Mac Tutorials

Disk Defragmentation: Do You Need to Defrag a Mac?

If you're an experienced computer user, or you used to have a Windows computer, you might have relied on disk defragmentation as a way to optimize your computer’s performance. Moreover, Windows OS has always included built-in defrag software.


But what if you’re using a Mac? macOS (previously Mac OS X) doesn’t come loaded with any sort of a disk defragmenter. (However, it has Disk Utility and Apple Diagnostics to fix your Mac’s hardware).


So what should you do? Is there a way to manually defrag your Mac’s hard drive? Is it necessary to do so and is it safe? Find all the answers in our article.


Before we start


From our experience, we can condidently say that  defragmentation isn’t the only way to optimize your Mac. It’s also not a magic pill to increase the speed of your Mac. The more you ignore optimizing your Mac, the harder it may become to correct its operation at a later date. So it’s necessary to optimize your Mac’s performance regularly.


Get MacKeeper and optimize the productivity of your device in a few clicks! With our app, you’ll always know when your Mac needs optimization.

What is disk defragmentation?

Defragmentation is a process of organizing files on a hard drive so that parts of large files are grouped together. This way it’s easier and faster to read a file.  


To understand why disk defragmentation might be useful for an HDD, let’s find out how data is stored on a computer.


As we mentioned before, data on HDDs is read and written on a rotating disk with a mechanical needle. Reading and writing data at the beginning of the hard drive is the fastest, and as you move inward, things get slower, since the needle needs more time to reach the data. That’s why the data is usually written on the faster (outside) edge first and then makes its way to a slower inside part of the disk.

What happens when you add a new big file?

The computer will store some of these big files in the free space at the edge of the disk until it’s filled up and then store the rest of your file elsewhere on your hard drive. This process is called fragmentation.


In contrast, defragmentation makes sense for an HDD, where data is accessed with a physical movement of a magnetic head. However, for an SSD, it isn’t beneficial and may be even harmful. Let’s see why it is so in more detail.

Why is defragmentation good for a PC but not for a Mac?

Windows tries to use the faster area of the disk and writes new data to the recently freed sectors in this area. This sometimes leads to significant fragmentation of a file. It means a file can be divided into 8 or more fragments, written into different drive sectors.


Our experts explain that reading such a file takes more time because the system needs to access several sectors to read it. Due to this algorithm, Windows needs to be defragged from time to time.


But macOS stores files differently on a hard drive. It uses two file systems: HFS+ (macOS 10.12 Sierra and earlier) and APFS (macOS 10.13 High Sierra and later). Both of them have some features that make storing of files more effective:

  • macOS file system doesn’t use the recently freed space on the outside of the disk to store data. Instead, it finds a larger area of free space to write a whole file there, avoiding fragmentation
  • macOS gathers smaller files into the larger areas on the disk and automatically defragments the files inside the group
  • macOS file system identifies often-used files and moves them into the hot area of the disk for fast access
  • macOS automatically defragments the files that are stored in more than 8 different sectors.

Due to this working principle, macOS doesn’t usually need defragmentation. This is why Mac optimization software doesn't usually include defragging as a feature.


Here’s how to check what kind of file system your Mac has:

  1. Go to Applications in Finder
  2. Select Utilities
  3. Select System Information
  4. Select Storage.
Knowing what type of file system your Mac uses is important to defrag your computer. Go to your Utilities folder and find System Information there
Step 1. Open System Information tool from the Utilities folder
In the System Information window, you’ll be able to move to the Storage section again. This time, pay attention to the File System line, highlighted with the red box.
Step 2. Click on the Storage tab > File System

Should you defrag a Mac?

Will defragging a MacBook do it any good? Here’s a short answer:


Do you have an older Mac with an HDD storage?

Do you have a modern Mac with an SSD storage?

Should you defrag your Mac?

Not really, but you can. It won’t harm your Mac.

No, it might be harmful for your Mac.

How to find out whether you have an HDD or an SSD

An HDD (hard disk drive) is an older type of storage device equipped with a rotating disk and magnetic heads, which read and write data to the disk. Among the recent Mac models, only certain iMacs come with HDDs.


An SSD (solid-state drive) uses flash memory to store information and doesn't have a spinning disk inside. This kind of storage device was introduced in a MacBook Air in 2008 and was increasingly used by Apple ever since.


It’s easy to check what type of drive your Mac has:

  1. Go to the Apple menu in the upper left corner of the screen
  2. Select About This Mac
  3. Go to System Report
  4. Go to Storage.
The system report about this Mac shows the key information about the device, in the Overview tab. Look at the Startup Disc line as the main focus in terms of defragging your computer
Step 1. Open the Overview to see the storage device on your Mac
Even more detailed information about your Mac’s storage can be found in the Storage section from your left panel menu. Under Physical Drive, you’ll see the current device name
Step 2. Click on the Storage tab > Physical Drive

When does a Mac need to be defragged?

In some situations, defragmentation may help your Mac hard drive run faster. For example, if you frequently work with media files larger than 1GB, defragmentation may be helpful. While macOS automatically defrags smaller files, it doesn’t do so to larger files, so they may be significantly fragmented.


Based on our research, the built-in algorithms in macOS handle arranging files fairly well and your Mac will only need additional defragmentation if it’s really old.


macOS doesn’t come with a utility for defragmentation and there’s no Terminal command for doing this either. But, if your Mac is really old and running slow, you can still defrag your hard drive by installing third-party software. Choose the one you like the most and follow the instructions provided by the developer.

Can defragmentation harm a hard disk drive?

The short answer? No. Defragmentation isn't harmful to hard drives (HDDs), and sometimes may be quite helpful and effective for slow computers provided you perform it correctly.


Defragmentation arranges the data and makes it more accessible, and it is safe for an HDD. It won’t remove or damage your data in any way.

Why is defragging an SSD a bad Idea?

If you own a Mac equipped with a solid-state drive (an SSD) instead of an HDD, you should never defrag it.


An SSD operates differently with its own maintenance routines. It simply doesn’t need defragmentation as it has no mechanical parts and your Mac can reach each sector at roughly the same speed.


Moreover, an SSD has a limited number of read and write cycles, and defragmentation is actually a process of reading the data from one sector and writing it to another. So, defragging an SSD will shorten its lifespan and lead to its deterioration.


1. Do Apple computers need defragmenting?

The short answer? No, they don’t.


In our team’s opinion, Apple has for storing data as whenever you edit a file, the whole file gets written out to a new space with enough room. In other words, this method prevents data fragmentation.


Moreover, macOS file storage technology ensures moving your most frequently used files to the edge of your hard drive (the fast part), which significantly boosts your Mac performance and speed.

2. How long does a disk defrag take?

Well, it depends on a lot of factors such as:

  • Your RAM size
  • Amount of files needs to be defragmented
  • Free space on your hard disk
  • The priority of the defrag process
  • Your Mac optimization algorithms.

As you can see, defragging time can really vary from a computer to another. However, if you're looking for an approximate number, then it can take around 60 minutes to defrag a 500 GB drive.

3. Any alternatives to defragging a MacBook Pro?

If your Mac isn’t that old and you don’t work with large media files, but the machine is still running slowly, here are some recommendations:

  • Install the latest updates for your macOS and don’t forget about updates for your software
  • Clean unnecessary files from your computer
  • Stop apps from loading at startup.

MacKeeper can help you do it all (and more) in just a few clicks! Optimize your Mac’s performance and forget about defragging your computer. 

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