A file with the .reg file extension is a Windows Registry file.
What is the Windows Registry?
The Windows Registry is a hierarchical database of Windows and many applications store configuration settings. You can access the registry via the Registry Editor app into Windows. The view is divided into a list of keys on the left and values on the right. It is much like browsing for files using File Explorer.
The Registry features a set of keys and values numbering in the thousands, so clicking through is not particularly useful unless you just like exploring. You're much more likely to use the registry editor because you've found a tweak or hack on a website that you'd like to try out.
RELATED: Windows Registry Demystified: What You Can Do With It
What is a REG File?
A REG file is just a text file with the .reg extension. They are created by exporting selected keys from the registry. You can use them to back up the registry (most importantly before making changes!), Most of the time you can see them as downloadable files on the same sites that show you how to perform a registry hack.  You can make manual changes to the registry, export those changes, clean up the file, and then share the file with others. They can then just double-click the file to make those same changes in their own registry. How do we geek when we share a registry hack.
We've been hacking your own registry hacks if you
RELATED: How to Make Your Own Windows Registry Hacks
How Do I Open a REG File?
There is a severe risk when opening REG files if you don ' t know where they came from. Because these files can not be broken, they can not be broken.
If you want to apply a REG file to your own registry, you have to double-click the file.
If you want to see what a REG file contains, you can Notepad or Notepad ++.
Right-click any .REF file and then click the "Edit" command to open the file in your default text editor.
If you want to use a text editor other than your default, right-click the file and then click the "Open With" command.
The file will open in the text editor where you will be able to read, edit , or delete any lines from the file before merging it to your registry.