Frequently Asked Questions


How can I find out which installer to download?

  1. open the Run dialog by hitting [Windows]+R
  2. type cmd.exe /K echo %PROCESSOR_ARCHITECTURE% and then click OK
  3. check out the top-left corner of the opened command prompt window
    • If it shows x86 download the i386 installer.
    • If it shows AMD64 download the amd64 installer.
    • If it shows IA64 download the ia64 installer.

Can I up- or downgrade over an existing installation?

Yes. There's no need to remove old files, the installer will take care about everything automatically.

My antivirus software says UltraDefrag is infected by a virus. Is it true?

UltraDefrag is open source software, so it cannot contain malicious stuff by definition. For extra safety, to ensure that the compiled binaries haven't been accidentally infected, we test them all carefully on Only when all files pass most of the virus scanners we make an official release. So, if you see a message saying UltraDefrag is infected by a virus, actually that's nothing but a false positive. We do recommend you to report the case to your antivirus software vendor. As a result your antivirus software will get fixed and you won't see the false positives anymore.

General usage

I need to defragment a large file but have no sufficient free space gap on the disk, what should I do?

To consolidate free space you can try the full optimization. If it fails to achieve the desired result try one of the following:

  • Move all files to another disk, reformat the original disk and move files back. Everything will be perfectly settled in the beginning of the disk.
  • Use GParted or Partition Magic software to shrink the disk. Then expand it back to the original size to get a continuous free space gap at the end.

After defragmentation I see my restore points disappeared, what happens?

The system restore service sometimes tracks file movements. When it exhausts all the disk space reserved for restore points it eliminates elder stuff to release some space for further tracking. Due to this reason we recommend to use backup software instead to keep valuable data backed up.

How to move everything to the beginning of the disk?

Usually it doesn't make sense to move big fragments, but if you'd like to get all files perfectly sorted or just want to pack everything as tight as possible before partition shrinking you can easily do it. Just set the fragment_size_threshold parameter to 0, the optimizer_file_size_threshold parameter to 15 EB and unset all filters. This way UltraDefrag will move all files, regardless of their fragments size, to the beginning of the disk.

I have a volume with no drive letter assigned, how can I defragment it?

Go to Start > Control Panel > Administrative Tools > Computer Management > Storage > Disk Management and assign a drive letter to the volume. Then defragment it and, if you wish, remove the assigned letter afterwards. To automate the process the diskpart utility can be used as shown in the Console Interface chapter of this handbook. The only drawback is that in some cases a reboot may be required to release the assigned drive letter, especially on older systems like Windows XP.

Graphical interface

When will the cluster map become interactive, so I'll be able to know where individual files are located on disk?

When defragmentation algorithms are quite efficient, it's definitely not necessary to know locations of individual files - anyway you'll get your drive optimized quite well. Maybe we'll implement the discussed feature later, but now it's time for more significant improvements.

Why configuration files are better than one settings window with tabs?

Configuration files are easy to edit, even in Windows Notepad.

Why the progress percentage updates irregularly?

The progress percentage measures disk space, not number of files. So it advances pretty quickly when the program deals with big files, and slows down significantly when thousands of small files are in the queue.

Why the progress sometimes exceeds 100% for FAT disks?

On FAT disks space gets immediately released after file movements, so it might happen that more files get fully defragmented than initially calculated.

Why is the disk name not displayed?

Windows Explorer replaces empty disk names by Local Disk or similar, but UltraDefrag doesn't.

Why is only the last report displayed, if I choose to display multiple reports?

Browsers which do not support tabbed browsing are reusing the same window. This is a limitation of the way a web page is opened from within Explorer.

Why are multiple windows opened, if I choose to display multiple reports?

If your browser supports tabbed browsing open one instance of it before you display the reports. This will open each report in a new tab depending on your browser configuration.

When I click Settings > Options the program fails to open the options.lua file, what's going on?

Usually it happens on 64-bit systems when a 32-bit text editior is associated with the .lua file extension. To fix the problem just install a 64-bit edition of the editor or associate the .lua extension with the built-in Windows Notepad.

Boot time interface

Why some files are still fragmented?

Inspect the file fragmentation reports to find out the reason. Some system configurations are locking files even at boot, which can't be prevented. In some cases free space regions aren't big enough to hold the entire file. You might fix that using the quick optimization which consolidates free space a bit.

How can I disable the boot time defragmenter manually?

Remove the defrag_native entry from the following system registry parameter:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\BootExecute


How many differences are between the disk processing algorithms of UltraDefrag and well known MyDefrag (previously JkDefrag)?

Both programs have similar disk analysis algorithms, but defragmentation is done in different ways. While MyDefrag gives more control over files placement, UltraDefrag uses much simpler algorithms which are faster and easier to use.