Are Registry Cleaners Safe to Use?

People ask me all of the time if registry cleaning software is safe to use, and which one I would recommend. The truth of the matter is I don’t recommend using any of them! I did a video about this last year, with the help of some very knowledgeable people.

As most of you know, my assistant Kat is considered an expert in the field of malware removal and Windows security in general. In fact, she has been awarded the prestigious Microsoft MVP award four years in a row now. She’s been removing malware on huge sites like GeeksToGo for more than six years, and is a site administrator there. She also teaches malware removal in its free training program.

Over the years, Kat has helped literally thousands of people online to clean and fix up their computers. It’s something she has a lot of passion for, and is very good at. She answers questions like this every day, and recently posted a blog on Geeks about this very question. The information she posted is gleaned from her own experience with users, as well as many of the other experts she works with. I asked her permission to copy it here, so that more of you might be able to read her advice, and even add to the discussion.

Programs like CCleaner can be very dangerous to your computer. No registry “cleaner” is completely safe. There is also no hard evidence that “cleaning” out the registry has any effect on the overall speed of a machine. It will speed up searches within the registry itself, but has no effect on overall performance.

There are a few misunderstandings about the registry. People seem to think that “cleaning” the registry will make it smaller and easier to manage. Unfortunately, it doesn’t work that way. What you are doing is creating mini gaps in the registry’s file. These gaps will be reused by new data that inserts itself into your registry. The end result is that the registry becomes fragmented. Searching the data in a fragmented file is way slower than it is within an optimized file. In short, the only way to speed up the handling of the registry is by completely rewriting the file(s)… and even that is marginal at best.

Registry cleaning will not improve your system speed. Even though there are a lot of orphaned keys and/or values present, you won’t notice a difference in your system speed. The only difference you’ll notice is when actually searching your registry. Do you even ever do that? I know I don’t.

To be quite frank, if you “clean” your registry often enough, it will become fragmented. That will result in slower system performance… quite the opposite of what you were trying to accomplish in the first place. I think I’d rather have orphaned keys in my registry instead of deleting something by a so-called “cleaner” that should have never been touched.

That’s the problem with programs like these. They will miss entries that are “bad,” and mark good entries for removal. I’ve seen it happen hundreds of times over the years. A novice or “normal” computer user hoses their system completely, simply by deleting everything a program such as CCleaner told them to.

If you must do something with your registry, do it manually. If you don’t know how, leave it alone! You honestly never need to do anything in there. If you have a case of malware that attacks your registry, I urge you to seek help from someone trained to know how to properly remove it. Also, even if you consider yourself to be an expert on the registry, I beg you to take a few extra minutes to make a backup before you begin. I promise you’ll thank me later.

Last, I know there will be people who argue with me. There will be those who swear up and down that CCleaner is a wonderful program. They’ve never had a problem with it! Maybe you’re a tech who uses it in your line of work. Good for you! I’m glad you’ve never had a problem — yet. Even when you know exactly what you’re doing, programs like this still occasionally can and will completely hose a system. I sincerely hope it never happens to you.

credit to Sari and Bobbi_Flekman for some of the wording of this writing.

Kat makes excellent points in the above writing. I hope everyone will take the time to ponder what she’s written, and even add your own thoughts to the mix. If you’re using something like CCleaner to clean out your temporary files, stop it now. There are some excellent free alternatives that are much safer for your machine, such as ATF Cleaner or even TFC. Both are very safe, and very effective.

62 thoughts on “Are Registry Cleaners Safe to Use?”

  1. Good advice!

    There are a lot of ‘magic’ fixes and tweaks that get passed around on the web, it’s good to see these myths busted.

    One that particularly bugs me is when people suggest that you tweak your pagefile to improve performance… despite this persistent ‘help’ I have never, ever, seen benchmarks that prove this helps performance.

  2. This is a very good thing to know. I’ve used registry cleaners in the past like CCleaner. I thought it was safe, even though it asked you to backup the registry. I now know the consequences of these tools.

    Thank you.

  3. Hello,

    I have some more things to tell about registry.

    I also personnaly always said that registry cleaners are useless and dangerous.

    But one thing I do is defragment/compact registry hives using ERUNNT freeware so registry get rid of gaps and fragmentation.

    One thing also I encountered on Win2K machines (XP seems to have a much higher limit) is that SYSTEM registry is size limited ! if it goes up to 9MB (I don’t remember the exact size) then your system will not be able to start anymore and you’ll get black screen during very beginning of system boot when WIndows tries toload the SYSTEM registry file. You’ll get some “msdos” line showing an error 4 (if I remember well the number) with a stupid message telling some useless error text instead or clearly say ” SYSTEM registry too big”) so it took me a long time to find out the reason and finally found it on MSDN.

    The SYSTEM hive can grow a lot if you insert many USB devices and insert them in different USB Ports, especially with USB drives or memory as you can have many and also plug some other from friends.

    To clean such drive related entries and some other drive shre related (they will be redeclared as soon as you use them again) I use VxSCRUB that is also small, free and safe.

    Thoses 2 tools are the only one you need to “clean” you registry.

    But I remember the old microsoft’s RegClean back in 1997 ;-) It has been the only Registry cleaner I ever used years ago ! And it still works ;-) it do not clean many things but if you really want to use one, this one is safe.



  4. But what if you use CCleaner to make a back-up before it cleans the registry, and then use a registry defragger such as AusLogics’ Registry Defrag afterwards?

  5. I have been using for a couple of years now Registry Booster, from Uniblue. The only reason I went with this one was that it is Windows certified. Indeed, I have been using it without problems since I got it. Every time I run it, it deletes an average of 50 “bad” entries, or more.

    While I do understand the issues posted here, I can also say that I use Diskeeper, and it takes care of defragmenting the Registry (it is an option with Diskeeper).

    All in all, I think it is a good idea to clean up the Registry, although I wouldn´t go with any software of this type that wasn´t Windows-certified, for at least some peace of mind.

  6. Just to be precise, I just saw at the Uniblue site that the correct term is that Uniblue is a “Microsoft Gold Partner”, and Registry Booster is supposed to be “Windows Vista 32 Compatible”-certified. Or so I hope…

  7. I agree that registry cleaners are useless for speeding up the operation of a computer. However, what I have seen many times in my line of work is that a number of problems (lockup, seemingly freezes, programs constantly asking for installation CD’s, can’t unistall a program, etc.) that were solved by a registry cleaning. We use JV16

  8. I don’t know about CCleaner although I do use it. I primarily use RegScrubVistaXP which has a registry defragmenter built-in. I defrag my registry about once a month to eliminate said gaps. No problems in two years of using it. In fact, I once used it to fix little software popups that were occuring on my aunt’s machine and it’s been smooth sailing ever since. Personally, I’m quite happy with it. I use CCleaner primarily to remove tracking cookies.

  9. At work I am using regseeker to clean-up DCOM problems, DLL, OCX registration and other related information saved in registry.

    There are some application that do not clean themself up after uninstall.

    So the procedure I use is delete all files related to the apps, delete the entries in dcom config and then run regseeker cleanup to delete all parents and child registrations.

    This way the machine is clean an a re-install of the apps will work.

    I have been using this procedure for years without any problems.

  10. To quote your line “Over the years, Kat has helped literally thousands of people online to clean and fix up their computers” indicates how bad computer hardware and software design really is. The only resaon a computer should go in for repair is due to componet failure. If the OS was programmed properly we would never need to make decessions on which AV or repair program to choose from. All they “Microsoft’ & “Apple” have succeeded in doing is create make work projects. Chris had this happened, you would probable not be in this line of work. Hard to imagine.

  11. I think it is fair to point out that CCleaner only cleans out the registry when you specifically tell it to, and in compirson with ATF or TFC it is equally as effective in temp file clean up. Agree?

    That said, let me clarify….ATF rocks, I use it over ccleaner anyway :P

    Excellent article! The same goes for programs like revo unistaller that allows you to remove registry foot prints.

  12. Agreed, Registry Cleaners are rather dangerous.

    I foolishly used on the other day, and 2 apps were immediately broken, requiring installation.

    There were other problems too. Out of curiosity I re ran the reg cleaner (PC Win Doc Pro) immediately afterward and it found 80 more “problems”.

    The question is, why didn’t it find these ‘problems’ on the first pass?

    As for the speeding up windows, ‘cleaning’ the registry would never work. It’s a database – removing entries does not shrink a database.

  13. wow… this has opened my eyes up big time. i never knew that cleaning your registry can actually fragment it! i think when people ask “how can i speed up my computer” people will respond with: get more ram, clean your hard drive, and clean your registry. thank you so much for this article, but i have a question about CCleaner, i use it, but not to clean my registry, i use it to clean my temp. files, and the other things it does, is that safe to use? and i have one more question, i have win 7, and have the sidbar app to calculate ram and cpu usage, and when my system is not doing anything, just sitting at the desktop, i am using 1.5 – 2 gigs of ram. is this normal, when i had vista, it was like 2 – 3 gigs at idle, but is this normal? oh and congrats to your assistant!

  14. Hi.. I am just wondering, the whole article is about cleaning registries, and then at the end it is said to not use Ccleaner to delete your temporary files?
    Ccleaner has multiple uses, one of them is to clean the registry, and another is that it deletes unneeded temporary files from your computer. These are 2 different things, so why should we not use it to delete temporary files from our computer? as cleaning temporary files, and cleaning a registry are two different things.

  15. I have used Registry Mechanic during the last four years.
    I run the app every time I delete a program (with their own uninstaller or with windows´one. That and a regular defragmentation (weekly) keeps the start up and shut down times at the original level.
    Thanks for your informed opinion, Ms Kat!

  16. I whole-heartedly agree with you. As a professor of an A+ course, my students are always asking me what I use to clean out my registry. When I tell them that I don’t use anything, they are shocked.

    As Kat stated, there is really no need to deal with the Registry unless you’re fixing someone else’s mess-up for doing so in the first place.

    Great advice, Chris and Kat! Keep up the great work.


  17. I can personally attest to the fact that registry cleaners can hose a system. I’ve seen it happen. Remember, people, you have a program going in there and removing things. How often have you looked at what it’s removing before hitting the “next” button? I know it’s tempting to use these programs thinking your going to save some precious milliseconds. And it’s true, installing and uninstalling applications does leave little bits of refuse behind in the registry. But, like Kat wrote, you are not going to save that much time if any by “cleaning” the registry. You are better off defragging your hard drive and deleting the couple of gigs of “asian models” you have stored and freeing up some hard drive space for other uses.

  18. I worked for Microsoft in the 90s as a Senior Technical Writer. Among other things, I heavily revised the MS-Press book on the registry and wrote the Registry Help File for the Resource Kit. In my opinion, you should never ever use a registry cleaner. CCcleaner and jv16 PowerTools 2009 are excellent tools for OTHER purposes. All of the registry cleaning tools I have ever tried out give as many as 100s or even 100s of false positives. Some of the best sellers in that category don’t even give you a choice. After a scan, it’s delete all or nothing. Frankly, they all present a long list of either harmless or actually important keys and values. if you use one of these cleaners, don’t be surprised if some Windows functions disappear or programs don’t work properly. leave it alone. Windows knows what keys to access and usually does it appropriately.

  19. I fell for many of those registry cleaner come-ons that scan for free and you have 413 problems that can be fixed but only 10 for free then you must purchase. I foolishly thought that if I use enough of the free 10 cleans, eventually I would get a cleaner registry. Then RegCure offered Lavasofts AdAwarePlus as a bonus with purchase for less than the cost of AdAware’s normal premium package price.
    What I got was RegCure will find 413 problems and say it fixed all of them. Rescan and you mysteriously have 627 new problems. Good news is RegCure can fix all of them also.
    Rescan and you have 329 new problems.
    Every subsequent scan finds over 100 new problems. How good can a fix be if you get more problems identified by the product than you started with?
    I dumped it fast and dove into the registry manually to ferret out each new entry compared with my backup.
    Ended up going to Win7 soon after and nothing that can identify the abundant google trojans is compatible anyways. Had to say goodbye to my trusted friends; ZoneAlarm,Norton,Spybot S&D, and AdAware as they will not allow Win7 to run. More on that in a soon blog post.

  20. What makes cCleaner bad for temp file deletion? the whole post was about registry cleaning, then you throw in that vague flaming statement with no proof?

  21. For those of us that have been using CCleaner for several years– I assume from your comments that my registry must be full of holes and jumbled entries. Do you recommend that I use a “registry defragger” to correct this problem? If you, do your recommend a particular one?



  22. Finally someone with a little sense in their head. The registry is not a amateurs playground. I see customers in my store every day that do just this and accidentally delete a key that controls a vital boot function. However there are a limited number of tools that make direct changes to the registry that in the enthusiast community are absolutely essential. For example RivaTuner and EVGA Precision both make changes to fan speeds by editing registry keys and because the term automatic fan speed often equates to slowest fan speed in all scenarios, it is a necessary evil specially in instances where overclocking is considered.

  23. I do agree that most registry cleaners are over-rated to solve most system errors which is not always correct. Other methods like the Comand Prompt ” chkdsk /r ” and System Restore should always be used first to fix system errors. I have been a computer tech since the days of Windows 95 and have a BA in computer programming and I will say that sometimes when Registry Cleaners are used correctly they can solve some problems. Mostly application related errors. I feel that this article used a very bad example of a registry cleaner, CCleaner is basically a system junk cleaner not a registry cleaner. It only cleans the most safe errors of the system registry. CCleaner is constantly getting updated all of the time and runs on all versions of Windows. ATF Cleaner and TFC are both very much out-dated and lack many settings and user control. I’m surprised that this article recommends these out-dated programs that don’t even support Vista. I will say that I have used CCleaner for many years on my systems and my customers systems and never once has it ever caused any problems and if you read most of the computer help forums they all highly recommend CCleaner. The example that this article should have used a a dangerous registry cleaner should have been RegCure, it is the most popular registry cleaner and it is complete junk. It deletes many needed registry keys by default.

  24. NO; Registry cleaners are not effective.

    I’ve fixed a dozen or so computers on which registry cleaners were run.

    I’ve never run one on my own systems. My systems have not taken a performance hit because of not running a registry cleaner. That includes an XP system that has been running for 7 years without any problems.

    Given that, is there a reason to run a registry cleaner? No.

  25. So you actually charged people to fix registry issues, when you could simply have advised them to use the backup feature that is in all of these programs, including the dreaded CCleaner…

    Come on people, this isnt that difficult. I want crap off my PC that I don’t need any longer. It is that simple.

  26. Registry cleaning freewares are available online and the users have to download it to their computers to clean their registry. After downloading the appropriate version of the registry cleaner that is suitable for your OS, the program has to be installed into the system. Installation process is very simple and is less time consuming. For Windows XP users, the need to reboot the system after installation is absolutely not needed. By running the .exe file placed on the desktop, the program will be launched without delay.

  27. have had trouble in the past with my windows registry. I have messed around it myself because I though I could fix something simply. I ended up crashing the computer. I had a hard time even getting to my restore points to restore to a previous session. Now I use a competent windows registry cleaner to help navigate my windows registry.

  28. I was told that Cc cleaner was safe. I was skeptical. Now I have learned to go on my instincts..I have been burned, bad by Regicure. (or however it’s spelled). Never again it was an utter disaster.

  29. I almost used registry cleaner, as recommended by best buy’s geek squad. After reading here I’m glad I didn’t. I have windows xp and my screen saver stopped working. It used to work if I would go to personalizations under control panel and click on apply and ok again, but now even when I do that it won’t come on at all. Any advice?

  30. Registry cleaners are not “cleaners”, they’re simply arbitrary key deleters. You get no performance benefit out of it whatsoever, so if you have no application issues, what’s the point? If you have an issue with an application and half a brain, you should go in and fix the problem manually – the proper way to do it, not a Neanderthalic “Durrr, delete everything and hope the key is recreated with the proper value” shotgun approach. The greatest part is when people reboot the computer once, think it’s fine, and commit the changes, then wonder why, in a few days when a program tries to update or a peripheral’s device driver is loaded, Windows BSoDs. Oh well, it brings me a lot of business to fix the issue.

  31. wow. i was really paranoid to have my registry defragged but actually knowing it was useless! thanks! i really needed to know that!

    and the sad thing is i use ccleaner’s reg cleaner everyday. :(
    so i never really need to defrag my regstry?

  32. If you are aware of registry keys you can manage it manually but if you aren’t very skilled with computers, there is a big risk that you could damage some data that is important to you . A registry cleaner will do it automatically for you – eliminating the junk, but leaving in everything important. I am using PC Optimizer Pro . It’s a gud registry cleaner.

  33. A registry cleaner will automatically eliminate the junk, but leaving in everything important. They’re usually pretty cheap, I m using PC Optimizer Pro a gud registry cleaner.

  34. Commercial registry cleaners have one primary purpose – to transfer money from your bank account theirs. They are quite good at doing this. Of course when you enter into such a transaction you expect to receive something of value in return. Registry cleaners fail to deliver.

    The problem with registry cleaners is that it is rarely possible to be 100% certain that a particular registry key or value is unnecessary or bad. So they are forced to guess. Most of the time they guess correctly, but sometimes not. Then you have a problem.

    I read of a controlled experiment where the registry of a computer was bloated with vast numbers of unnecessary registry keys and values. This was to a level far beyond anything that would ever happen under real world conditions. The impact on performance was barely measurable.

    I recognize that a registry cleaner has some value in solving a specific problem when used by someone who understands the registry and the limitations of these products. Most computer users have nothing more than a vague idea of what the registry is. In such hands a registry cleaner is dangerous.

  35. you can get your problems solved if you use tuneup360, i’ve been using it for several months and found it really helpful

  36. i use a registry cleaner everytime i uninstall programs or delete something.. i think i will never do that again.

  37. After having used System Mechanic for a year, I understand such a tool is unnecessary at best and dangerous at worst.
    I deactivated then uninstalled and manually removed reg. entries re System Mechanic a month ago, I perceive no slow down in the performance.
    System Mec. would tell lies as to the cause of internet outages, when I had verified they were the service provider’s problems, and claim credit for having restored internet connection.
    Also, it would claim registry errors and a few theatric action, declare cleaned registry when I had not used the PC after the last session.

  38. I have used registry cleaners allot in the past way back in the xp days, mainly ccleaner, I myself never had any problems with using registry cleaners but in saying that I never noticed any performance gains either.
    I don’t use reg cleaners anymore, haven’t for some years now no reason just don’t, I never understood how a reg cleaner would give any performance anyway, one sales pitch a reg cleaner site will give you is uninstalling an application will leave unlinked and broken registries witch will slow down your pc because it will have to search through your reg and find the proper one such and such(in different words) well that’s crap ya open a program or what have ya and it goes straight to the entry doesn’t search for it, its like if I open a program with command c:\program files\fatty\game\game.exe it knows were to go and starts it, it does not search the hard drive for it. sorry i am not good at explaining what i mean lol. If reg cleaners are risky and gain you no performance why has microsoft got it bundled with live care and microsofts safety scanner?

  39. The registry cleaner in CCleaner is a tool that shouldn’t be used, but the Cleaner function is fine, and that is what I think most people use it for primarily (I could definitely be wrong, I’m not privy to those kinds of usage metrics, nor have I seen any online). It does exactly what it says, and clears the contents of folders and logs that could be taking up significant space on any given system.95% of computer users have no idea what a log file is, and will never know, and will never need them. I’ve never had a problem with it deleting something that causes a break in my system, using the standard Cleaner function and not the Registry cleaner. I also run several systems without virus protection and enjoy the challenge when I actually catch something, so I may not be the best example, but the point should still be valid.

  40. of questionable use, seem to have read the same item word for word on another website,
    THEREFORE your credibility is ZERO.

    One can usually rely on sound advice if you take money out of the loop

  41. I hope I’d read this article sooner :( Before I everytime checked what does CCleaner delete in the registry, and if it was something about a program I knew I deleted then I let it go. This time I was lazy to check what it does. The next day – Startup Repair came up and said an error occured and it can’t be automatically fixed, so I had to reinstall my Windows. Geez that thing sucks!

  42. Don’t worry about registry just worry about vendors offering products at the end…

  43. Ccleaner works, if it works it works- it is noticeable, period. Faster is faster , simple as that. When removing a problematic program, there is no way to get a clean instalation until you remove the file and clean temps. Anything else is non-sense.

    Besides, this article goes striaght againts that particular product not mentioning Regclean, Regseek and others more. Zero kudos!

  44. On one of my computers running Windows XP, BoostSpeed’s registry cleaner caused Microsoft Office to have multiple problems, so I had to re-install Office. Tried it twice just to make sure that’s what did it. It was.

    On my Dell D600 laptop running Windows XP weeks ago, BoostSpeed’s registry cleaner somehow disabled both of my right-click buttons next to the touchpad. After much Googling, I still haven’t found any fixes that work, including re-installing drivers, making sure the touchpad settings are correct, etc.

    The only workaround I found was to set the upper-right corner of my touchpad to emulate a right-click.

    If I go into touchpad settings and tell it to swap left and right buttons, NEITHER work, and Enter no longer executes a menu option! Do you know how hard it is to run the mouse configuration when neither button is working, and Enter no longer executes anything? I finally found the CTRL keys that would select the Mouse driver in the Control Panel, but don’t remember what it was.

  45. Dear Chris,

    I’m also puzzled about the registry and have never understood how to maintain it or keep it from corrupting my system somehow.

    I’ve recently had a very frustrating email exchange with Mihal Roman from Spamfighter. Firstly he told me that they have no intention of fixing the bugs and various flaws in the antispam software, saying that this is how the software is intended to work and there’s no need to improve it or release any bug-fixes in the future. It’s good enough, he claimed. (I was complaining about spam emails that weren’t being blocked, despite my marking them as spam and adding their addresses and domains to the black list). He then said it’s perfectly OK for the Spamfighter software to use the registry to store and maintain the black and white lists.

    Is that right?

    It means that every time I receive email (and I get around 1,000 emails a day), Spamfighter is writing to the registry.

    Isn’t there a risk of corrupting the registry (particularly if there are outstanding bugs and security holes in the software that aren’t being maintained)? I would have thought that the registry needs to be backed up before any major changes (like installing new software). But if the registry is being used as a private database file for an application then almost anything could cause a serious system crash – maybe something as little as a power failure in the middle of receiving emails and/or marking an email as spam or not-spam.

    Should I be worried? Should I uninstall Spamfighter?

  46. This is a completely biased article against CCleaner and I disagree with her opinion on registry cleaning, the OS loads up the registry at startup, the smaller it is, the faster it’ll load, plus, CCleaner gives you the reason why each registry key should be deleted.

  47. I’ve done a test by programatically adding all sorts of stuff into relevant registry roots, increasing the size of it by at least 20%. The performance change was insignificant so I really don’t see a reason to screw up your system for 0% increase in Windows startup. Besides, a typical “bloated PC” has a registry size of just over 350MB, for $29.99 you can buy extra 6 gigs of RAM rather than some registry cleaner. In this time and age I don’t see a reason to risk anything over saving extra 50MB of RAM (which would be a LOT of registry junk).

  48. I just had a very bad experiance of systamtweak cleaner , I Only ask to Clean deep into my hard driive c, after IT finished The computer had Drive D instead of c & when I click on it shows d with few files S when I opened the recovery , there was no other dates so i could not back date on this recovery ,then I realised these cleaner are pain in ass I straght away wanted the refund ,but they have very complecable way of refund sys.

  49. Auslogics makes a Registry Defrag program; I’ve heard that they’ve won awards for their Disk Defrag… Is a Registry Defrag safe to use? Seems like it might be a good thing especially after having messed around with a Reg. Cleaner..?

  50. I know that this post was written “5 years ago” so I hope this will still reach you. I bought Auslogics BoostSpeed 6 yesterday because it boasted some pretty great stuff, but after having read this article and several discussions on the Microsoft forums, you are the first person (who seems to know what they’re talking about) that has said anything good about these types of programs. All of the Microsoft guys said that registry cleaners don’t actually benefit you and will inevitably screw up your system at some point… I guess everyone has to go to college for this stuff if they want to know anything for themselves. So hard to find consistent answers about this stuff…

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