What To Do When Your Mac Slows Down

Posted on by Larry

I was chatting with Olivier today who was suffering through a long bout of SPOD (you know, the “Spinning Beachball of Death”). That got me thinking about what causes life on your Mac to slow down.

Editing video is one of the hardest things you can do on any computer because it requires every piece of hardware and software to work at their best. If your system was working well, but is now slowing down, it’s time to figure out what’s changed.

Are you seeing slow render times, choppy playback, dropped frames or unstable software? The more precisely you can define the problem the easier it is to find a solution, because there are a lot of places to look.

While hardware can and does fail, hardware failure is not the cause of most problems. When we work with large media files the data transfer rate, called “bandwidth,” is most important. This is the transfer speed of moving a file from one place to another and is generally measured in MB/s (MegaBytes per second).

File transfer speed is actually dependent upon several factors:

In general, technical problems are most often the result of insufficient bandwidth caused by bottlenecks in the media, the operating system, software, or hardware. Let’s take a look at each in more detail to give you some ideas to get your system working better.

NOTE: If you just had a hard disk crash, or your system is dead or unresponsive, don’t bother with this or any other tutorial. Call Apple Tech Support immediately. If the drive is from a 3rd-party manufacturer, call them first. Many drives can be salvaged if you DON’T try to repair them first.

While you may think that hardware should be the first place you look, there are other spots to check first; and that starts with your media.


Storage Location

In general, projects, media and render files should all be stored on your fastest drive. While you can use the internal drive on your computer, my recommendation is to store them on external drives, ideally SSDs or RAIDs.

First, this makes it easy to move projects between computers. More importantly, though, is that the internal drive is supporting a LOT of activity: the operating system, background processes and foreground applications. Use the internal drive for temporary work files, and external storage (ideally attached using Thunderbolt) for everything else.

NOTE: Activity Monitor (located in the Utilities folder, illustrated above) is great way to see all the different applications running concurrently on your computer. There are dozens! This is why I recommend using external storage for your media and projects. It isn’t as busy as the internal drive.

Stock Images & Footage

Stock media is notorious for causing problems. If you are using stock, try removing it from your project and see if rendering and playback improve. Also, get in the habit of transcoding stock media into ProRes 422 before bringing it into your project. Not all companies and individual providing stock media are as careful about their settings as you are.

Render Files

Render files are the second largest cause of problems. Before you delete them and re-render, which I’m going to suggest next, verify that render files are stored on a fast drive with enough space to hold them. Sometimes, the default settings in your NLE store render (or “generated”) files on a slow drive. Make sure you are storing all render files on a fast drive.

Then, delete all your render files (also called “generated media”) and re-render. This often fixes problems that crept in; many times caused by bad stock footage. There’s no harm re-rendering, except for the time it takes. Use this as an excuse to get another cup of coffee – or, even better, walk around the block.

Render times that seemed positively peppy when editing 720p media will seem glacial when editing 6K files. Why? Pixels. A 720p frame contains 921,600 pixels. A 6K frame contains 19.9 million, an 8K frame has 39 times the pixels of a 720p frame – 35.4 MILLION pixels! Those giant frame sizes will slow rendering on any computer.

And, as you would guess, the more frames per second, the more pixels need to be rendered. Notice that even 4K projects are processing hundreds of millions of pixels per second!

Frame Size & Frame Rate

Most systems can easily edit HD media, but choke when the frame size increases. This is especially true when editing large frame sizes compressed using H.264 or HEVC media. It’s important to set your expectations as frame sizes and frame rates increase.

If your system chokes on large frame sizes, switch to editing proxies. Proxies are at least 1/2 the size of your camera masters and compressed using an editing friendly codec; my recommendation is to use ProRes Proxy as your proxy codec, not H.264.

Both Premiere and Final Cut transfer effects from proxies to source media automatically, so you don’t need to worry about copying effects.

Here’s a chart that illustrates the size – in MB/second – of ProRes files as the frame size increases. A system that can easily edit smaller frame sizes may collapse under the deluge of pixels in larger files.

NOTE: This is also true when frame rates increase. Storage data transfer rates increase 2.5X when frame rates go from 24 fps to 60 fps. For example, ProRes UHD 24 fps is 59 MB/second. ProRes UHD 60 fps is 147 MB/second. Most spinning hard disks can support the first rate, but not the second.

HEVC Media

H.264 media is highly compressed. HEVC (H.265) is compressed even more. It takes a powerful system to smoothly edit HEVC media. Newer systems (like the M1 Mac) have built-in HEVC decoders in hardware, which makes editing this media smoother and easier. Older computers are don’t have that capability.

If playback stutters, see if your camera source files are HEVC (most iPhone video uses this format to save storage space). If they are, optimize the files during import if you are using Final Cut, or transcode them into ProRes or DNx or Cineform if you are using Premiere before importing the files.

The disadvantage to optimizing your media is that the resulting files are about 6X larger than the source files, so you’ll need to make sure you have enough storage space. But the smoother playback and faster rendering will more than make up for it.

H.264 Media

If you have a system that’s more than six years old, it may also have problems playing H.264 media. The reason is that newer systems include hardware acceleration of H.264 media for editing, which older systems lack.

If you are having problems playing H.264 media (often labeled, wrongly, as MP4 media) try optimizing or proxy files, as described above. Yes, storage needs will increase, but editing will be much more responsive.

NOTE: There’s no free lunch. You can’t have an easy-to-edit video format that is also a small file size. Small files are highly compressed and suitable for distribution. Easy-to-edit files provide extremely high quality, but create very large files. As the triangle above illustrates, there are three options with different media formats. We get to pick two.

Bandwidth Need Varies

One last point on media and bandwidth. The more clips that are playing at the same time – for example, multicam edits or interviews with B-roll – the more bandwidth you’ll need.

For example, let’s say you are editing a four camera multicam edit using UHD (4K) ProRes 422 media at 30 fps. Each angle is a separate video file requiring about 74 MB/second. So, four streams needs a minimum system bandwidth of about 300 MB/sec.

Then, because your NLE is doing more than just playing media, I add a 20% overhead for everything else going on with your edit. This means, in the case of our example, that you should have storage that supports at least 400 MB/second bandwidth for your edit.

Don’t assume that because your system can handle a single video stream that it can handle multiple video streams just as easily.

NOTE: In the illustration above you can see the advantages of using proxy files. The chart references ProRes Proxy at 50% size (1920 x 1080). While a single drive may have problems playing all 12 streams at once, it would not have problems with the data transfer bandwidth required. My recommendation is to always use RAIDs or SSDs if you are doing extensive multicam editing.


Most of the time, macOS is a very stable platform for media editing. However, there are three places where playback can go off the rails.

Upgrading Too Soon

Apple, like every developer, works hard to release stable products. But operating systems are unbelievably complex. With all the hardware and software available today, the interactions between them and the operating system are vast. Good QA testing and extended beta periods are designed to find problems and fix them before they reach the general market.

But it is impossible to catch everything before release. Especially those devilish “it only happens sometimes” kind of bug. Those drive everyone nuts.

The solution for editors is not to upgrade when the latest version is released. My general rule is to hold off upgrading any system used for deadline-based media production until Apple releases a .1 upgrade. This delay does two things:

  1. It allows Apple to fix bugs found by internal testing and early adopters.
  2. It allows 3rd-party developers to fix bugs – or work with Apple to fix bugs – caused by the new operating system.

The key idea here is that, as video editors, our job is to create programs people want to watch on-time and on-budget. No where in that sentence does it say we need to be beta testers of unreleased software.

Feel free to test new releases with computers that aren’t used for production. But I can’t begin to count the number of times a desperate editor contacted me for technical support because they upgraded too soon and now can’t export their project. That’s a level of stress none of us need.

The OS Goes “Ker-flooey!”

I am convinced that gremlins lurk inside my computer, just waiting to spring at the worst possible moment. You have two powerful tools to attack those gremlins:

It continues to amaze me how many problems can be solved simply by saving your work and restarting your computer. After you get done swearing, restart before doing anything else.

If you have an older computer, running an earlier version of the macOS, here’s link on how to get your system running again.

Next, Apple has a powerful storage repair utility hidden, but ready to run. Here’s a link that tells you how it works.


There are many things we can do to trouble-shoot problems in both Apple Final Cut Pro and Adobe Premiere Pro. Rather than repeat them here, these are the links:



There are two aspects of your storage that determine its speed: how you connect it to your computer and the storage system itself. The connection determines the size of the “data pipe” that your data flows through. The storage hardware determines how full that pipe will be.

For example, connecting a single spinning hard disk to your computer via Thunderbolt 4 provides a very big pipe, but that single disk is nowhere near fast enough to fill it. Here is an illustration of how bandwidth changes based upon how your storage is connected.

Ideal Data Transfer Rates By Storage Connection Type
Connection Data Transfer Speed
ThunderBolt 3/4
About 2,800 MB / second
ThunderBolt 2
About 1,400 MB / second
USB 3.1 Gen 2
About 1,000 MB / second
10-Gig Ethernet
About 1,000 MB / second
USB 3.1 Gen 1
About 450 MB / second
1-Gig Ethernet
105 MB / second
FireWire 800
70 – 80 MB / second
Formats Too Slow to Use
USB 2.0
10 – 15 MB / second
FireWire 400
20 – 25 MB / second
iSCSI 75 – 95 MB / second

But the rubber meets the road when we combine the speeds our storage can deliver with the speeds required by the media we are editing. Here’s an example.

This chart illustrates the approximate data bandwidth provided by different types of storage. For example, a single spinning hard disk isn’t fast enough to reliably support editing 4K media.


An extremely useful utility for both spinning media and SSDs is Alsoft’s Disk Warrior. This utility optimizes disk directories to improve both reading and writing data. I recommend it highly and suggest you run it every month or two.

NOTE: Disk Warrior does not currently support M1 Macs, or APFS systems. While this is an excellent utility, it is currently best used for older systems.

Link: https://www.alsoft.com

In the past, we were told to defragment our drives from time to time. While this is helpful for spinning media it should NOT be done for SSDs. They store data in an entirely different way. My recommendation is not to worry about defragmenting drives.

It is true that SSDs have a shorter life span than spinning media. However, both technologies will reliably work for years.

It is a good idea to boot into Recovery Mode and run Disk Utility First Aid once a month or so on your internal drive.

LinkRecovery Mode: A Better Way to Repair Your Mac


There’s no single solution to playback problems. That’s because video editing requires your entire system to be running at its best, and for you to know the impact of different media formats and frame sizes on your system.

But, once we’ve spent the time to get our system optimized, a smoothly-running system allows us to get back to what we love: telling stories with moving pictures.


Here are some additional resources you may find useful:

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6 Responses to What To Do When Your Mac Slows Down

  1. Rich Edwards says:

    Hi Larry,

    In your chart showing approximate maximum bandwidth by device, are the PCIe SSD and 4 drive PCIe SSD RAID 4 bars labelled correctly? Should these lower bandwidth bars be labelled SATA SSD and 4 drive SATA SSD RAID 4?

    Thank you


  2. JohnIL says:

    Not as impressed with M1 Mac’s as I was at first. I bought a Mac Mini and had my share of issues with Thunderbolt ports and external storage. Even internally I have found that the storage isn’t that great, and the systems needs more then 8 Gb RAM for some reason. Never had this issue with my Intel Mac’s. Since you cannot upgrade anything, I would strongly advise maxing RAM to 16 Gb or better and even consider a bigger SSD unless you plan to buy a compatible external drive.

  3. Gregg Kubera says:

    The “No Free Lunch” graphic reminds me of an old band slogan…from MANY years past.
    (but most likely still true!)

    “Clean…Sober…On Time ! (pick any two) “

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