A file with the .reg file extension is a Windows Registry file. It's a text-based file created by exporting values from the Registry and can also be used to add or change values in the Registry.

What is the Windows Registry?

The Windows Registry is a hierarchical database where 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 (folders) on the left and values on the right. Navigating it is much like browsing for files using File Explorer. Select a key on the left and you'll see the values that key contains on the right.

The Registry features a complex set of keys and values numbering in the thousands, so clicking through it looking for things isn't 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. We've even published a bunch of them ourselves over the years.

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're created by exporting selected keys from the Registry. And while you can use them to back up the registry (particularly important before making changes!), most of the time you'll see them made available 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 a bit, and then share the file with others. They can then just double-click the file to make those same changes in their own Registry. We do this here at How-To Geek when we share a Registry hack. We'll show you where to dig around in the Registry to make changes yourself and also share a Registry Hack that automatically manages specific registry entries for you.

We've also got a great article on making your own Registry hacks if you're interested.

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 alter and delete important information, blindly opening one could render your system unstable or even inoperable. That being said, you may want to consider backing up the Registry (and your computer!) beforehand.

If you want to apply a REG file to your own Registry, all you have to do is double-click the file. You'll be asked to give permission for Windows to changed the Registry based on what's in the file.

If you want to see what a REG file contains (or even modify one yourself), all you need is a text editor like Notepad or Notepad++.

Right-click any REG 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.

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