Free (released under the GNU General Public License) disk defragment and optimize utility for Windows 2000/2003/XP/Vista/X64. Completely automatic and very easy to use, fast, low overhead, with several optimization strategies, and can handle floppies and USB disks/sticks. Included are a Windows version, a commandline version (for scheduling by the task scheduler or for use from administrator scripts), a screensaver version, a DLL library (for use from programming languages), and versions for Windows X64.  Download JkDefrag v3.26 (402kb) for Windows 2000/2003/XP/Vista  Download JkDefrag64 v3.26 (391kb) for Windows X64

Free GNU software

If you are a programmer you might be interested in the sources. Included is a DLL library (released under the GNU Lesser General Public License) containing all the defragger subroutines, which you can call from just about any programming language (for example Delphi and Visual Basic).

 Download JkDefrag v3.26 sources (321kb) for Microsoft Visual C++ 2005

 Jump to JkDefrag forum

JkDefrag.exe

Windows version. This is what most people will use. No installation or configuration necessary, it's ready to run and will automatically process all the mounted, writable, fixed volumes on your computer

JkDefragCmd.exe

Commandline version. Specially designed to be run automatically in the background, or from administrator scripts. See the "running" chapter below for a list of commandline options, and the "Frequently Asked Questions" on how to run it automatically with the Windows Scheduler.

JkDefragScreenSaver.scr + JkDefragScreenSaver.exe

Screen saver version. Move (or copy) these two files to the "system32" folder on your harddisk (usually "c:\Windows\System32\" or "c:\Winnt\System32\"). It will automatically become visible in the list of screensavers as "JkDefrag screensaver" and can be used just like any other screensaver (right-click somewhere on your desktop and select Properties/Personalize, then select the Screen Saver tab).
Note: on Vista the screensaver only works with User Account Control turned off (see Control Panel, User Accounts, Turn User Account Control on or off).
Note: screensavers do not lengthen the lifespan of CRT and LCD monitors, contrary to popular belief. It is better to let the monitor be turned off by the Windows energy saving settings.

• Black: empty
• Dark-green: in use by unknown data
• Light-Green: regular files
• Green: spacehogs
• Yellow: fragmented
• Red: unmovable
• Pink: system files
• White: busy

Snapshot of JkDefrag in action. The program is completely automatic,
there are no buttons and no pull-down menu's.

Permissions

JkDefrag needs "full control" permissions to all files and disks that it must defragment/optimize. On a default Windows system the "administrator" userid has full permissions to all files and disks. Users can also run JkDefrag, but then it can only defragment/optimize the files and disks for which the user has "full control". On Windows Vista: right-click the JkDefrag program and select "run as administrator".

Stopping

All versions of JkDefrag can be stopped safely at any time, there is no risk of losing data or corrupting your disk. You can use all the usual ways to stop a Windows program, such as pressing ALT-F4, clicking the 'x' in the top-right corner, via the pull-down menu in the taskbar, or by killing the program via the task manager or another utility. The commandline program can be stopped the same way, plus by pressing CTRL-C, or BREAK. It may take a bit of time for the program to actually stop, JkDefrag will finish the current file in the background.

Fixup

Defragment, rezone, and reclaim MFT. For more information see the "How it works" chapter.

Fast optimization

This optimization strategy is designed for every day use. It moves a minimum of data on the harddisk and finishes very quickly, but will not fill all the gaps on the disk. The strategy scans for gaps on the disk and fills them with files from above.

Sorted optimization

All the sorting optimizations WILL CREATE FRAGMENTS. This is by design, it is not a bug. For more info see the Frequently Asked Questions.
These sorting optimizations are for incidental use once in a while. They take a lot of running time and data movement because they rewrite all the data on the disk. The strategies vacate a small area on disk and then fill it up again with the files in the selected order.

• Sort by name: very good for fast program starting. The files used by a particular program will be very close together on disk.
• Sort by size: placing all the small files together at the begin of the disk will dramatically reduce the average file seek time.
• Sort by last access: files that have not been accessed in a while are probably unimportant and are best sorted to the back.
• Sort by last change: placing files together that change a lot (for example databases and logfiles) will speed up regular operation of the system.
• Sort by creation time: The oldest files on the disk are likely to be important system files, for example used when Windows is booting.

Note: If you want to sort by last access time then first make sure your virus scanner (and other programs that scan all files on disk) do not change that time.

Force together

Intended for partition resizing. All movable files are moved to the beginning of the disk, even if it means fragmenting them to fill gaps that cannot be filled otherwise.

Move to end of disk

Move all the files to the end of the disk, making more room at the beginning of the disk. Intended for big and rarely used files such as logfiles, backup archives, installation files, and such.

Logfile

JkDefrag writes all messages to a logfile called "JkDefrag.log", or "JkDefragCmd.log", or "JkDefragScreenSaver.log", depending on which version you are using. You can inspect the logfile if you want, it's a flat-text file. The logfile is automatically cleared when the program starts, it does not grow to infinity.

Tip: Cleanup old junk from your harddisk before running JkDefrag.

Tip: Reboot before running JkDefrag. This will release files that are in use, so they can be defragged.

Tip: Stop your realtime virus scanner before running JkDefrag. Virus scanners check all disk activity, making defragmentation and optimization very slow.

Tip: Move the swapfile to another volume, reboot, defragment, and move the swapfile back. If you don't have a second volume then temporarily make the swapfile small, for example 100Mb.

Tip: If an application (for example a database) prevents certain files from being defragged then stop the application, run JkDefrag for the particular data directory only, and restart the application.

How safe is it?

JkDefrag is based on the standard defragmentation API by Microsoft, a system library that is included in Windows 2000, 2003, XP, and Vista. Most defragmenters are based on this API, including commercial defragmenters. JkDefrag is therefore very solid and there is no risk of losing data. You can stop the program at any time, it will finish the current file in the background. If your disks use NTFS then you're even safe when the computer crashes in the middle of defragging. Nevertheless, it's still a good idea to backup before defragmenting, just like with other defragmenters, because the heavy use of the harddisk may trigger a hardware fault.

Defragmentation and optimizing will not only make a harddisk faster, but also lengthen it's lifespan. The disk will have less work to do and therefore have less wear and tear. Secondly, the sorting optimization strategies (see the "-a" option) will refresh all the magnetic data on your harddisk. However, defragmenting and optimizing is work, so excessive defragmenting and optimizing can actually cause more wear and tear than it prevents. JkDefrag is therefore set for "fast" optimization by default, intended to be used on a daily basis. The other optimizations should only be used occasionally.

How do I specify an option, or select a single disk (or folder or file)?

Take a look at the GUI wrappers, see the "Contributed by other people" chapter. Personally I find the commandline the easiest way to specify options. Another way is to create a shortcut to "JkDefrag.exe", open the properties of the shortcut, and add the desired commandline options (for example "-a 7") or the name(s) of the disk/folder/file (for example "C:") to the end of the "target" line. For example:

"C:\JkDefrag\JkDefrag.exe" -a 7

"C:\JkDefrag\JkDefrag.exe" D:

Tip: In the same properties window you can select "minimized".
Tip: See the "-q" option to exit automatically when finished.

Where is the Stop button?

All versions of JkDefrag can be stopped safely at any time, there is no risk of losing data or corrupting your disk. You can use all the usual ways to stop a Windows program, such as pressing ALT-F4, clicking the 'x' in the top-right corner, via the pull-down menu in the taskbar, or by killing the program via the task manager or another utility. The commandline program can be stopped the same way, plus by pressing CTRL-C, or BREAK. It may take a bit of time for the program to actually stop, JkDefrag will finish the current file in the background.

How can I run JkDefrag automatically every day?

It's a great idea to run JkDefrag automatically every day by adding it to the Windows scheduler, like this:

• Start -> Control Panel -> Scheduled Tasks -> Add Scheduled Task
• The wizard starts, click 'Next'.
• Use the 'browse' button to select the 'JkDefragCmd.exe' program.
• Select 'daily', next, select a time, next.
• Enter a userid/password with administrator privileges, click 'Finish'.

Tip: see the "Settings" of the scheduled task to run only when the computer is idle.

How do I use the screensaver?

See the instructions in the "Install" chapter.

How to run JkDefrag at boot-time?

It's very easy to run JkDefrag automatically in the background when the computer starts via the Windows Task Scheduler:

• Start -> Control Panel -> Scheduled Tasks -> Add Scheduled Task
• The wizard starts, click 'Next'.
• Use the 'browse' button to select the 'JkDefragCmd.exe' program.
• Select 'When my computer starts', click next.
• Enter a userid/password with administrator privileges, click 'Finish'.

Note: This will not defrag system files such as the pagefile. To do that see the "see also" chapter for a link to Pagedefrag, a free utility by Microsoft Technet (formerly SysInternals).

How to start minimized, or maximized?

Make a shortcut to the "JkDefrag.exe" program, open the properties of the shortcut, find the "run" setting, and select "minimized" or "maximized".

How much minimum free disk space does JkDefrag require?

JkDefrag does not require a minimum free disk space, unlike many other defraggers. But:

• Windows reserves a certain percentage of the disk for expansion of the MFT. This space is counted by Windows as free space because it can/will be used for regular files when the rest of the disk is full. But JkDefrag cannot use this free space.
• A file can only be defragmented if there is a gap on disk big enough to hold the entire file. There may be plenty of free space, but what is needed is a single big gap. In these cases JkDefrag will try to reduce the number of fragments in the file by using the biggest gaps available.

Why is my disk not perfectly optimized?

• There are many files that cannot be moved while Windows is running, because they are in use by an application, or by a service, or by Windows itself. See the "-d" commandline options and the logfile for more information. They can be anywhere on disk and are usually fragmented into microscopically small segments. In other words, the harddisk is not a big block of space where files can be moved at will, but thousands of little blocks bounded by unmovable data.
  A typical harddisk can easily contain tens of thousands of files, all with different sizes. What is the optimum way to organize the files into the blocks? The number of permutations is astronomical, it boggles the mind. JkDefrag doesn't even try to calculate them all. It concerns itself with only one block at a time, trying to fit only files from above the block, and limits itself to 0.5 seconds of calculating time.
  So it's very unlikely, if not impossible, for JkDefrag to perfectly optimize your disk, more's the pity.
• Gaps are only filled with files from above the gap (fast optimization). If there are no files that fit the gap (all files are bigger) then the gap cannot be filled.
• Files can only be fully defragged if there is a gap large enough to hold the entire file. If no such gap is available then JkDefrag will try to reduce the number of fragments by moving the file to the largest gaps available.
• JkDefrag maintains a "free space" area between the directories and the regular files, and between the regular files and the space hogs. This is by design. See the "-f" commandline option to control the size of these free spaces.

Why do the sorting optimizations create fragments?

The sorting optimizations will move all the data to the beginning of the harddisk. But there may be some unmovable files in the way. Instead of leaving gaps (if a file doesn't fit between the last file and the unmovable file), the program will "wrap around" the unmovable files by splitting regular files into fragments. This may seem strange for a defragmenter, but the fragments are aligned and therefore have a very small impact on performance. Gaps however would make all the files above the gaps slower, because they would then be placed at a slightly slower part of the harddisk than they need to be. The fragments look terrible on the screen and in the statistics, but are there to make your harddisk faster!

What are SpaceHogs?

SpaceHogs are less important files that take up a lot of space. JkDefrag moves them behind the directories and the regular files, to make those faster. The internal list of SpaceHogs is (you can add more with the "-u" commandline option):

• Files bigger than 50 megabytes
• Files not accessed in the last month
• ?:\Program Files\Installshield Installation Information\*
• ?:\Archivos de programa\Installshield Installation Information\*
• ?:\Arquivos de programas\Installshield Installation Information\*
• ?:\Ohjelmatiedostot\Installshield Installation Information\*
• ?:\Program\Installshield Installation Information\*
• ?:\Programas\Installshield Installation Information\*
• ?:\ProgramFiler\Installshield Installation Information\*
• ?:\Programme\Installshield Installation Information\*
• ?:\Programmer\Installshield Installation Information\*
• ?:\Programmes\Installshield Installation Information\*
• ?:\Programmi\Installshield Installation Information\*
• ?:\RECYCLER\*
• ?:\RECYCLED\*
• ?:\$RECYCLE.BIN\*
• ?:\System Volume Information\*
• ?:\WINDOWS\$*
• ?:\WINDOWS\I386\*
• ?:\WINDOWS\ie7updates\*
• ?:\WINDOWS\Installer\*
• ?:\WINDOWS\ServicePackFiles\*
• ?:\WINDOWS\SoftwareDistribution\*
• ?:\WINDOWS\Downloaded Installations\*
• ?:\WINDOWS\Ehome\*
• ?:\WINDOWS\Fonts\*
• ?:\WINDOWS\Help\*
• ?:\WINDOWS\IME\*
• ?:\WINDOWS\Speech\*
• ?:\WINDOWS\Symbols\*
• ?:\WINDOWS\system32\dllcache\*
• ?:\WINNT\$*
• ?:\WINNT\I386\*
• ?:\WINNT\ie7updates\*
• ?:\WINNT\Installer\*
• ?:\WINNT\ServicePackFiles\*
• ?:\WINNT\SoftwareDistribution\*
• ?:\WINNT\Downloaded Installations\*
• ?:\I386\*
• *.7z
• *.arj
• *.avi
• *.bak
• *.bup
• *.bz2
• *.cab
• *.chm
• *.gz
• *.ifo
• *.log
• *.lzh
• *.mp3
• *.msi
• *.old
• *.pdf
• *.rar
• *.rpm
• *.tar
• *.vob
• *.z
• *.zip

Note: Some virus scanners and other programs that scan all files on disk, will change the last access time of all items on every run, effectively disabling that particular SpaceHogs criterium. The other criteria still apply, though.

Can I run JkDefrag outside Windows?

JkDefrag is based on the Windows defragmentation library, so Windows must be started. JkDefrag can be run from a bootable Windows CD-rom (such as BartPE, see http://www.bootcd.us/), but cannot be run from a DOS bootable floppy.

Can JkDefrag do continuous background defragging?

In my opinion continuous background defragging and optimization is marketing hype and a bad idea. There is considerable overhead (CPU, memory, disk) that may actually make your computer slower instead of faster, and it will wear out and shorten the lifespan of your harddisk. I advise defragging once a day (via the Windows Task Scheduler) at the most.

Can I "hide" the program from users?

Create a special userid (for example "jkdefrag") with administrator permissions, then add a schedule to the Windows Task Scheduler (see above) and specify that userid when asked for. The task will then run on that userid and not show anything on the user's screen. But I advise against it, I think it will needlessly worry the user when he sees a lot of mysterious disk activity.

How do I disable Vista's build-in defragger?

1. Open the Windows Control Panel
2. In the left menu select "Control Panel Home"
3. Click "System and Maintenance"
4. Under the "Administrative Tools" section at the bottom, click "Defragment your hard drive"
5. You may need to grant permission to open the disk fragmenter
6. Click or unclick "Run on a schedule (recommended)" depending if you want this feature enabled or disabled.
7. Click OK

How do I defragment "C:\hiberfil.sys"?

This huge file is used by the hibernation facility and cannot be defragged on a running system. But there is a trick:

Windows Vista:

1. Click Start -> All Programs -> Accessories, right click on "Command Prompt", and then click "Run as Administrator". If User Account Control (UAC) asks you for permission, permit the Command Prompt to run.
2. Enter "powercfg -h off" (without the quotes).
3. Reboot. The "hiberfil.sys" file will be automatically deleted.
4. Repeat point 1
5. Enter "powercfg -h on" (without the quotes).
6. Reboot.

Windows XP:

1. Open the Windows Control Panel
2. Double-click Power Options
3. Click the Hibernate tab, de-select the 'Enable hibernate support' check box, and then click Apply.
4. Reboot. The "hiberfil.sys" file will be automatically deleted.
5. Go to the Windows Help & Support Center and search for 'enable hibernation'. It should be the first result. The instructions detail some other steps you may need to follow to reactivate the hibernation.

Why use this defragger instead of the standard Windows defragger?

• Much faster.
• Totally automatic, extremely easy to use.
• Optimized for daily use.
• Data optimization, several strategies.
• Directories are moved to the beginning of the disk.
• Reclaims MFT reserved space after disk-full.
• Maintains free spaces for temporary files.
• Can defrag very full harddisks.
• Can defrag very large files.
• Can defrag individual directories and files.
• Can be run automatically with the Windows Scheduler.
• Can be used from the commandline.
• Can be used as a screen saver.
• Sources available, can be customized.

Why use this defragger instead of a commercial or shareware defragger?

• It's free.
• Totally automatic, extremely easy to use.
• Optimized for daily use.
• Several optimization strategies.
• Directories are moved to the beginning of the disk.
• Reclaims MFT reserved space after disk-full.
• Maintains free spaces for temporary files.
• Can defrag individual directories and files.
• Can be used from the commandline.
• Can be used as a screen saver.
• Sources available, guaranteed to be free of spyware, malware, nagware, and such.

Tip: The first partition on a harddisk is significantly faster than other partitions. Try to use other partitions only for "SpaceHog" data (see above "What are SpaceHogs?").

Phase 1: Analyze

JkDefrag has to scan all the files on the disk to determine if they are fragmented and where they are.

Phase 2: Fixup

JkDefrag walks through all the files on the harddisk and does the following:

• All fragmented files are defragmented, simply by moving them to the first gap on the disk that is big enough. If there is no gap big enough then the defragmenter will reduce the number of fragments in the file by moving as much of the file as possible into the largest gaps available.
• Windows reserves a percentage of the disk for the MFT (Master File Table), but can place normal files there if the rest of the disk is full. The files will remain there, even when there is enough space again. JkDefrag looks for files in the MFT reserved space and moves them to normal diskspace, making the reserved space available again for the MFT.
• Regular files are moved out of the directory zone, and spacehogs are moved out of the directory and regular zones. This prepares the disk for the next step (optimization) so it can do a better job. See below for more information about the zones.

Phase 3: Optimize

• On most harddisks the beginning of the harddisk is considerably faster than the end, sometimes by as much as 200 percent! See the link to "HD Tune" in the "See Also" chapter for a nice little free program to measure your disk. The default JkDefrag optimization strategy therefore moves all files to the beginning of the volume. It is intended for daily use and will simply fill gaps with files from above, very quick and with very little data movement.
• Sorting the files on your disk can give you even more speed. There are several sorting strategies to choose from (see the "-a" options). These are all very slow and intended for occasional use only.
• JkDefrag classifies files into 3 zones: directories (zone 1), regular files (zone 2), and space hogs (zone 3). Files outside their zone are moved to their zone. Directories are perhaps the most accessed data on disk, so zone 1 is placed at the beginning of the harddisk. After the directories comes a free area (see below), then zone 2 with regular files, another free area, and then zone 3 with space hogs, which are files bigger than 50 megabytes; files not accessed in the last month; files with certain filenames such as archives; files in the recycle bin; service pack files, and other infrequently accessed data. The begin and end of the zones is determined automatically, see the "-f" option.
• A running computer will create and delete temporary files like there is no tomorrow. If the harddisk were completely optimized then the only place for new temporary files would be behind all the other data. Which is rather slow. So JkDefrag maintains a free space of 1% of the total disk space between zone 1 (directories) and zone 2 (regular files), and between zone 2 and zone 3 (space hogs).

• The "-a 9" sorting method (and possible the other sorting optimizations) can sometimes get into an infinite loop.
• The "Prefetch\Layout.ini" file is not yet supported. This means that JkDefrag will undo the boot optimization of the build-in XP and Vista defragger.
• The Microsoft defragmentation API on Vista can defragment and move the MFT, but JkDefrag cannot use this capability yet.
• The Windows defragmentation API refuses to move directories on FAT32 filesystems. This is a known FAT32 limitation and not a bug in JkDefrag.
• The Windows defragmentation API on Windows 2000 does not work on disks that were formatted with a clustersize greater than 4KB. This is a known API limitation and not a bug in JkDefrag. There is no risk of losing data, the API simply refuses to move files.
• A user has reported that his computer freezes when Avira Antivir Professional starts while the JkDefrag screensaver is active.
• A user has sent me a message that HP advises against defragmentation of the special "recovery" partition on their computers. My defragger uses the standard Microsoft defragmentation API, so I think it is safe to use, but I don't know for sure. I have not found any additional information about this issue anywhere on the internet.
• JkDefrag makes a special exception for files used by SafeBoot, Acronis OS Selector, and DriveCrypt. The files will never be moved. If you know of any other software that needs a special exception then please let me know.

 French version

JkDefrag and all the docs translated into French by Sparad0x. Included are a Setup program and the sources.

 German version

JkDefrag and all the docs translated into German by Markus Hörl. Also available is a Setup program and a GUI wrapper.

 Spanish version

JkDefrag and all the docs translated into Spanish by Manuel Montero. Also available is a translated version of Emiel Wieldraaijer's GUI.

 Italian version

All the docs (not the program itself) translated into Italian by Danilo Angaroni.

 Traditional Chinese version

JkDefrag (the program, not the docs) translated into Traditional Chinese by Eddy Guo. Also available is a GUI. Sources included.

 JkDefragGui

GUI program by Emiel Wieldraaijer. In English, Dutch, German, French, Spanish, Portuguese, Italian, Romanian, Swedish, Mayar, Polish, Bulgarian, Catalan, Japanese, Slovenian, Russian, and Greek/Hellenic. Includes the "autoit" sources.

 JkDefragGui

GUI program by Dirk Paehl. In English. Sources are included.

 JkDefragTWGUI

GUI program by Thorsten Willert. Can handle multiple "jobs". In English, although the homepage is in German.

 JkDefragStarter

GUI program in German by Thomas Kolb. C++ sources are included.

 JkDefrag forum

I have set up a forum for JkDefrag, a place where you can ask questions, give feedback about features you would like, share your experiences, share code that uses the defragger library, and other things about JkDefrag.

 HD Tune

Measure your harddisk and discover how much faster it is at the begin than at the end. Can also monitor the temperature of your harddisk and scan for surface errors.

 Defragmentation

Wikipedia page about defragmentation.

 Pagedefrag by Microsoft TechNet (formerly Sysinternals)

Paging files and registry hives cannot be defragmented on a running system. This sweet little utility will automatically defragment those files when the system is booting. The counterpart of this utility is "Contig", a small defragger for use on a running system, but my defragger is far superior.

 DiskView by Microsoft TechNet (formerly Sysinternals)

Small utility that shows which file is using a particular location on the harddisk. Use this if you are wondering which file JkDefrag could not move. The utility takes a while to start up, because it has to analyze all files one by one, but it's a very nice little utility nevertheless.

 HDview

Similar utility as DiskView, by Alexander Freudenberg. Much faster and for NTFS only.

 ScanDefrag

A very nice utility that will run maintenance programs as early as possible in the Windows startup. My defragger is one of the supported programs, others are for example Microsoft's Disk Cleanup, ScanDisk/Chkdsk, Norton's Disk Doctor, and others.

 AutoRuns by Microsoft TechNet (formerly Sysinternals)

Handy utility to discover all the things that are started when windows is booting.