Written by
Amanda WongAfter upgrading to macOS Sequoia on MBP 16 inch M2 MAX with 96 GB RAM, occasionally CPU and RAM is eaten by 10 to 20 process named and starting with WebThumbnailExtension waiting is not solving the issue, I need to open activity monitor and force quit. What is the reason behind this? I have two studio displays attached to MBP in Clamshell mode with Apple Thunderbolt 4 cables.
Quite a few Mac users reported that their Mac ran slowly after upgrading to macOS Sequoia. After checking Activity Monitor, they found that the process WebThumbnailExtension uses a lot of CPU and Memory. Read on to find possible fixes for this issue.
Why is WebThumbnailExtension High CPU and RAM usage?
Many Mac users have experienced the same issue on their Macs, and the high CPU and RAM usage of the WebThumbnailExtension is noticeably slowing things down. Some think it is a Microsoft Office problem related to MS Excel or Microsoft OneDrive. While some other people find the WebThumbnailExtension high CPU and memory usage issue is triggered by the Quick Look.
It seems that there is no clear culprit of the WebThumbnailExtension issue on macOS Sequoia, the causes are different. Furthermore, given there has been no official response and many people are unable to figure out the true situation, it could be a glitch that will be resolved in a later version.
Reddit discussion on WebThumbnailExtension High CPU and RAM usage
The OP in the following post reported the same WebThumbnailExtension issue, WebThumbnailExtension Web Content keeps generating a lot of the same processes in Activity and hogs CPU and memory, and killing the process is a workable solution to make it normal.
In the comments section, another Mac user said that the extension is related to Quick Look, and disabling Quick Look temporarily can fix the WebThumbnailExtension high CPU and memory issue.
Possible fixes for WebthumbnailExtension High CPU and RAM usage
As we have explained above, the specific reason for the WebThumbnailExtension Web Content problem on macOS Sequoia is unclear, but it eats up a lot of CPU and memory causing the Mac to slow. Although there is no official solution, you can apply the following possible fixes.
Kill WebThumbnailExtension
You can manually kill all the WebThumbnailExtension processes in Activity to release occupied CPU and memory. This fix usually works when you encounter any other process that uses extremely high CPU and RAM on Mac. Here's how:
- Open the Activity Monitor from the Launchpad.
- Double-click the WebThumbnailExtension process and click Quit.
- Choose Quit again on the pop-up window.
Disable Quick Look
Disabling Quick Look works for some Mac users to fix the WebThumbnailExtension high CPU and memory issue, you can also try it out.
- Open the Apple Menu and select System Settings.
- Scroll down the sidebar and choose Trackpad.
- Select the Point & Click tab and toggle off Look up & data detectors.
Update MS software
If you find the WebThumbailExtension process using high system resources in Activity Monitor after you launch the MS software such as MS Excel or OneDrive, you can check available updates for MS software and update them to see whether the issue gets fixed.
Update macOS
The WebThumbnailExtension error could be caused by the macOS glitches, therefore, it could be solved with the latest/next macOS update. Here's how to check macOS updates:
- Go to the Apple menu and open System Settings.
- Select General from the left and click Software Update.
- Wait for it to automatically check the update, if there is an available update, follow the onscreen guide to update macOS Sequoia.
Help other Mac users fix WebThumbnailExtension high CPU and RAM usage!
