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Best disk defragmenter tools 2021

Best disk defragmenter tools 2021
(Image credit: Defraggler)

Defragmenting, and therefore using the best defragmenter software, is a tricky one. It used to be a dreadfully slow process that you’d only attempt if something had gone dreadfully wrong with your hard drive, and even on the smallest drives you’d need to leave it overnight. As drives have got bigger, computers have got faster, and operating systems have become more sophisticated, it has become something that runs in the background while you’re using your PC, but even this can require a helping hand from time to time, whether it’s an internal or external hard drive.

Fragmentation is something that happens to data on a hard drive that’s regularly used. When the drive is new, data can be written sequentially. But once you’ve deleted a bit, your computer will try to use up that freshly vacated space before it writes to untouched areas of the disc. If the new data is larger than the hole left by the deletion, it will write part of it there and part in the next bit of free space, leaving a note as to where the rest of the data is - this way, your drive becomes fragmented.

Defragmentation, or defragging, is the art of piecing all the data together so it lays in nice even strips without your hard drive’s seeker head having to zip all over the drive platters searching for the next bit. It’s a problem that only applies to spinning hard drives - SSDs are fast enough that they can pull your data out wherever it’s written, and defragging an SSD, although possible, only adds to the problem of premature wear.

While it’s not the same as the best repair software for your PC, if your main hard drive is of the old-fashioned mechanical variety, then a good defrag every now and then can really help its performance, over and above that the operating system does for you.  


1. O&O Defrag: Best disk defragmenter tool overall

o&o smart defrag: Best disk defragmenter overall

(Image credit: o&o smart defrag)

O&O Defrag

If you want loads of features and a clean design, you can't beat O&O Defrag

Huge range of features
Updated hard disk and SSD algorithms
Straightforward design
A little expensive

The powerful algorithms, broad range of hard disk and SSD features and the sensible, straightforward interface make O&O Defrag the top choice. O&O’s Defrag application has been one of the most popular defrag tools for years now, and it’s no wonder – this utility is easy to use and packed with powerful settings.

The latest iteration, version 24, includes new features that make the optimization process smoother and more powerful. The underlying defrag engine has been reconfigured to support new features in Windows 10, and a new installation method picks the best settings for your PC – so you can install and start using the app without any extra configuration. There are updated methods for optimizing and extending the lifespan of SSDs too, which is important – many of us use SSDs, but many apps are still based around hard disks.

These new features are bolstered by powerful, familiar functionality. The core defrag algorithm is market-leading and has been made faster in this release, and the app has a disk cleaning tool to remove temporary and unnecessary files. It’s got automatic background and scheduled functionality, filters so you can easily find your most fragmented files, and you can access lifetime statistics so you can see exactly what space and time you’ve gained.

The app is straightforward, with clear options, quick defrag features and graphics that show you the state of your drives. Extra features can inspect individual file clusters, determine file positions and throttle system resources so you can still use your PC while the app works. You can even optimize the files required when your PC boots.

This app’s only real weakness is its lack of a free edition, but the Professional, Workstation and Server versions are affordable, with prices that range from $30 to $200 – and those latter apps give additional features for administrators who want to keep a network of PCs in top condition which go a long way to justifying the higher prices.


2. Defraggler: Best for overall PC health

Defraggler: Best disk defragmenter for overall PC health

(Image credit: Defraggler)

Defraggler

This one will give your whole PC a decent health-check

Slick hard disk and SSD options
Supports scheduling
Includes benchmarking
Pro version is expensive

Defraggler’s free version is an effective tool for defragging hard drives without weighing down your system, but we’d recommend that app bundle – you get more features alongside extra tools that can manage your entire system.

Defraggler is made by a company called Piriform, and that firm is one of the most experienced when it comes to PC optimization and management – it also produces CCleaner, Recuva and Speccy, which are well-known tools for looking after your system.

Piriform’s defrag tool has a free version, which serves up all of the key options for keeping your hard disk in shape – and it can use its algorithms to keep your SSDs organised, too. It works with external drives as well as internal disks, and you can defragment specific drives and folders. It has a benchmark tool to evaluate your performance improvements, and you can analyze drives to determine whether or not you need to run any defrag processes. Scheduling is supported, but the app can’t start defragmentations when your system is idle.

Defraggler serves up straightforward charts to illustrate what’s going on with your drives. Upgrading to Piriform’s Professional edition costs a hefty $25 and nets you better support and automatic updating, and spending an affordable $30 will get you Piriform’s entire family of apps – Defraggler Professional will be included alongside CCleaner, Speccy and Recuva’s professional versions. That’s a far better deal.


3. IOBit Smart Defrag 6: Best defrag for gamers

iobit smart defrag: Best disk defragmenter for gamers

(Image credit: iobit smart defrag)

IOBit Smart Defrag 6

If you're running a gaming rig and need an HDD clean, this is for you

Game-specific options
Loads of features elsewhere
Pro version is cheap
Ads included in free version
Tries to install extra software

IOBit’s Smart Defrag lives up to its name, with options that allow for a huge amount of customization on an app-specific basis – handy if you’re a gamer or professional user who wants to keep certain software running at peak performance. It’s even got a Game Optimize mode that can be used to deliver a smoother and faster gaming experience.

Beyond that, Smart Defrag has an impressive slate of options – you can defrag entire drives, specific files and folders or specific apps, or defrag your system files when you boot the PC, so the computer has been optimised before you start work. Smart Defrag works with hard disks and SSDs, and it supports scheduled scans.

Handily, Smart Defrag has a free version, but be aware that you’ll have to skip past some extra apps during the installation process and deal with ads when you boot the software. This app also can’t perform defrags when your system is idling. The Pro version costs a reasonable $12 and includes new features, like disk health monitoring and specific large file defrags. This is a good defrag app, and it’s a great option for gamers.


4. Puran Defrag: Easiest to use

Puran Defrag: Best disk defragmenter for ease of use

(Image credit: Puran Defrag)

Puran Defrag

If you need easy, rather than feature-filled, then Puran is a perfect fit

Effective, usable interface
Registry and scheduling tools
Utilities suite available
No portable option
More features available elsewhere

Puran Defrag is the best option if you’re not a particularly advanced PC user but if you still want an app that can keep your hard disks and SSDs in top condition.

This free tool has an impressively slick and simple interface that makes it easy to get started. Booting the tool loads up a clear list of your drives, a map of their storage setup and obvious options to analyze and defrag the disks. There are options to make the task low-priority to stop it impacting on your system’s performance, to shut down the PC after the defrag has completed and to customize the boot, defrag and disk-checking process.

There are more options if you delve into Puran’s extra tabs. There are detailed scheduling options, Registry defragmentation tools, an intelligent optimizer to increase system speed and options to exclude specific files or files at certain sizes from operations. Sadly, the app doesn’t have a portable version and can’t manually run free space defrags. And, while it’s easy to use, other apps do have more features and slicker interfaces – and offer more detail when it comes to seeing exactly what’s been defragged.

Puran Defrag’s free version is an effective tool if you don’t want something too complicated, and you can also download Puran’s free Utilities suite, which also serves up tools for disk cleaning, file recovery, gaming, disk wiping and much more.


5. Auslogics Disk Defrag: Best disk defragmenter for pro-PC users

Auslogics defragmenter: Best disk defragmenter for pro PC users

(Image credit: Auslogics defragmenter)

Auslogics Disk Defrag

If you're a pro-PC user this software will give you more control

Very fast operation
Broad range of options
Works with SSDs
Potentially confusing interface
Some features missing in free version

This app places a huge emphasis on getting your defrag operations completed quickly – Auslogics boasts that it usually takes less than ten minutes to complete operations on a standard hard disk.

This tool is ideal for those in a hurry, then, and it has a good slate of features elsewhere. It has specific routines for different kinds of drives, it can remove temporary and unneeded system files, and its operations can be scheduled and set to run when your system is idle.

Elsewhere, Auslogics can exclude files and folders from defrag runs, run analyses and quick defrag operations, provide reports on your PC’s status and even just defrag the files and applications that you use most often. There are more options deep within the app, including settings to change how the charts look, use different features for SSDs and move system files around on your hard disk – to improve boot times.

The free version is packed with features, and there aren’t many downsides – the only issue is that the interface and the broad selection of options may be confusing for less knowledgeable users. If you spend $25 on the Pro version you get loads more, including specific SSD algorithms, better disk cleanup options and free space wiping alongside better scheduling options and a license for use on three different PCs.

There are free applications out there that have more options, but Auslogics’ Pro version is packed with versatility, and the free and paid versions are both extremely fast. This is the ideal defrag tool if you have a need for speed.


6. Glarysoft Disk SpeedUp: Best free option

Glarysoft disk speedup: Best disk defragmenter for free

(Image credit: Glarysoft disk speedup)

Glarysoft Disk SpeedUp

If you'd rather pay nothing, and put up with fewer features, Glarysoft has you covered

Primarily a free tool
Good core functionality
Automatic and scheduled defrags supported
Misses some advanced features
Doesn’t work on removable drives

For most of us, though, Glarysoft’s free version will be more than adequate thanks to its effective design and decent functionality. It’s our top choice if you just want a free defrag tool.

Glarysoft Disk SpeedUp is the best option if you want a free, unfussy and effective defrag tool. Booting the software loads up a clear picture of your drive health and clear options for improving it – pick a drive and you can run analysis, defrag the drive, optimize the storage and choose to turn your PC off after the operations are complete.

Glarysoft’s app supports individual file and folder defrag operations, and you can run operations with different levels of priority – so you can speed things up if you want the defrags to finish quickly or slow them down if you’d like to keep working while the app does its thing. This tool can automatically start defrag processes if your system is idle, and you can choose how long it needs to be idle for before processes begin, and basic scheduling is also supported.

The fact that Disk SpeedUp is free means that some functionality is missing. It doesn’t work on removeable drives, it doesn’t integrate into Windows Explorer and it doesn’t have a duplicate file finder, and other apps offer more customization and faster operations. It does have a small advert in the corner, too, but it’s far less intrusive here than on other free tools.

Happily, though, this app has ample functionality for most mainstream defrag operations. It also forms part of Glary Utilities, which is a suite of more than twenty tools for PC optimization. A Pro version is available for $20, and it includes free technical support, commercial usage rights and enhanced optimization features – including for Disk SpeedUp.


What is defragmentation?

Put simply, defragmentation is the removal of fragmentation from a computer hard disk. That then poses another question: what is fragmentation? The files on your hard drive aren’t always stored in continuous blocks, operating systems sometimes have to stop writing a file halfway through because they encounter data they can’t delete, and have to finish writing the file elsewhere on the disk, leaving behind a little forwarding address for the rest of the data. 

What this means when your PC comes to read the file back is that it takes longer than it should, as the drive head reads half the file, then follows the forwarding address to where the rest is located before finishing its read. Defragmentation restores the files to continuous blocks, so the drive head can read them in one go and doesn’t have to go hunting around in the rest of the disk.

You’ll note from all this talk of drive heads that we’re talking about spinning mechanical hard drives here, and not the newer SSDs. Solid State Drives and Flash drives are much faster, and don’t store their data in the same way as a spinning hard drive, so fragmentation isn’t a problem and defragmenting one would only contribute to them wearing out.

You can defrag external drives if you want to, especially if they’re frequently used, as it may improve performance, but the way those drives are written to - long sequences of writes for stored data, with fewer reads and rewrites - means they’re less likely to suffer from fragmentation. External hard drives are also slow when compared to their internally connected cousins, so you’re less likely to notice a drop in performance due to fragmentation. It’s much more useful if you’ve got an internal hard drive that houses an operating system, or some other data that requires lots of little writes and rewrites while the computer is active.

How does defragmentation software work?

Once you begin a defrag, there’s an analysis phase while the software works out the location of every piece of data on the disk, which data it should be stored next to, and which bits are fragmented. It may produce a map of your drive showing you the types of data. 

Once you ask it to defrag, it can be quite a long process, as it’s an intensive operation that cannot be carried out on a drive with no free space. This is because the software copies the fragmented data from the places it is stored into the free space, where it reassembles it. Then it moves data around on the drive until there is a block of free space available that can hold the data. It then copies the data into this block, and deletes it from the temporary holding space. If your drive is heavily fragmented, this can take a very long time. You’ll know if it's been successful because the defrag software will tell you, and you’ll be able to see from the data map that your files are now held in continuous blocks rather than being scattered across the disk.

Many modern operating systems, such as Windows 10/11 and MacOS, defrag in the background if they think it’s necessary, sorting out fragmentation the moment it appears rather than letting it build up. Modern file systems - the rules computers use to organize their writes to the disk - are also designed to avoid fragmentation. 

You can open a built-in defragging app in Windows from the Start Menu, it’s called Optimize Drives, and this will scan your hard drives and tell you the percentage of fragmentation the data is suffering from. It recognizes the difference between hard drives and SSDs, and allows you to TRIM your SSDs - a sister process to defragmentation that empties all the space once taken up by deleted data and gets it ready for reuse. This again improves performance, as otherwise it would need to be done just before new data was written.

External and Portable storage defragging

In addition to ensuring your Windows machine is regularly defragged and running optimally, we also recommend defragging your external hard disk drives (HDDs). Because these drives don’t typically stay connected to your computer like the one built into your machine, they’re less likely to receive regular maintenance. If you use your external HDD frequently for saving and accessing programs and data, this is especially important to maintain.

In contrast, you do not need to run defragging software on a flash drive (also known as a jump, USB or thumb drive) or on an external SSD. These types of drives are physically different from traditional hard disk drives and don’t have to be defragmented; in fact, the process is usually damaging to them, potentially resulting in a loss of data or a ruined device.

On a side note, you can save your disk defragmenter software onto an external drive. You don’t have to save it onto the specific drive you wish to run it on. Keeping your software stored externally can be convenient in case your computer crashes, or in case you travel frequently and want to run the software on multiple computers. If the latter is true, you’ll want to make sure the software has enough licenses when you initially purchase it to be compatible.

Auslogics defragmenter

(Image credit: Auslogics defragmenter)

Why you don't need to defrag Macs

When you search online for disk defrag software, you’ll see a million returns for defragging a Windows machine and few, if any, for a Mac. You may be curious why this is, but the answer is fairly simple: the file system within a Mac hard disk drive (HDD) is designed differently from one on a Windows computer. Macs actually defrag themselves automatically with built-in utilities, especially if it’s a newer version of the Mac operating system (anything after 10.2). New Mac OS versions automatically check for fragmentation every time you access a file or program.

The only point at which you should be considering defragging a standard hard disk drive on your Mac computer is when less than 10% of storage space is available. When your HDD is this full, Mac OS is commonly unable to run its usual defragmentation program automatically. However, we recommend periodically going through your hard drive to delete old or unwanted files and programs to keep as much space available as possible, or to purchase a larger HDD that better suits your storage needs.

And as we’ve stated elsewhere in this article, you should never run disk defragmenter software on a solid-state drive (SSD). These drives are built differently and don’t fragment – plus, they are designed only to handle a limited quantity of writes and defrag software can lead to SSD damage or failure.

Freeware vs. Paid defrag software: which is best?

While defragmenting is a free service built into Windows 10/11 and MacOS, there are paid-for alternatives from third party developers on offer. These generally replicate a lot of the native functions, but add more of their own, particularly in the form of SSD optimisation tools that go beyond TRIMming. 

Whether you need them or not, will depend entirely on individual use cases. Most hard drives and SSDs left to the operating system’s automatic maintenance routines need no more intervention than that - SSDs are fast enough even when running garbage collection routines, and a hard drive that’s a few percent fragmented is not going to suddenly grind to a halt because of it. Keeping a little free space on your drives - around 10% or so - is important as it enables defragging routines to operate. Macs in particular have a habit of not defragging properly if the drive is too full. Pick up one of the best external hard drives and offload some documents if your drive is more than 80% full.

There are also free third party options available, but we generally advise people to stay away from these unless they’re committed to open-source software. This is because, along with the software you want, you often also download adware, unwanted browser plugins, free trials for programs you don’t want, and more besides. This not only clogs up your system, but acts as a security risk, as many of the programs’ are designed to serve advertising to your PC. Others may demand your credit card details even though they’re meant to be free, or otherwise behave badly. They’re just not worth the hassle, especially as you have a free defragger right there.

iobit smart defrag

(Image credit: iobit smart defrag)

What to consider with disk defragmenter software

Ease of use
What you really want is a program you can set going, and which runs in the background, not bothering you until it announces it has finished. Some have different options for you to set, but we discovered that all of the apps on test provide comparable results if left on their default settings. Another useful feature is the display of statistics and detailed information about your drives, if you're interested in what’s going on in there.

Scheduling
Being able to defrag outside of your work hours is important if you depend on squeezing every FLOP of power out of your rig. There is a performance penalty, both in terms of processor availability and disk bandwidth, but many users will never notice it.

Other scans
Alongside defragmentation, programs may offer registry or driver scans. These are fine, but you need to know what you’re doing. Leaving them on ‘auto’ can lead to the removal or editing of something that your PC relies on to boot up, or use a critical piece of hardware. If everything is working properly, it’s often better just to leave it alone. A few registry entries hanging around from a piece of software you uninstalled are not going to harm your system, but blundering around in there when you don’t really know what you’re doing certainly can. The same goes for drivers, especially since Microsoft has moved to a new driver architecture that isolates them from the rest of the system. A bad driver can no longer lead to the blue screen of death in Windows (particularly as we move to Windows 11) and having some for hardware you no longer use isn’t a problem. They don’t take up much space. One thing driver scans are useful for, however, is identifying which drivers have updates available.

Verification
If you spend money on defragmentation software and wait while it works, having some sort of visual feedback about what it’s doing is nice, and being able to verify that everything has worked properly, and that your drive is now in tip-top condition, is even better. Almost all defrag programs provide a visual map of your drive, but if you’re using a third-party program you can open the Windows app once it’s finished and let it analyze your newly defragmented disk to verify that everything has gone to plan. If the defrag didn’t work, you should still see fragmentation, with files and parts of files spread across the disk.

Alternatively, if you frequently write files to the drive, you might see a small increase in speed from it once it’s neatly organized. The act of writing and overwriting files, however, is what sets the fragmentation process in motion, so you’re in a constant cycle of checking and defragging.

Manual vs. Scheduled

You have full control over when your disk defragmenter program runs – you can put it on a schedule or use it manually whenever you need. Both options have pros and cons, and learning the benefits and downsides to each can help you use the software the most effective and efficient way for your situation.

When you set up a schedule for the software to run, you don’t have to stress over slow performance creeping up every few months or wonder why files are taking longer to access or run. Instead, you can rest assured that your hard drive is optimized. It’s a good idea to schedule your disk defrag software to run if you want to keep your computer healthy but aren’t very tech-savvy. Most of the programs we reviewed are easy enough to use, with clearly labeled buttons. Some even have guides that walk you through the entire process.

If you are an advanced user familiar with the ins and outs of this type of software, you are better off running the program manually. That way, you don’t have to worry about the software running scans and repairs it may not need. When you run it manually, you also have more granular control over the process, and you can run it on additional external hard drives if you want.

What is Boot Time Defrag?

Boot time defrag is typically only used by advanced users who are extremely knowledgeable about computers. By definition, boot time is the time between when you hit the power button and when your computer is ready to use. During this time, your computer starts executing instructions such as loading its operating system and connecting with peripherals like the mouse and keyboard. In a matter of moments, your desktop computer – or laptop or smartphone – is ready to use. On old computers, this process took several minutes, but with newer computers, it only takes a few moments.

Some people say that using defragging software during your computer’s boot time doesn’t make a measurable improvement in performance and isn’t worth the effort. But the general thought behind running boot time software is that since those files are used often (every time you boot up your computer), they surely must experience fragmentation, and by defragging them, you can make the process faster by a few milliseconds.

If you don’t want to mess with these files or deal with the risks of doing so, there are other things you can do to speed up your computer’s boot time. The best thing you can do is to disable programs that launch at startup. Yes, it’s convenient to have all your favorite programs open every time you turn your computer on, but it takes a toll on the machine, and it’s not too difficult to open them manually as you need them. You can also set them to open automatically but at a delayed rate. In addition, you can delete desktop shortcuts, delete old files and programs, install antivirus software, and ensure your drivers are always up to date.

How to verify your defrag was successful

After spending money on a disk defragmenter program and running the software to help optimize your computer, it’s nice to have a way to verify that everything worked properly. If you have compatible software, the easiest way to verify this is by opening up the program and looking at the current map of your hard drive. This visual should show you the location of your files and how they are currently distributed. Luckily, it shouldn’t be difficult for users to understand.

If the defragmentation was successful, you should see your files all together in a singular area of your hard drive. If the defragmentation was not successful, you will likely see files scattered across the entire disk. Here, you should be able to view original and newly-moved data, ensuring it’s all on the ideal part of your computer’s hard drive.

Another way to check if your defragmentation worked, although not quite as definitive of an answer as opening up the software, is to see if the overall performance of your computer has improved since you ran your most recent defrag. If things seem to be running faster and more smoothly, and it feels like you can access and open files more quickly, it could mean that your defrag was successful.

Mike Jennings

Mike Jennings has been a tech journalist for more than thirteen years, and he covers a wide range of topics, from gaming laptops and graphics cards to consumer software, business machines and high-end desktops. He’s written for PC Pro, TechRadar, Wired, Stuff, TrustedReviews, Custom PC, IT Pro, and many more outlets. He lives in the UK and is interested in gaming, writing and motorsport.