What is an EX_ File?

A file with the EX_ file extension is a Compressed EXE file.

This format stores an EXE file in a smaller size to save storage space on installation discs. You might also find the EX_ format within compressed installation files that you download from the internet.

Windows is always ready to execute an EXE file, but not an EX_ file, providing a limited amount of security. For example, you can't accidentally open an EX_ file to run the (possibly malicious or unwanted) program until the file extension is renamed to .EXE.

An EX_ file isn't a usable file in and of itself. You'll first need to convert the EX_ file to an EXE file so you can execute or use the file. You can do this using the expand command, available from the Command Prompt in Windows.

Warning: Take great care when opening executable file formats like EXE that you receive over email or download from websites you're not familiar with. Files of this type can be extremely dangerous to not only the system files but also any personal files you have. See my List of Executable File Extensions for a listing of other file extensions to avoid and why.

EX_ files are often made using the Makecab program available in Windows, which is accessible via command-line through the makecab command. However, to open an EX_ file, open Command Prompt and then execute the expand command as I do in this example (but change file.ex_ to the name of your own EX_ file):

expand file.ex_ file.exe

The new EXE file will be created as named. No changes will be made to the original EX_ file.

Note: If the command isn't working, it's probably because Command Prompt doesn't know what folder the EX_ file is in. There are a few ways to fix this...

In Windows, open the folder that has the EX_ file and then Shift+Right Click in an open area of the folder. In the context menu, select the option that says to open Command Prompt in that location, and then enter the command again.

You can also quickly fill in the location of the EX_ file by just dragging the actual file onto the Command Prompt window. However, be sure to type expand first, and then drag the file onto the Command Prompt window.

If the EX_ file is simply renamed from .EXE to .EX_, and isn't compressed at all, then you can just rename the extension to .EXE to use it like you would any other file. You can then just double-click it to open it in Windows.

Tip: Use Notepad++ to open the EX_ file if the above methods don't work. Some EX_ files may not be EXE files at all but are used by a different program entirely. If so, Notepad++ may reveal some descriptive information that can help you determine what program should be used to open it.

If you find that an application on your PC does try to open the EX_ file but it's the wrong application or if you would rather have another installed program open EX_ files, see my How To Change the Default Program for a Specific File Extension guide for making that change in Windows.

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Let me know what kinds of problems you're having with opening or using the EX_ file and I'll see what I can do to help. If the EX_ file was part of an installation package, especially one that I can also download and look at, that'd be really helpful information.