Safari and Safari Networking Using Excessive CPU, Safari Spikes CPU and Turns On Fans on New Mac mini, or High CPU Usage in Safari on macOS 27.0.1.

Confirm that you have sufficient free space on your internal storage. The absolute minimum is ~30-40 GB free space, and as a rule of thumb you should aim to have 15-20% of your total internal storage as free space. You can check the amount of free space you have on your Mac in a variety of ways:

• Select your internal drive then click File menu > Get Info, check Available space
• Go to System Settings > General > Storage, check the graphical display at the top of the settings pane
• In Disk Utility (in Applications > Utilities), by selecting the main container disk below the drive itself (you may need to select View menu > Show all devices to see it)
• In the System Report – hold the Option key and click the Apple menu > System Information (the top menu item), look for the name of your internal drive (Macintosh HD, unless you have renamed it as I did)

Note that on version of macOS prior to Golden Gate, the ‘available’ space reported with the first two methods above was greater than the ‘free’ space reported by the second two methods. Apple corrected that confusion with Golden Gate, and as shown in the above screenshot, the available/free space is consistent across the different methods. Those 'purgeable' data are also now included in System Data, accounting for the apparent increase you (and others) have noticed. You didn't lose space, macOS just categorizes things differently now than on Tahoe. For more details, see this User Tip.

Some steps to take to safely free up space:

Free up storage space on Mac - Apple Support

Optimize storage space on your Mac - Apple Support

How to free up ‘System Data’ and other st… - Apple Community

If nothing in the above reveals an obvious culprit, then appropriate troubleshooting steps are Safe Mode and creating a new user account to test. 

See if the problem is present when you boot in safe mode. That process performs some system cleanup and clears caches, and also disables 3rd party extensions that may cause problems.

Start up your Mac in safe mode - Apple Support

If that does not correct the issue, test in a new user account. A newly-created user account will have all settings at default, and if the issue does not occur in that new account then it provides guidance on what may need to be changed to correct the issue.

Add a user or group on Mac - Apple Support

Once the testing is complete, the new account can easily be deleted.

Delete a user or group on Mac – Apple Support

If you have 3rd party ‘protection’ software installed, that may be the problem. That includes:

• Cleaners (software claiming to automatically free up space)
• Optimizers (software claiming to make your Mac run faster)
• Antivirus software
• VPN software (unless provided by a school/employer to enable access to internal resources from a remote location)

Such 3rd party system ‘helpers’, ‘cleaners’ and ‘protectors’ do more harm than good. In fact, such products are completely unnecessary for macOS and the only ‘good’ (if you want to call it that) they do is to put money in the developers’ pockets. Cleaners and protectors cause compatibility issues, often after macOS updates. Commercial VPNs claim to hide your browsing activity from websites, and while that may be true those VPN providers just sell your browsing data to others. For the user, all of these types of software offer only harm…and if that is limited to harm to your bank account, then count yourself lucky. If you have installed such software, follow the developer’s instructions to completely uninstall it (note that some developers fail to provide instructions and their software installs can be pervasive, meaning the only way to truly remove it is to erase your Mac, reinstall macOS then restore your user files from a backup).

It might help to download and run EtreCheck, written by a long-time forum member. The free version is fine. Post the full report using the Additional Text button. No personal information is revealed. 

Personally, I have had no issues with Safari (or any other app running too hard) on macOS 27.0 or 27.0.1. I do have a more powerful Mac than yours (16" M4 Pro MBP, 48 GB memory), but Safari should not be bogging down on an M6 Mac mini.

Your new Mac Mini M6 appears to have a Safari-related performance issue. 

Opening Safari causes CPU usage to rise sharply, sometimes involving Safari, Safari Networking, RunningBoard, and processes associated with cdn.shopify.com. The CPU usage returns to normal when Safari is quit, while Brave runs normally. The underlying cause remains unclear.

Since you have no Safari extensions installed and have already cleared Safari history and website data, the most useful next step is to gather evidence while the problem occurs. 

In Activity Monitor, View >> View All Processes, identify the processes using the most CPU and capture a Sample Process report for the affected processes. Apple's Activity Monitor guide explains how to inspect them.

You could also run EtreCheck to look for potentially relevant background software or configuration issues. 

It provides additional context but may not identify the cause.

Download the Application Etrecheck  ( External Link ) directly from the Developer.

This is a Diagnostic Tool that makes no changes to the computer.

It makes a coherent and readable inventory of both the Hardware and Software used on the computer 

The application is free or paid for added features. 

The Report will Not Reveal Any Personal Information. 

Post back the Full Report - Share Report >> Copy , then  paste  >>>> using the Additional Text Icon  <<<<

To narrow things down, open Safari to a blank page and see whether CPU usage still spikes. 

Note whether cdn.shopify.com appears and which processes are affected. 

Its presence alone does not prove that Shopify is responsible. Testing Safari in a separate macOS user account may also help determine whether the issue is specific to your account.

Share these findings with Apple Support under your existing case and ask them to investigate the Safari issue separately from the System Data and purgeable-storage concern. 

Since your case has already been escalated, check with your support contact before making major system changes.

Although your observations point to a Safari-related problem, they do not establish a specific macOS 27.0.1 bug or confirm that a future update will resolve it.

Hi Melvin,

I had exactly the same issue twice in the past weeks (with Safari 27.0 on macOS 15.8.1).

The first time I fixed it by removing a given page from my reading list ("Liste de lecture" in French),

the second time by removing a given page from my favorites ("Favoris" in French).

I haven't figured out yet why some pages cause `Safari networking` to go frantic but it seems to happen.

I really hope this workaround will fix your problem.

Regards,

Aurélien

Thanks for the response. I’m definitely not low on storage space. I have a 512 GB SSD with plenty of actual free space available. The System Data issue is separate and something I’ve already spent quite a bit of time troubleshooting with Apple Support. The case was escalated to Apple engineers, who ran diagnostics and got back to me about a week later. On macOS 27, I’m seeing roughly 100–105 GB being classified as purgeable/System Data, especially when my external SSD is connected.

Apple Support has advised me that this behavior is normal and that macOS will reclaim the purgeable space automatically when necessary. I understand how that works, but I’m honestly really frustrated with how macOS handles System Data and purgeable storage. If I pay for a 512 GB SSD, I should be able to use the storage I paid for. I don’t think users should have to wait until the drive is close to full before that space becomes available again. Having roughly 100 GB tied up and effectively unavailable until the system decides to release it feels unnecessary, especially on a brand-new, Mac with 24 GB of RAM, very little installed on it, and no years of accumulated bloat or clutter.

The Safari issue is my bigger concern. This Mac is only about two weeks old, I have no Safari extensions installed, and I have already cleared Safari history and all website data. Despite that, simply opening Safari can immediately cause overall CPU usage to jump from roughly 1–2% to around 50–60%.

Safari itself, Safari Networking, RunningBoard, and Safari Web Content processes can all spike at the same time. One process that keeps appearing is cdn.shopify.com, sometimes using around 70–80% CPU. What I find especially strange is that even after clearing Safari website data, the Shopify process keeps coming back.

With Safari closed, Activity Monitor shows the Mac around 98% idle. Brave on the same machine can sit around 0.5–2% CPU even with multiple tabs open. Safari, by comparison, can make the fan come on just from opening it and sitting on the start page.

At this point I’m using Brave because the difference is dramatic. The rest of the Mac performs extremely well, so this appears to be specific to Safari rather than a general performance, storage, or RAM issue. I’m hoping this is something Apple fixes in an upcoming macOS/Safari update.