What is WebKitPluginHost?

I’ve noticed a process taking up a fair amount of memory on my Mac mini, running Snow Leopard: WebKitPluginHost. WebKit is Apple’s HTML rendering engine; it’s used by Safari, Mail (for HTML messages), and many other programs that display HTML pages. But I never noticed it before as a process. In addition, it’s currently taking up more that 200 MB of real memory. Does anyone know what this is?

Follow-up: interestingly, though not surprisingly, the process disappeared after quitting Safari. I think I figured out where it came from: I was uploading a file to my MobileMe iDisk when I noticed it. Perhaps that “PluginHost” is something that is needed by the special window that displays when you make an upload. I’m surprised that it used so much RAM, but I was uploading a file that was around 190 MB. Maybe it takes up RAM corresponding to the size of the upload… More testing will be needed.

Follow-up: it’s a process used when certain plugins are called by WebKit, including the Flash Player plugin.

17 thoughts on “What is WebKitPluginHost?

  1. Yes, that’s what someone else just told me. Interestingly, it seems to have been launched by using my iDisk, so Apple hasn’t updated whatever’s needed (or, the iDisk upload in Safari uses Flash or something else). It’s still a lot of RAM to use for a plug-in.

  2. I can replicate your finding. I don’t know what plugin it’s using but it’s not Flash – I have Wolf Rentzch’s excellent ClickToFlash installed and that doesn’t show a Flash object on the Mobile Me page.

    Since Apple is fanatical about only using web-standard technologies for its world-facing content, I would be astonished if this were done in anything other than HTML, CSS and JavaScript. I think there’s probably some dependency in the JavaScript code they’re using that requires 32-bit elements of JS or something.

  3. i’ve noticed it as well. every time it kicks up, my entire macbook pro locks up for 10-20 seconds, complete with spinning colour wheel. it also makes my itunes stall.

  4. Yeah ditto. Consumes gobs of memory and sucks up processor time. Hoping the first update takes care of this because it’s a real bust.

  5. i just started having the spinning-wheel-locking-up problem after installing the latest update for java from apple on my macbook. firefox, safari, itunes, quicktime, plex, all stall out. additionally, the optical out will flash, my speakers pop [sometimes quite loud] my volume slider fades to grey, and it renders my computer basically unusable for up to ten minutes at a time [so far]. my concern is that it continues this behavior long after all apps have been closed. why would this webkitserver be running when all i’m doing is listening to music in itunes with my wireless net disabled?

  6. I’d suggest you check in Activity Monitor (in your /Applications/Utilities folder) and see if WebKitPluginHost is running. I don’t see it when I’m using iTunes; only when I’m looking at Flash videos (or other animations) in Safari.

  7. strangely, the issue started with firefox [my main web browser] and i used safari to troubleshoot and it worked fine… for a bit. webkitpluginhost was running [according to istat nano] at the time i had only itunes open, however it may have been residual lag.

    i just updated firefox and haven’t had an issue yet. i’ve gone to some very flash-heavy sites and it seems to be in order. i’m cautiously optimistic at the moment.

    are you still having slow-down issues?

  8. It seems to have been improved with the last OS update.

    WebKitPluginHost may keep running after a browser has quit; it might not quit itself correctly.

  9. This error happens alot on Facebook using certain game apps. I get it often and only when in facebook playing one of the apps.

  10. switching back to Firefox… too much trouble with Safari… also ClickToFlash is causing problems in v4.0.5

  11. WebKitPluginHost showed up as the cause for my MBP switching from integrated Intel graphics to the nVidia card. Happened when I opened a page containing a Microsoft Silverlight app (www.kivabank.org)…


  12. I have Little Snitch installed and it notifies me whenever an app tries to ‘call home’. Webkitpluginhost spend a lot of time calling home, at least three tries for every new page. Somebody is getting a lot of information about where you go and what you look at.

    • I’m not sure that’s true. I just tried loading a YouTube video, and WebKitPlugInHost didn’t try to connect to anything. It’s possible that _certain_ Flash animations are sending cookies, and these cookies are well known, but it’s not WebKitPlugInHost itself that is doing this, but rather Flash that runs within that process.

  13. All Messages log:

    12/11/10 10:59:36 PM WebKitPluginHost[8955] Warning once: This application, or a library it uses, is using NSQuickDrawView, which has been deprecated. Apps should cease use of QuickDraw and move to Quartz.

  14. Hey guys,

    I just noticed the same thing with my memory being used by the PluginHost, but surely enough, each time I close a window or tab in Safari that had flash on it, it dropped in chunks straight away.

    Safari is really starting to annoy the crap out of me. Sometimes on my MBP, Safari will beach ball for a bit loading the Apple webpage…

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