I have File History set up on my Windows 10 PC to save copies of my files to a network drive every hour. As I understand, it's supposed to only save those files that have changed since the last time they were copied, but it looks like it's copying all files, essentially creating a full backup set of all my files every hour.

Here's an example of a Word document in my OneDrive documents folder:

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As can be seen, the file was last modified in January 2014. Yet File History keeps saving a copy of it every hour (except when the PC is off, of course):

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That's just a selection, in total I have 53 identical copies of that file. Of course, it's pretty small, but the same is happening with e.g. video files hundreds of megabytes in size. The result is that File History is quickly eating up the space on my network drive.

How can I fix this? Is it a known bug with File History in Windows 10? I've searched online but haven't found any solutions, or even any descriptions of the same problem.

  • If you were to run Sysinternals' Process Monitor and filter the log by the path of that document, could you post the log of events occurring in a 1 hour time period? – int_541 Apr 15 '16 at 6:42
  • Hi there, It is a pity that this problem is still hitting W10 users. I am in the W10 Insider slow ring, using W10 2004 19041.84 version and this bug is still there. I installed github.com/nvm-sh/nvm in my $HOME folder that is handled by FH and I ended up with 150+ copies of this folder that has never changed in FH, that is 1500000 files and about 70Gb! Same with stuff I downloaded from the net. So FH is still unabled to detect correctly when a file has changed. – FabPop Feb 22 at 9:45

This problem of duplicates has always existed since File History was introduced in Windows 8.

For some people the following solution has worked :

  1. Control Panel -> System and Security-> File History -> Turn off
  2. Settings -> Update & Security -> Backup -> More options -> Stop using this drive
  3. Delete the File History folder in your external drive.
  4. Start using File History again.

For others, the above solution didn't work. If you are one of them, you should consider a third-party solution. See the article Best Free File-Based Backup Program for some suggestions.

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  • Read the the sentence after the posted solution: "After these steps, I can add folders to "Excluded Folders" and they remain excluded." This means it does not solve the unwanted copies problem. Instead it solves the problem that windows forgets to respect the excluded folders. – mgutt Apr 15 '16 at 7:36
  • I gave this reference because it was the clearest to follow. I saw other threads where this was offered rather as the solution for the duplicates problem - to restart from scratch. No other solution was ever offered anywhere that I have looked, although this problem seems to be quite frequent. Which is the reason why I suggested a third-party product. – harrymc Apr 15 '16 at 7:47

I had exactly the same problem and I think I know why.

My external drive for backup was FAT32 1.8TB. At times, I received popup messages saying that there was a limitation. And indeed, I had a few files over 4G in size that were NOT backed up (Outlook desktop .pst files).

So I reformated the drive from FAT32 to exFAT. After 4 days, my backup drive was full and I confirmed there were several backup copies of files that had NOT changed.

From what I read, in order to see which files have changed, File History needs the USN Journal (Update Sequence Number Journal) which is part of NTFS, but not exFAT.

But I like File History. I did reformat that external drive from exFAT to NTFS. I notice that most of the files no longer get copied multiple times. Some files that have kept the same size (e.g. outlook .pst) but that have probably changed in content, do get copied again and appear to be duplicates. So I am happy but I will monitor.

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  • This doesn't apply to my case, unfortunately, as my network drive is already NTFS. – Indrek Aug 2 '16 at 9:01
  • In your case, is your source drive NTFS? Here is another thought: Is it possible that another app (or virus) changes the files or opens the files for read/write or changes the time stamp in the journal and makes File History beleive the files have changed? I wish you get this resolved, it's worrysome. – TdP Aug 3 '16 at 19:05
  • Source drive is NTFS as well. Unless File History checks some other date than the one Explorer shows, I don't think anything's changing the files behind my back. – Indrek Aug 3 '16 at 19:14

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