By default, Microsoft Windows 11 intentionally hides file extensions (the letters at the very end of a filename, like .docx, .pdf, or .exe). Microsoft designed this behavior decades ago because they assumed everyday users would get confused if they accidentally deleted the .txt from a text file, rendering it unreadable. Instead, Windows relies entirely on generic visual icons to tell you what a file is.
This is a catastrophic security vulnerability. If a malicious hacker sends you an email attachment named Invoice-Details.pdf.exe, Windows will hide the .exe part. You will see a file named Invoice-Details.pdf with a fake PDF icon. The moment you double-click it, you will launch a devastating computer virus. You must force Windows 11 to show you the true identity of every single file on your machine.
Method 1: The File Explorer Ribbon (The Fastest Way)
Microsoft completely redesigned the File Explorer interface in Windows 11, making it much easier to reveal file extensions than in previous versions.
- Open the File Explorer (click the yellow folder icon on your taskbar).
- Look at the command ribbon at the very top of the window. Click on the View button.
- A drop-down menu will appear. Move your mouse down to the very bottom and hover over Show.
- A secondary fly-out menu will appear to the right. Click on File name extensions.
A small checkmark will instantly appear next to the setting. Look at the files in your folder; a photograph that was previously named “Vacation” will now correctly display as “Vacation.jpg”. You will instantly know exactly what type of data you are interacting with.
Method 2: Folder Options (The Classic IT Way)
If you prefer the old-school, highly granular control panel that existed in Windows 7 and Windows 10, that exact same interface is still buried deep inside Windows 11.
- Open the File Explorer.
- Click the three horizontal dots (…) on the far right side of the top command ribbon.
- Select Options from the drop-down menu.
- A classic grey “Folder Options” dialog box will appear. Click on the View tab at the top.
- Look in the “Advanced settings” scroll box. It contains a massive list of checkboxes.
- Scroll down until you find the checkbox labeled: Hide extensions for known file types.
- Uncheck that box.
- Click Apply, then click OK.
This does the exact same thing as Method 1, but it guarantees the setting is applied globally across the entire operating system.
How to Change a File Extension
Once you reveal the file extensions, you gain the superpower to manually change a file’s format simply by renaming it.
For example, if you download a raw data file named data.csv (Comma Separated Values) and you want it to open cleanly in Excel, you do not need to convert it using third-party software. Simply right-click the file, click Rename, delete the .csv, and type .txt. When you press Enter, Windows will throw a warning box saying, “If you change a file name extension, the file might become unusable.”
Click Yes. The file’s fundamental identity has now been altered.