will outline here for you today.

What is a file extension?

A file extension is a group of alphanumerical characters following a period at the end of a filename. The file extension itself indicates what sort of format your file is in. For instance, mypicture.jpg indicates a JPEG file format and mytxtdocument.txt indicates a plain text file format that I can open in Notepad.

File extension vs file format

Your file extension (that’s the .txt part) simply is the text description of the type of file you have, indicating what app the computer is going to select to try and open the file. The file format, the file itself, could be any type of file. The file itself doesn’t know what type of file it is, so doesn’t know what app to use to open it.

Let’s try out an exercise to see how this works.

Type notepad into your Windows search bar and press Enter. This will bring up Notepad. Type into Notepad my text, then click on File, Save As. Browse to a destination folder to save your file. Under the Save as type: selection bar, choose All Files (*.*). Under the File name: bar, type in textdoc.jpg and then click Save. Type in file explorer into your Windows search bar and press Enter. Browse to the folder you saved textdoc.jpg in. Double click on the file to open it.

The computer will automatically open your default picture viewing app (for me it’s Windows Photos) and it will give you a message like “It appears we don’t support this file format.”

However, if we right click on the file in File Explorer, select Open With…, then Choose Another App, scroll down and select More Apps, then select Notepad – we will open our file in Notepad again and see it operating just fine.

This indicates a mismatched file extension and file format. We can still open our file if we select the right app for the actual file format, but our computer thinks it is a JPEG file (from the file extension) and so opens it with an app that displays pictures. Because it is a text file, the picture viewer doesn’t know what to do with it and so it isn’t displayed.

Changing a mismatched file extension and file format

If you have a situation similar to the above example, where your file has been saved with the wrong file extension (but you know the real format of the file), then this is an easy fix. Let’s demonstrate with the above example.

Right click on your textdoc.jpg in File Explorer, then select Rename. Delete the jpg at the end of the filename and replace it with txt instead. You will get a warning message that says “If you change a file name extension, the file might become unstable. Are you sure you want to change it?”. Click on the Yes button. Now double click on your file labels textdoc.txt. It will now open your file easily again with Notepad.

This can be used with any files when the file extension has been mislabelled – but only in this specific case.

Changing a file to a similar format

Let’s say you have a Microsoft Word file (.docx) and you want to change it to a plain text file (.txt). How can you do this?

First of all, you’ll need to open the file in Microsoft Word (or similar – programs such as Open Office can open .docx files). Once in Microsoft Word you can select Save As, then in the Save As Type: selection bar you have the open to save as Plain Text (*.txt). You can create a new copy of the file in plain text format and then open in Notepad.

Many programs have this Save As function where you can save a copy of your file as a similar format. However, some do not. Let’s take a look at this case next.

Changing a file extension where Save As the type you want is not available

Let’s say that you’ve saved a picture file off the internet, and it’s saved it as a Portable Network Graphics file – so the extension is .png. You double click to open it and it opens with Windows Photos. You find Save As, but there’s only the option to save it as .png. What do you do? Why won’t it let you save it as a .jpg? They’re both picture files, right?

They may both be picture files, but they’re both stored and arranged a little differently by your computer. This means that you need to convert the file to .jpg format. Changing the file extension isn’t going to do anything, except make you unable to open the file (like we saw in our first example).

Instead, we need to open our browser and type into our search bar convert png to jpg. You’ll see a list of online tools available that will do the job for you, so select one and away you go. You’ll receive back from the tool a new file in .jpg format, with the right extension.

That’s it!

So those are the three different cases under which you will be able to change file extensions under Windows 10. For help in cleaning up your computer, including junk files, and making it run smoother and faster, why not try out SafePCKit with our free download, or learn how to disable extensions on your Chrome browser in our blog post.

Julia is an ex software developer turned content writer who has a penchant for tech talk and loves linguistics. Australian born, she now subscribes to the location-independent movement, wandering in search of sunshine, techno, and the perfect espresso martini.

Julia SJ

Julia is an ex software developer turned content writer who has a penchant for tech talk and loves linguistics. Australian born, she now subscribes to the location-independent movement, wandering in search of sunshine, techno, and the perfect espresso martini.