What Is a REG File?
A file with the .reg file extension is a registration file used by the Windows Registry. These files can contain hives, keys, and values. They can be created from scratch in a text editor or can be produced by the Windows Registry when backing up parts of it.
What REG Files Are Used For
There are two major ways to edit the Windows registry:
Open Registry Editor and then make registry changes manually. Use a REG file.
Think of a REG file as a set of instructions for changing the Windows Registry. Everything in it explains the changes that should be made to the current state of the registry. In other words, and in general, any differences between the REG file being executed and the Windows Registry will result in an addition or removal of whatever keys and values are involved.
Example REG File
For example, here are the contents of a simple REG file that adds value to a specific key in the registry. In this case, the goal is to add the data necessary for the classic fake Blue Screen of Death: That CrashOnCtrlScroll value isn’t included in the registry by default. You could open Registry Editor and create it yourself, manually, or you could build those instructions in a REG file and have it added automatically. Another way to look at these files is to think of them as tools to edit the registry. You can save lots of time when making the same registry changes on multiple computers. Just create one REG file with the changes you want to make, and then apply them instantly on multiple PCs.
How to View, Change, and Build REG Files
These are text-based files. Looking back at the example above, you can clearly see the numbers, path, and letters that make it up. This means you can open one and read everything in it, as well as edit it, using nothing more than a text editor. Windows Notepad is the text editor included in Windows. You can use that program with a REG file by right-clicking or tapping-and-holding the file and choosing Edit. If you like, you can use Windows Notepad every time you need to read or edit the file, but there are other free text editor tools that are easier to work with if you plan on working with these files a lot. Since REG files are nothing more than text files, any text editor can also be used to build a brand new one from scratch. Using our example from above yet again, all you have to do to create the file is open the text editor and then type those instructions exactly as they’re written. Next, choose All Files (.) as the Save as type, and save it as something memorable, with the .REG extension, of course, like FakeBSOD.REG.
Syntax for REG Files
Just like you see in the example from above, all REG files must follow the following syntax in order for Registry Editor to understand them:
How to Import/Merge/Open REG Files
To “open” a REG file could mean opening it for editing or opening it to execute it. If you want to edit one, see the section above. If you want to execute the file (actually do what the file is written to do), keep reading… Executing means to merge it with, or import it to, the Windows Registry. You literally combine the contents of the file with the other registry keys and values that already exist. Whether your intention is to use the file to add, delete, and/or change one or more keys or values, merging/importing is the only way to do it. To merge/import it with the Windows Registry, just double-click or double-tap the file. This process is the same no matter the contents—a previously made backup you’re restoring, a registry tweak you authored, a downloaded “fix” for a problem, etc. If you’re sure that the file you’ve chosen is safe to add to the registry, then select Yes on the prompt that follows to confirm that that’s what you want to do. Depending on the changes that the REG file made to the Windows Registry, you may need to restart your computer.
