How to Defrag Your Mac Hard Drive

Despite a reputation for speed and performance, MacBooks are not immune to slowing down with age — no computer is. Thinking back to your PC days, you may remember disk defragging your Windows computer as the go-to fix for lagging performance. But what if you’re using a Mac? Let’s take a look.

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What does a Mac defrag do?

A Mac defrag moves related bits of data on your hard drive together, so files and programs can load faster. Disk defragmentation reorganizes your hard drive’s files to make them easier for your computer to access. But defragging a Mac is rarely needed, because Macs can defrag themselves.

To know what a Mac defrag does, it’s important to understand how your computer stores data. Disk fragmentation occurs naturally on any hard disk drive (HDD). The way data is arranged impacts how fast it can be written or read from a drive.

For instance, when you save a Windows PC file, the data is written wherever there’s space on your drive. If the file is too large to fit in one area, it will be broken up and saved in multiple places. Your computer keeps track of where everything is located, but it will start to run slower as it looks for all the corresponding data needed to open a file or run a program.

Disk defragmentation takes all the bits of data scattered across the disk and puts them closer together, removing gaps that appear over time as you delete or add new files.

A fragmented disk (above) has scattered data. A defragmented disk (below) is organized.

Unlike with Windows PCs, defragmenting your MacBook isn’t the best option to get it to run better — and in some cases, it’s not an option at all. So, why don’t you need to defrag a Mac?

Why is Mac defragmentation so rare?

Since the launch of Apple’s operating system OS X 10.2 in 2002, Macs automatically prevent file fragmentation and can defrag themselves. Rather than save data to recently freed-up space like a PC would, Macs will place the file in a larger area with room to expand.

The HFS+ and the more recent APFS file systems used by macOS come with built-in processes such as Hot File Adaptive Clustering (HFC) and on-the-fly defragmentation. HFC groups frequently used read-only files together in a hot storage zone on the drive for quick access. As files are moved, the system defragments them. 

Nearly all newer MacBook models come with solid-state drives (SSDs), which don’t need defragmenting. But even older Macs with spinning HDDs tend not to fragment. You can read all about the differences between HDDs and SSDs in our dedicated guide.

Also, your Mac will automatically check whether a file is highly fragmented (stored in more than eight different sectors). If it is, the system automatically defragments it. If your Mac is struggling to open files or run apps, fragmentation likely isn’t the cause.

Macs come with Disk Utility and Apple Diagnostics that troubleshoot and resolve hardware issues. Rather than attempting a Mac disk defrag, you’re better off deleting files or doing a full reinstall by formatting your hard drive — making sure to clone your hard drive as a backup before you start.

Do I need to defrag my Mac?

Because of all the built-in functions mentioned above, you don’t need to know how to defrag a Mac because you probably won’t ever need to. Apple doesn’t even come with a defrag utility, and defragging can potentially wear out your drive. 

As a general rule, Macs don’t need to be defragged. Of course, like any rule, there are exceptions. You might need to defragment your Mac if one of the following applies: 

• Your Mac has a hard drive (HDD). Most modern Macs have an SSD by default or as an option, but older Macs and some specific iMac models have HDDs. 

• Your Mac is running out of storage space. If your hard drive has less than 10% of free space available, the operating system can no longer perform its auto-defragmentation routines.

• You frequently save large files (larger than 1GB) on your Mac. If you work with creative content regularly, such as audio, video, or design files, your drive is probably full of large files. While HFC can help keep file fragmentation under control, your Mac will eventually take a performance hit. 

If your machine is running slowly, check how much storage is available on your Mac, because it could be that your drive is running low on space. You can also test your Mac performance to see what’s causing issues so you can make improvements.

Never defrag Mac SSD

Can you defrag a Mac with an SSD? No, you should never defrag a Mac SSD. An SSD maintains its file systems automatically and does not have any spinning disk parts, helping it reach all files in roughly the same amount of time. SSDs also have a finite amount of write cycles, so you can shorten your drive’s lifespan when you defrag a Mac SSD. 

Upgrading your Mac to an SSD can help with slow startups, frequent system crashes, sluggish performance for apps that drain resources like Adobe Photoshop, and many other performance issues. 

Not sure what’s in your Mac? Here’s how to to check what kind of drive your Mac has:

1. Click the Apple menu in the upper left corner of your screen.

2. Select About This Mac and click System Report

   

3. From the left menu options, select Storage.

   

A Mac defrag should be used only as a last resort — and never for a Mac with an SSD. Instead, use a performance booster like Avast Cleanup for Mac to optimize your Mac SSD. Avast Cleanup finds and removes unnecessary files that are clogging your computer’s memory and filling up your hard drive so that you can get your Mac back to top speed.

Alternatives to Mac defragmentation

If you’re thinking about defragging your Mac, there are other methods that could help get your system moving faster. Generally, the HDD is not what’s causing problems. 

Here are some alternatives we recommend trying instead of a Mac defragment:

Step 1: Delete unnecessary system files and documents

Over time, Macs can become cluttered with thousands of files, application logs, and cache data. A drive always needs at least 10% of total drive storage to run background anti-fragmentation processes. 

Free up space on your drive by cleaning up your Mac. This can include clearing out cache files, deleting duplicates, or moving files you don’t use much into your iCloud storage. If you’re offloading things to the cloud, streamline your storage there and delete any files you don’t need from iCloud.

Step 2: Update your operating system and apps

Sometimes the best fixes are the simplest ones, like installing the latest version of macOS. System updates often include important performance and bug fixes for issues that cause slowdowns. You should also make sure all your installed apps are updated, as outdated software can also cause performance issues. 

You can check for and install updates by selecting System Preferences from the Apple menu and clicking on Software Update.

Step 3: Get rid of your unused apps

Like your closet, computers need spring sweeping to get rid of unused or unneeded applications. Learn how to completely uninstall Mac apps to permanently remove not just the apps but all of their corresponding files and leftover data that can take up space on your disk. 

Those are just a few ways to improve performance and speed up your Mac. Upgrading your RAM, swapping your HDD for an SDD, and updating your visual settings will all give you even better results.

Step 4: Repair file permissions with Disk Utility

Before you try defragging your Mac, think about cleaning up your Mac and repairing disk permissions with Disk Utility. File permissions ensure your apps can access the files they need, and if your computer is quitting apps unexpectedly or if you keep getting access errors, you may need to repair file permissions on your Mac.

Step 5: Use a specialized Mac cleanup tool

Do you find it annoying and time-consuming to manually delete unnecessary files, update your OS, and purge your Mac of all unused apps? Our dedicated performance engineers feel your pain. Avast CleanUp for Mac does it all for you — easily, automatically, and completely hassle-free.

Rather than spending time tidying up your Mac yourself or combing through your “Other” files in Mac storage trying to decide what to delete, let Avast CleanUp for Mac do it for you. We deep-scan your Mac for old junk files, documents, and duplicates — and once we find it, you can choose what to delete in just one click.

How to defrag a Mac

If all options above have failed to free up the space you need and you still want Mac defragmentation, here’s how to defrag a Mac and what you need to do so. 

1. Step 1: The safest and easiest way to do a defrag for a Mac is to use trusted third-party Mac defrag software.

2. Step 2: Backup your data using Time Machine, iCloud, or an external drive. If something goes wrong, you won’t lose any of your files.

3. Step 3: Install the defragmentation software that works best for your Mac and follow the on-screen instructions. 

As mentioned above, Macs don’t come with a built-in command or utility for defragmentation, and you shouldn't defrag a Mac if it has an SSD. 

It might be difficult to find Mac defrag software that works for an older Mac. If you’re running an operating system older than OS X 10.2, the latest defragmentation software for Macs won’t be compatible with your computer. Old Macs may also suffer from performance issues — you might want to check whether your hard drive is failing.

If you can’t boot up your computer and clear out your drive with cleaning software for Mac, another option is to wipe your old hard drive and do a complete reinstall. That’s the most effective solution if your drive is beyond repair — plus, it’s a way to defrag a Mac for free without needing to buy another program.

Boost the performance of your Mac without defragmentation

Your Mac accumulates a ton of junk over time, from temporary data and cache files to application logs and other useless data. If you don’t regularly tidy up your machine, your computer will start slowing down. And as we’ve learned, defragging your Mac won’t help.

Avast Cleanup for Mac keeps track of the hidden digital clutter that builds up, and makes it easy to free up space for the things you really need. It automatically scans your hard disk for hidden junk files, duplicates, and unused apps that you can then delete with just a click. It’s never been more convenient to optimize your Mac.