WebThumbnailExtension Web Content High CPU/Memory Usage

Problem still exists with Sequoia 15.3.1 update. I am running a 2019 iMac without track pad, so that's not the issue. Memory issues 'appear' to escalate when I am using Preview. If I go into Activity Monitor and click on the offending multiple WebThumbnailExtension Web Content processes and click 'quit' they remain open; I have to force quit them and then all is well.

Can Apple PLEASE address this issue as it's quite annoying to have processes freeze & crash due to lack of memory whenw in fact my iMac has oddles of memory in reserve.

I had my default browser set to Zen Browser (which is firefox based). In this case opening images in preview for example starts these pesky hogging thumbnail extension processes. As you state @bravebro, setting my default browser to safari fixes this specific problem. But still I want to not have to set my default browser to safari when I want to use something else.

I have exactly the same issue you have with Preview appearing to be the triggering culprit. HOWEVER I am using Safari as my usual browser, so in my case using Safari doesn't solve the issue. I see that there is a Sequoia 15.3.2 update just released today, but looking at the description it doesn't look like this issue is being addressed...

Update: 15.3.2 does NOT resolve the issue. Using Preview to open files whilst using Safari still causes the same RAM problems as before. Apple appear NOT to have resolved the issue with this latest update. Wonder if they ever will? Might be time to wipe the iMac and do a clean install of OSX 14

Further to the above, I have run an EtreCheck scan which highlights these issues. Hopefully someone at Apple will read this :-)

Diagnostics Information (past 60 days):

    2025-03-12 11:41:35 apfsd - High CPU Use (2 times)

        First occurrence: 2025-03-12 09:55:49

        Executable: /usr/libexec/apfsd

    2025-03-12 11:41:05 spotlightknowledged - High CPU Use

        Executable: /System/Library/Frameworks/CoreSpotlight.framework/spotlightknowledged

    2025-03-12 09:50:39 lsd - Crash (6 times)

        First occurrence: 2025-03-12 09:50:34

        Executable: /usr/libexec/lsd

    2025-03-11 16:22:05 com.apple.WebKit.WebContent - High CPU Use

        Details: 

            "com.apple.Safari"(1079)

    2025-03-11 15:55:57 com.devguru.DriverKit.SamsungMTP - High CPU Use

After I had the issue with my M1 MacBook Air over several OS versions, I encountered it again on a new MacBook Air M4 (with MacOS 15.3.2). Pretty disappointing that this does not seem to have been fixed up for years now.

After trying the various approaches discussed here and elsewhere (QuickLook, Browsers etc.), several times and with reboots, I closed office (Excel and Word) and eventually threw them from my disk. This solved the issue immediately. No WebThumbnailExtension Web Content since then...

I did a clean install of macos and it did not solve the problem. I do think it reduced the occurrences, but it still happens multiple times a day, so it's not a solution. Definitely something to do with spotlight's interaction with office.

help

I mainly appear during focused searches, and multiple searches result in

When I changed my default browser to Google Chrome, I had the same problem.

After changing the default browser to Safari again, problem get solved.

找到一个临时解决方案，暂时解决了这个问题：https://junki.cn/archives/Ag0GinQV

hi all.

I solved the problem by turning off the spotlight search index.

I just unchecked the "folders" line.

I suffered from this issue for more than a month. Now everything is ok.