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Is it Safe to Delete Duplicate Files?

Question: Is it safe to delete duplicate files found by duplicate file finder programs?

I’m going to get some flack for this , but my answer is yes, followed by a very strong NO.

Let me explain why.

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Because installing software in Windows is complex, it’s common to have duplicate copies of the same file, all of which are required. Sometimes you can delete duplicates safely, but it requires knowing how your files are organized — something duplicate file finders can’t do. Duplicates rarely take up excessive room. You’re best served using different techniques if you’re running low on space.

Installing is a mess

Duplicates? Or not? Needed? Or not?Over the years, software programs have gone from attempting to share large numbers of components to keeping separate copies of those components to protect themselves from unexpected changes.

As a result, today some files are shared and some are not, and there’s no consistent rule.

Let’s use an example.

A versus B: fight!

Program “A.EXE” (A) and program “B.EXE” (B) both rely on a large library of mathematical functions we’ll say are contained in the file “STATS.DLL”.1

Scenario 1: shared

Installing A installs STATS.DLL such that any other program can use it. When you install B sometime later, it sees STATS.DLL is already present, and does not install it a second time.

Sounds fantastic, since disk space is saved and there’s only one STATS.DLL to keep track of.

Updating STATS.DLL updates it for both programs A and B. Put another way, an update to A that includes an update to STATS.DLL updates it for B whether or not B needs it, wants it, or B works with the new version. If B breaks because of this unexpected update, you’re stuck until B is updated to work with the newer STATS.DLL. Sadly, this happens often.

If B is never updated, you’re screwed. Sadly, this, too, happens often.

Scenario 2: duplicates

Installing A places STATS.DLL into a private location where only A can use it. Later, installing B does the same, placing a second copy of STATS.DLL for only B to use.

When A is updated, it only updates its copy of STATS.DLL. B is unaffected.

You have two copies of STATS.DLL on your machine. In fact, you may have two identical, duplicate copies of STATS.DLL.

But deleting either one would be a big mistake: deleting A’s copy would break A and deleting B’s copy would break B. You need both copies, even if they are duplicates.

What you can delete, maybe

It can be safe to delete some of the duplicate files your duplicate file finder identifies. For example, if you have duplicate copies of photos on your machine, you may need only one.

But which one? If you’ve organized your photos in a folder, and a second copy of an image happens to be elsewhere, which one will the duplicate file finder delete? How does it know which one matters?

It doesn’t.

Even if you restrict yourself to certain file types (only look for duplicate “.jpg” image files, for example), you still run the risk of deleting images that were installed by multiple programs you use — if both program A and program B happened to install “smiley.jpg” as part of some kind of resource library, how do you know whether either can be deleted safely?

You don’t.

It’s just not easy to tell what is safe to delete. Without knowing, it’s quite possible you’ll break something — sometimes immediately and sometimes in ways you won’t discover for some time.

My advice: don’t.

When in doubt, don’t delete

If you insist on deleting duplicate files, I strongly suggest you take an image backup first, in case it turns out I’m right and something breaks.

But I really recommend you don’t go down this path to begin with. Don’t bother looking for duplicate files.

Instead, if you’re trying to free space on your hard drive, use tools that show you where the most space is being used, and target your efforts there to get the biggest bang for your efforts.

But in general, unless you know what you’re doing, leave duplicate files alone.

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Footnotes & References

1: A “.EXE” file is an executable program. A “.DLL” file is a Dynamic Link Library of software typically designed to be shared among multiple programs. (DLLs need not be shared; sometimes they represent nothing more than structural organization.)

36 comments on “Is it Safe to Delete Duplicate Files?”


  2. I got a call from a guy who couldn’t get MSN Messenger to run. I couldn’t either even after reinstalling it. Also I noticed the adware program wouldn’t run. I downloaded that version and even that wouldn’t run.

    An antivirus scan showed no infection. The only clue was when trying to run Lavasoft Ad-Aware it wouldn’t but there was a error message concerning the file RICHED20.DLL. I assumed it was corrupted/missing – did a search and found 4 instances of the file on the computer.

    I decided to download a new copy of the internet. They didn’t have the install CD and I wasn’t sure about the copies on the system. After downloading I wasn’t sure where to put it. I chose SYSTEM32 folder even though there wasn’t a copy there. Problem solved.

    I had a similar problem with WMP.DLL from Media Player 10. Found 4 instances of the file on my hard drive and decided to use one of them. It worked by coping the file from one folder (can’t remember the name right now) to the SYSTEM32 folder where again the file was missing. It worked. Duplicate files aren’t always bad.


  3. For some now, I ‘ve, almost religiously, been running CCleaner, then Disc Cleanup, then Drive Cleanup before turning off my computer. I wanted to know how it looked once, so after performing my usual shut down cleaning, when I next turned it on, I ran the same programs. There’s a surprise. It seemed that all those nasties (or most of them at least) were back. I had done no surfing, no going on online, nothing. What’s going on here? Am I wasting my time doing these chores?

  4. I’ve learned this lesson the hard way. Once I ran one of these duplicate finders to clear up some duplicate files (lean = fast, right?). When I got done ALL of my shortcut files had disappeared. My desktop was blank, my start menu was blank, my quick launch was blank. I’ve decided since then that duplicate files aren’t that bad….

  5. I agree that deleting duplicates files could be a problem IF you’re not looking at the duplicates before you delete them. Checksums are important when integrating it into a duplicate file program.

    Also, I’m still wondering how someone could lose their operating system without knowing it before they click…….hmmmmmm

  6. As Leo and many other in this thread says it is not safe to remove all duplicate files. I would recomend only to remove user files (digital photos, music, documents etc) and carefully check every file before removing it and not use any programs that automaticaly removes clones without your control. The problem is not only to find the duplicate files but to select which ones to remove.

  7. Well Leo, You shot me down…sorta. I discovered your site while seeking an efficient solution to a duplicates problem (some unknown application or some action on my part has resulted in vast numbers of duplicate files, primarily shortcuts, on my Vista system. It would take many hours to remove them all individually). My problem is not primarily a duplicate program removal issue, but you have convinced me to be extra cautious. I have encountered problems such as you describe in the past, sometimes with disastrous consequences. Thanks for reminding me of the potential problems.

  8. hi leo,

  9. Wish I had read this like 3 days ago. Downloaded a duplicate file finder, one highly rated by all review sites and consumer reviews. I did some duplicate file removing for a couple of days without a hitch. As confidence grew I decided to give it a real workout and check Windows and all it’s subfolders for duplicates. As you can imagine there were over a thousand duplicates listed, some with five duplicates of the same file, or so I thought. Diligently began checking file against file, tried to get an answer as to which would be safest to delete, ie oldest, newest, longest, shortest, but found no information. Remembered that a program from Toni Arts suggested keeping oldest files, but I have been messing with this computer for so long it didn’t help much. I told program to keep all hard links from being scanned and thought now I could go to it. Well here I sit 3 days and a gazillion hours later and am just now able to use the computer again. The questioer asking about couldn’t I see operating system and stuff was being taken, of course not. I wasn’t even deleting the files just sending them to recycle bin temporarily keeping location information with each file. Guess what, started the process and about three minutes into it the screen went black, computer tried to reboot and repeatedly tried to reboot until I stopped it. Could not run any of the boot options like safe boot or last good startup, nothing. Just kept saying starting Windows than shutdown and restart. Had to use Windows CD to try and start computer, but it couldn’t repair my Windows installed on computer and had to load a new copy of Windows to the computer. Three days later I am happy to say everything is back to where it was prior to my trying to get rid of some stupid duplicate files. Guess Stupid is really what Stupid does, eh? Word to the wise, unless you are single, jobless, and bored; live with the duplicates and buy an external hard drive if you want quick extra disk space. Worth the money, but more importantly worth not having to go through the frustration and time of all the above.

  10. To quote the tuna fish commercial, “Sorry, Charley.” :)

    Folks, Leo has said this MANY times before:

    BACKUP your &@^($% computer before trying anything so radical! (Like, “Duh…?”)

    I use BootItNG, and I would make a full backup before doing anything like Charley did. It boots up before Windows does, and saves its files to an external drive, so if need be — and provided only that the C: drive itself is still physically intact — I can restore my computer to its full pristine Before-Disaster-State even if my entire Win XP Pro operating system is completely hosed.

    It’s the best insurance you could ever have, folks: an External Drive, BootItNG, and You. Mutato nomine de te fabula narratur.

  11. I agree with the poster who advised buying a large disk. Disks have long been cheaper than lost files. Also, get an un-deleter program. If you un-delete before the deleted file’s disk blocks are re-used, you can save much grief. I’ve used Vcom’s Fix-It un-deleter a couple of times in the past few years, much to my relief. And please excuse my repeating the often-heard advice “BACK UP YOUR DISKS!” If you have a machine reserved for hacking, back up a full-disk image from your real-work machine, and then restore it to the hack machine, to be sure the cycle works. Then delete files from your real machine, if you like stress and hassle.

  12. If it’s space you’re looking for and duplicate files in your windows directories is the problem (especially dll’s) a “clean install” is your best bet if you want to avoid headaches :)

  13. I agree with keeping out of system files and application files but I do need a streamlined setup for sifting through would be duplicates or candidates of redundant files.
    For finding my duplicate files I like to have open on a large monitor a folder where each file is located(A original, and B…Z possible backups/redundant files).
    I like to display as much info as possible but sometimes I compare folders and have not been able to display the size of folders without pressing Alt + enter(properties). There is other info I would like to see in order to more quickly glance at attributes and thumbnails to compare.
    However, had I set out to organize user-made files into something like follows, I wouldn’t have these problems: 1)Main hard drive, created file
    2)backup(sequentially, noting date of amendments or revisions, deletions, moving, et cetera
    3)reference for further organization, such as topics of commonality(use shortcuts??)


  14. You can try this FREE tool that was recently featured on PCMagazine and ZDNet it has protection for system files: – Fast Duplicate File Finder
    Fast Duplicate File Finder will help you find fast all duplicate files in a folder and its sub folders.
    The applications will compare the content of your files so it will find duplicates even if they are using different file names.
    It uses fast binary comparison algorithm and has internal preview supporting a lot of image, video, music and text file formats.

  15. There are some programmes for XP to find duplicate files. I wanted to delete music duplicate file I used the programme Delete duplicate files for such aim. It helped me. This program is not only for the music, but for all files. And now it is more free place on my PC :)

  16. help – since deleting all my duplicate files through software I downloaded I have no start bar or icons on my desktop. I suspect, I’ve done more damage than that. The only way I can get online is through taskbar. Is there anyway to restore my computer to the day before I did this. I can get into dos through my taskbar. I am away and cannot get to my original Windows XP discs. Thanks, Jf

  17. Ever hear of “backups”? I often intentionally place duplicates of important files in several places, so that if one is corrupted in one place on the drive, I have another copy.

    Not all duplicates are “evil” even when their removal doesn’t break anything.

  18. I’m with you. Deleting dupes takes thought. The first thought being, MAKE A FULL BACKUP BEFORE STARTING!

    Second thought, NEVER, EVER, run a dupe finder in auto delete mode.

    Third thought, stay away from system files/folders.

    Next, be very very careful when deleting application related files.

    Next, deleting dupes is safest when dealing with user files, until you delete the wrong copy of one of your data files.

    Finally, when in doubt, DON’T DELETE IT!

    Instead of deleting dupes, I often use Windows file compression on Folders for apps that I don’t use often.

    One place I do find dupe finder tools handy is when apps install support for multiple languages that I’ll never use (ie help files, EULA’s etc). The files typically have the same name even though the contents are in different languages. Them I gladly nuke (and search for folders with similar names, typically 4 digit numbers). Granted, they don’t amount to much space freed up, but they also represent larger blocks that are freed up. I’ll take any advantage I can get.

  19. Yeap. That is PRECISELY what I dislike in Windows, the lack of modularity. The original IBM PC’s modularity was, in great part, the reason for its success. (You had a barebones box and just plugged into slots whatever you wanted / needed.) Windows sneaked into prominence in spite of being built on the concept of interdependence. Anything you install or anything you uninstall can make changes to the Registry (what I call the cancer in Windows) and remove modules needed by other programs causing anything from annoying messages to a total inability to run Windows or some other program you own, totally unrelated to the one you installed or removed.
    Incidentally, this explains why most Windows programs cannot be just copied from one machine to another by just copying the directory. If the developer chose to use the Registry or shared modules, (amazingly, most do) the program will not work. Also explains why you generally cannot remove a program from Windows by just deleting its directory either. For one thing, you may leave all sorts of trash in the Registry and / or shared modules area.
    Every release that has come since Windows 3.1, I have hoped to see a move away from this complete interdependence but it has yet to happen.

  20. PLease advise I appear to have hundreds of duplicate GIF Images, for example: at least 20 of the following: cf2_09-03 32.6 KB (33,445 bytes, Toshiba Configfree Gif Image, there are many more, can I delete the duplicates? thank you. Kind Regards

  21. I’m with you. Deleting dupes takes thought. The first thought being, MAKE A FULL BACKUP BEFORE STARTING!
    Second thought, NEVER, EVER, run a dupe finder in auto delete mode.
    {URL Removed}

  22. “I use DuplicateFilesDeleter Program in my pc to speed up my device by removing duplicates files, photos and videos etc.

    It is an amazing tool with powerful feature”

    • The same warning in this article applies to using a duplicate file finder. Those programs don’t have a way of determining which duplicate files are redundant.

      See the first comment to this article. The commenter said using a duplicate file finder broke his installation of XP. This could happen with any OS.


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