What is a Registry Key?

A registry key can be thought of like a file folder, just like any other on your computer, only these exist only in the Windows Registry.

Registry keys contain registry values, just like folders contain files. Registry keys can also contain other registry keys, which are then sometimes referred to as subkeys.

The handful of registry keys that exist at the top of the hierarchy in the Windows Registry are referred to as registry hives and have special rules attached to them, but they're registry keys in every other sense.

The term registry entry might refer to any individual part of the Windows Registry (like a hive or value) but usually it's synonymous with registry key.

Registry Keys in the Windows Registry

Let's look at a specific example from Registry Editor to help explain how registry keys work:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft

As you can see, the registry path shown above is divided into three sections- HKEY_LOCAL_MACHINE, SOFTWARE, and Microsoft - each separated by a backslash.

Each section represents a single registry key, with the right-most one nested under the one prior, and so on. Thinking about it another way: each key is "under" the one to the left, just like a path on your computer works, like C:\Windows\System32\Boot.

The first registry key, HKEY_LOCAL_MACHINE, is at the top of the path. If you remember from earlier in this article, that gives this key the special designation of being a registry hive.

Nested under HKEY_LOCAL_MACHINE is the SOFTWARE registry key. As I also already mentioned, you might refer to this a subkey but only in relation to the key above it - HKEY_LOCAL_MACHINE in this case.

The aforementioned Microsoft key is yet another registry key, of course, this one nested under the SOFTWARE key.

Registry keys can nest further and further down, too. Here's an example you'll find in any Windows computer's registry, and it's 5 levels down from the HKEY_CURRENT_CONFIG hive:

HKEY_CURRENT_CONFIG\System\CurrentControlSet\Control\Print\Printers

If you haven't realized already, items in the registry take on a structure like this:

KEY(HIVE)\SUBKEY\SUBKEY\...\...

... and, very often, contain one or more registry values.

See my How to Add, Change, and Delete Registry Keys tutorial for an overview of working with keys in the Windows Registry.

Backing Up & Restoring Registry Keys

Before you do anything in Registry Editor, backing up is a smart thing to do. With a copy of the keys you're changing in hand, you can feel safe doing whatever you need to do, knowing well you can undo them with a few taps or clicks.

See my How to Back Up the Windows Registry for details. You certainly don't have to back up the whole registry if you don't want to - just the registry keys you're messing with are fine.

Your backed up registry keys exist as a REG file and are easy to restore - just open that file and follow the prompts. See How to Restore Backed Up Registry Keys if you need more help.

Both of those how-to guides work no matter which version of Windows you're using.

Additional Information on Registry Keys

Registry keys are not case sensitive, which means they don't need to be written in upper case or lower case - they can be written either way without affecting how they work. This is probably only helpful to know if you're modifying the registry from a script or at the command-line.

Registry keys work the same way in all versions of Windows. There have been some changes in how you collapse and expand registry keys, but they were very minor tweaks and had nothing to do with their function.