Every file on your Windows PC, whether it’s a system or application file, has an extension. File extensions are the letters added after the period in a file name.

For example, a Microsoft Word file has the DOCX extension. So, a Word file should look like this:

New_document.docx

Here's how Word files look

The extension tells the operating system the software application required to run the file. When you double-click a Word file, for example, Windows automatically opens it in Word. You’ll also notice that files have different icons depending on their extensions.

But what if you have a file without an extension? In that case, Windows won’t launch the file since it can’t associate it with any program. Instead, a pop-up will appear showing suggested apps.

The file isn't associated with any app

The file will also come with a generic, blank file icon.

An example of a file without any exception

Why Do Some Applications Have Files with No Extensions?

By default, Windows does not display file extensions. You’ll have to turn the setting on in File Explorer to see them. So, if you’re not seeing extensions, the setting is likely turned off.

That said, some program files don’t come with file extensions. These are files you’ll find in an application’s installation folder. In most cases, especially if these files are in all caps and are not executable, they’re plaintext.

How to Open Files Without Extensions in Windows 11 and Windows 10

As we mentioned, file extensions are usually hidden in Windows 10 and 11. That’s because tampering with extensions could damage a file and render it permanently unreadable.

If you want to see a file’s extension, right-click it and select Properties. Under the General tab of the Properties dialog, you’ll see the file’s extension beside “Type of file.”

That said, if you downloaded a file and it came with the generic file icon, then it has no extension.

If you know the type of file you downloaded or copied to your system, you can manually change its extension to allow Windows to associate it with the right program. To do that, you have to make extensions visible.

Follow these steps if you use a Windows 10 computer:

  1. Tap the File Explorer icon in the taskbar. If you don’t have the icon, you can tap Win + E on your keyboard or right-click the Start button and select File Explorer.
  2. Once the window shows up, go to the top and click on the View tab.
  3. Next, tick the checkbox next to File Name Extensions. That’s it.
  4. You can also go through the Folder Options dialog to change the setting. Here’s how:
  • After you open File Explorer, click on the View tab and select Options.
  • Once the Folder Options dialog opens, switch to the View tab.
  • Next, go to the Advanced Settings list and uncheck the box beside “Hide extensions for known file types.”
  • Click on the OK button.

Follow these steps if you use a Windows 11 machine:

  1. Tap the File Explorer icon in the taskbar. If you don’t have the icon, you can tap Win + E on your keyboard or right-click the Start button and select File Explorer.
  2. Once you see the Quick Access view of the File Explorer window, go to the top of the interface and click on View.
  3. Once the View menu appears, select Show > File Name Extensions. File extensions will now be visible.

How to see extensions on Windows 11

  1. Alternatively, you can go through the Folder Options dialog. Follow these steps:
  • Click on the three dots beside the View button and select Options.
  • Once the Folder Options dialog opens, switch to the View tab.
  • Next, go to the Advanced Settings list and uncheck the box beside “Hide extensions for known file types.”
  • Click on the OK button.

Methods to unhide file extensions on Windows

Now that extensions are visible, you can change your file extensions as you wish. Remember that using the wrong extension renders the file unreadable. For example, if you change a file’s extension from DOCX (Word file) to AVI (video file), Windows will return an error whenever you try to open it.

If the file you’re working with doesn’t have an extension but you know what application should run it, enter a period (.) after its last letter followed by the correct extension.

How to Open a File With No Extension

Now, if you don’t know the type of file you’re dealing with, that’s a different story. That means you don’t know what extension to enter. In this case, you’ll have to use third-party freeware that is designed to identify the extensions of unknown files. Here are some tools that can help you:

  • File Identifier from Toolsley
  • TrID File Identifier
  • Download DROID (Digital Record Object IDentification)

We’ll show you how to use these tools.

Toolsley File Identifier

Toolsley File Identifier comes in web extension and online versions. With the online version, you have to open www.toolsley.com and upload your file. You can either click on the Select File button to browse for and open the file or drag and drop it into the box. The tool will automatically identify the file and display its details.

Toolsley File Identifier

It’s natural to be wary about uploading your files to a random website. However, this shouldn’t bother you. That’s because you’re not uploading the file to any third-party server. The detection work is handled by your computer using the site’s JavaScript tool. This means there are no file size limits and you don’t have to worry about internet upload speeds and malicious activity.

The Toolsley File Identifier web extension is similar to the online tool. However, in this case, you’ll have to open the Chrome extension whenever you want to identify an unknown file.

TrID

TrID is one of the most powerful and well-known file identifiers around. The program is still in active development and has an ever-growing database of definitions used to identify file types. That means new file types will be added to its database after they are released.

The tool comes in three different versions. They are as follows:

TrID – a command-line tool

TrIDNet – a GUI version

TrID Online – the tool’s web version

How to Use TrID

Using the command-line program involves running a simple argument to check for an unknown file’s extension. You’ll first have to download the tool alongside its definition files from its website. Make sure every file you download is saved to the same folder. Now, to identify a file, load up the Command Prompt and run the following argument:

trid.exe unknown.file

You can make things easier by using a batch file. Once you create the batch file, all you have to do is drag and drop the file you want to identify onto the batch file’s icon.

Follow these steps to create the batch file:

  1. Open Notepad.
  2. Copy and paste the following into the blank note:

@echo off

CD /d “%~dp0”

trid.exe -w %1

Use the trid.exe unknown.file argument

  1. Save the note as TrID.bat.

It would be a good idea to save the file to your desktop. This way, it would be easy to drag and drop files onto the icon.

How to Use TrIDNet

The GUI version is simpler to use. Head to the tool’s webpage to download the package and extract it. After that, download the XML definitions and extract them to the same folder as the previous package. Note that you’ll have to install .NET 3.5 to get the program to work.

Now, open the folder where you extracted the files and launch TrIDNet. After the interface appears, browse for the unknown file or drag and drop it into the window. The tool will now display likely file types. A percentage is shown beside each file type suggestion, indicating the program’s level of certainty.

How to Use TrID Online

Open this link and use the Browse button to select the unknown file whose extension you want to identify. Note that the website doesn’t have the drag and drop functionality, so you must use the Browse option.

DROID (Digital Record Object IDentification)

This tool stands out from the rest because it allows you to identify multiple unknown files at once. Many people have confidence in this program since it was developed by the UK National Archives.

To use it, head to the National Archives website and download the compressed package under Current Version.

Use DROID to identify multiple unknown files at once

Extract it and open the DROID.bat file. Click on the Add button to browse for unknown files or drag and drop the files into the window.

Conclusion

Dealing with an unknown file type can be frustrating, especially if you need the file for urgent work. Unfortunately, Windows has no way to suggest the type of file you’re dealing with. Even if you open the Microsoft Store, you’ll be none the wiser. We are confident the solutions above will help you identify the file and append the correct extension to open it.

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Ensure you always have a powerful antivirus program installed as downloaded files without extension names could be malware applications. Some malicious programs are also responsible for removing file extensions and causing other forms of havoc.