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Nick Lewis is an editor at How-To Geek. He has been using computers for 20 years — tinkering with everything from the UI to the Windows registry to device firmware. Before How-To Geek, he used Python and C++ as a freelance programmer. In college, Nick made extensive use of Fortran while pursuing a physics degree.

Nick’s love of tinkering with computers extends beyond work. He has been running video game servers from home for more than 10 years using Windows, Ubuntu, or Raspberry Pi OS. He also uses Proxmox to self-host a variety of services, including a Jellyfin Media Server, an Airsonic music server, a handful of game servers, NextCloud, and two Windows virtual machines.

He enjoys DIY projects, especially if they involve technology. He regularly repairs and repurposes old computers and hardware for whatever new project is at hand. He has designed crossovers for homemade speakers all the way from the basic design to the PCB.

Nick enjoys the outdoors. When he isn’t working on a computer or DIY project, he is most likely to be found camping, backpacking, or canoeing.

Registry cleaners have been available for decades, and once upon a time, there might have been an argument for using them. However, these days, they present almost no benefit and could mess up your PC.

What do registry cleaners do to the Windows Registry?

The Windows Registry is basically a long list of settings. It specifies what options are enabled in Windows, what values some settings take (like whether Windows in in light or dark mode), specifies where programs or assets can be found, and countless other things.

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When a program is added, new registry entries are created and old ones are often modified. After several years of use, it isn’t uncommon for the Windows Registry to have a bunch of old, unused registry entries from the various programs you’ve installed.

Broadly speaking, registry cleaners go through the Windows Registry in search of those abandoned registry keys in the hopes of saving space and "increasing performance."

However, even a massive registry that has been left "uncleaned" for a few years will only measure a few hundred megabytes in size. Given that modern storage drives are measured in hundreds of gigabytes or even terabytes, wiping out a small fraction of the Windows Registry—which tops out at a few hundred megabytes in the first place—there is no chance that cleaning the registry is going to make an appreciable difference in your available space.

A few programs will produce abnormally large registry entries that can drive the size up into the range of a few gigabytes.

When old computers used mechanical hard drives as their boot drives, it is conceivable that a large registry could have slowed down a PC a bit. However, even SATA SSDs, which are much slower than their NVMe-based siblings, aren’t limited in the same way.

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What registry cleaners do wrong

Because of how integral the Windows Registry is to the stability of the operating system, deleting things haphazardly can seriously mess up your PC. In a worst-case scenario, it can even make it unstable or inoperable, forcing you to use a registry backup.

This is where registry cleaners can cause problems. On more than one occasion, I’ve had a registry cleaner get a bit overzealous and start deleting registry entries it shouldn’t.

If it stopped at deleting settings it might be just an annoying inconvenience, but it doesn’t. It completely deleted registry entries related to programs I had installed, which rendered them completely inoperable until I reinstalled the program.

In a worst-case scenario, a registry cleaner could erroneously remove a registry key related to something important to Windows. This is most likely to occur after a major Windows update. Depending on what it deletes, it could cause serious issues for your PC.

Considering the risks involved, and the fact that there is little to no potential benefit in the modern era, you’re better off staying away from them completely.

What if I need to clean my registry?

In all likelihood, you actually don’t need to clean your registry. Unused, abandoned registry entries take up almost no space, and they don’t normally interfere with the operation of your PC.

There is one noteworthy exception that I’ve run into, and that occurs when an old registry entry for a program later makes it impossible to reinstall the same program again at a later date. This usually happens when you manually delete a program’s files rather than using an uninstaller, which should clean up the registry automatically.

In any case, what you need in this situation is a scalpel for the registry, and a registry cleaner is more like a chainsaw.

If you do have a program that won’t reinstall because of a problem with the registry, what you need to do is open up Registry Editor, use the search function to find the places where that program exists in the registry, and then delete or modify only those entries.

Once you’ve done that, you should be able to reinstall the program again without an issue.

There are programs, like Revo Uninstaller, that can selectively clean up the traces of a program from the registry without requiring that you go through it line by line.

I still recommend against Revo Uninstaller generally, since it shouldn’t be necessary. However, if you do definitely need to remove the remains of a program’s registry keys, it is an easier and likely safer approach than clearing the registry manually. It is also less likely to cause problems than a general registry cleaner as long as you don’t go wild on its most aggressive settings.

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Registry cleaners aren’t generally useful anymore, and the risks they pose far outweigh their potential rewards—which are negligible. And remember, if you want to get rid of a program, use the actual uninstaller instead of just deleting it. That’ll cut down on the number of random leftover registry keys.

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