After waiting for my mid-2012 MacBook Pro to update for two days and nights, it’s finally on the latest macOS — 10.13 High Sierra!

As a tech enthusiast, I was excited about High Sierra and its new features. However, the excitement has been gradually overcome by the issues I encountered — mainly, that it runs slowly or even freezes up during and after installation.

Having immersed myself in countless Apple communities and forums, I found that I wasn’t alone. Because of our collective experience, I figured it would be a good idea to write an article listing common macOS High Sierra slowdown issues together with relevant solutions.

My goal is simple: to save you time solving problems! Some of the issues below are what I personally suffered, while some come from stories of other fellow Mac users. I hope you find them helpful.

Also Read: Fixing macOS Ventura Slow

Important Tips

If you have decided to update to High Sierra but have yet to do so, here are a few things (based on the order of priority) I highly recommend you check out in advance so you can avoid potential problems.

1. Check your Mac model – Not all Macs, especially old ones, are able to upgrade. Apple has a clear list of which Mac models are supported. You can view the specifics here.

2. Clean up your Mac – Per Apple, High Sierra requires at least 14.3GB of storage space to perform the upgrade. The more free space you have, the better. Plus, it’ll take you less time to back up. How to clean? There are lots of manual things you can do, but I recommend using CleanMyMac to remove system junk and Gemini 2 to find large duplicates. That’s the most effective solution I’ve found. You can also read our detailed guide on the best Mac cleaner software.

3. Backup your data – It’s always good practice to backup your Mac once in a while — or as they say, make a backup of your backups! Apple also recommends us to do that for major macOS upgrades, just in case. Time Machine is the go-to tool but you can also use advanced Mac backup apps which have some key features Time Machine doesn’t offer, such as bootable backups, the ability to select which files to backup, lossless compression, etc.

4. Update to 10.12.6 FIRST – This helps avoid an issue where your Mac keeps hanging in the “about a minute remaining” window. I found out the hard way. If your Mac is currently running an older Sierra version other than 10.12.6, you can’t successfully install High Sierra. You can learn more details from Issue 3 below.

5. Choose the right time to update – Do NOT install High Sierra at work. You never how long it’s going to take. Instead, I think it’s best that you set a time to do this on a weekend. The installation process alone will take about two hours to complete (ideally). Plus, it takes more time to clean and back up your Mac — and deal with those unexpected issues like the ones I encountered.

All done? Great! Now here is the list of issues and fixes you may reference in case of problems show up.

Note: it’s very unlikely that you’ll encounter all of the issues below, so feel free to navigate through the Table of Contents to jump to the issue that is exactly the same or similar to your situation.

During macOS High Sierra Installation

Issue 1: Downloading Process is Slow

Possible cause: Your Internet connection is weak.

How to fix: Restart your Internet router, or move your Mac machine to a better location with a stronger signal.

For me, it only took a few minutes for the download to complete before the installation window popped up. Here are two screenshots I took:

Issue 2: Not Enough Disk Space to Install

Possible cause: The startup disk on the Mac that High Sierra will be installed on lacks storage space. The latest macOS requires at least 14.3GB of free disk space.

How to fix: Free up storage as much as you can. Check the partition for large files, deleting or transferring them elsewhere (especially photos and videos which tend to take much more space than other types of files).

Also, unused applications could stack up. It’s good practice to uninstall them as well. The quickest way is to use CleanMyMac to deep-clean your hard drive and Gemini to find and remove duplicates or similar files.

For me, I didn’t encounter this error because my installation “Macintosh HD” has 261.21 GB available of 479.89 GB — 54% free!

Issue 3: Freezes or Stuck at A Minute Remaining

More details: The installation stops while the progress bar shows it’s almost finished. It says “About a minute remaining” (could be “several minutes left” in your case).

Possible cause: Your Mac is running macOS Sierra 10.12.5 or an older version.

How to fix: Take a few minutes to update your Mac to 10.12.6 first, then re-install 10.13 High Sierra.

I was really annoyed by this “About a minute remaining” issue — though it said only a minute left, a few hours later the situation was the same. I canceled it, thinking my Internet had been disconnected and re-tried. But I was disappointed to see my Mac hang up again with the same error: Stuck at one minute left.

So, I opened Mac App Store and saw that there was an update request (as you see from the screenshot below, thankfully I still have it). I clicked the “UPDATE” button. In about ten minutes, Sierra 10.12.6 was installed. I then proceeded to install High Sierra. The “one minute remaining” issue never reappeared.

Issue 4: Mac Running Hot

Possible cause: You’re multi-tasking while High Sierra has yet to finish installing.

How to fix: Open Activity Monitor and find resource-hogging processes. You can access Activity Monitor by going to Applications > Utilities, or do a quick Spotlight search. Close those applications or processes (highlight them and click “X” button) that are over-consuming your CPU and memory. Also, read this Mac overheating article I wrote earlier for other fixes.

While I installed High Sierra, my mid-2012 MacBook Pro did run hot a little bit, but not to a point that it needed attention. I found that once I quit a few commonly used apps like Google Chrome and Mail, the fan immediately stopped running loud. I had to switch to my PC for work stuff during those two days, which wasn’t a problem for me, fortunately. 🙂

After macOS High Sierra is Installed

Issue 5: Running Slow on Startup

Possible causes:
  • Your Mac has too many login items (apps or services that automatically open up when your Mac starts up).
  • The startup disk on your Mac has limited available storage space.
  • The Mac is equipped with an HDD (hard disk drive) rather than an SSD (solid-state drive). In case you wondered about the speed difference, I replaced my MacBook hard drive with a new SSD and the performance difference was like night and day. Initially, my Mac took at least thirty seconds to start up, but after the SSD upgrade, it only took ten seconds or so.

How to fix: First, click the Apple logo on the top-left and select System Preferences > Users & Groups > Login Items. There you’ll see all the items that open automatically when you log in. Highlight those unneeded items and click the “-” icon to disable them.

Then, check whether or not the startup disk is full by going to About This Mac > Storage. You’ll see a colorful bar like this showing you the usage of your hard drive (or flash storage).

Clicking on the “Manage” button gives you a detailed overview of what types of files are taking up the most storage — which is often a direct hint as to where you should get started cleaning up your Mac.

For me, I didn’t notice much speed lag after updating to High Sierra, probably because my Mac had an SSD already (its default Hitachi HDD died last year) and it only takes ten seconds or so to fully boot up. Seriously, Macs with SSDs are much faster than those with HDDs.

Issue 6: Mac Cursor Freezes

Possible cause: You enlarged the cursor size.

How to fix: Adjust the cursor to normal size. Go to System Preferences > Accessibility > Display. Under “Cursor size”, make sure it points to “Normal”.

Issue 7: App Crashes or Can’t Be Opened upon Start

Possible cause: The app is outdated or incompatible with High Sierra.

How to fix: Check the app developer’s official site or Mac App Store to see if there’s a newer version. If yes, update to the newer version and re-launch the app.

Note: if the Photos app fails to launch by showing this error “An unexpected error has occurred. Please quit and restart the application”, you may need to repair the Photos library. This article has more information on that.

Issue 8: Safari, Chrome, or Firefox Slow

Possible causes:

  • The version of your web browser is outdated.
  • You’ve installed too many extensions or plugins.
  • Your computer is infected with Adware and your web browsers are being redirected to suspicious websites with intrusive flash ads.

How to fix:

First, run an antivirus to check if your machine has been infected with malicious software or Adware.

Then, check if your web browser is up to date. Take Firefox for instance — click on “About Firefox” and Mozilla will auto-check whether Firefox is up to date. Same with Chrome and Safari.

Also, remove unnecessary third-party extensions. For example, on Safari, go to Preferences > Extensions. Here you’ll see the plugins you’ve installed. Uninstall or disable those you don’t need. In general, the fewer extensions enabled, the smoother your browsing experience would be.

How to Improve Mac Performance with High Sierra

  • Declutter your Mac desktop. Many of us are used to saving everything on the desktop, but that’s never a good idea. A cluttered desktop can seriously slow down a Mac. Additionally, it’s bad for productivity. How do you solve that? Start by manually creating folders and moving files into them.
  • Reset NVRAM and SMC. If your Mac is not booting correctly after updating to High Sierra, you can perform a simple NVRAM or SMC resetting. This Apple guide, as well as this one, has detailed step-by-step instructions. Make sure you’ve backed up your Mac before doing this.
  • Check Activity Monitor more often. It’s normal that when you’re running certain third-party apps, your Mac could slow down or even freeze. Activity Monitor is the best way to pinpoint those problems. For those apps that have compatibility issues running with the latest macOS, check the developer’s site to see if there’s an update, or turn to alternative apps.
  • Revert to an older macOS. If your Mac is extremely slow after the High Sierra update, and there doesn’t seem to be any fixes, revert to a previous macOS version like Sierra or El Capitan.

Final Words

One last tip: if you can, postpone your High Sierra update schedule. Why? Because every major macOS release usually has issues and bugs, High Sierra is no exception.

Case in point: A few days ago a security researcher found a security bug “that makes it easy for hackers to steal passwords and other hidden login credentials from a user’s system…to give hackers the ability to access Keychain data in plaintext without knowing the master password.” This was reported by Jon Martindale from DigitalTrends. Apple responded fast on this by releasing 10.13.1 two days after that.

While macOS High Sierra slowdown issues are less important than that bug, I imagine Apple will take care of them sooner or later. Hopefully, with a few more iterations, High Sierra will be error-free — and then you can update your Mac with confidence.