Some websites make safari go crazy, and use 70% CPU! This causes everything else on this desktop to grind to a halt.

Is there a way to restrict safari to never go beyond a certain amount of CPU?

(btw - It's not just flash)

  • 70% of CPU usage shouldn't cause problems. There is not a single Apple computer sold nowadays with only one core, and that's been the case for almost a decade. 100% is not necessarily maxed out, 100% * the number of cores, is. I have a feeling something else is happening here than merely Safari overburdening your system. [joke] I bet your problem is Adobve Flash. [/joke] – Jason Salaz Oct 22 '12 at 21:00
  • 1
    You can restrain yourself from visiting heavy duty websites :) – Gerry Oct 22 '12 at 21:19

Enable the Debug Menu in Safari. One of the commands is Pause Web Process, another is Crash Web Process. Or the web process can be quit (or Force Quit) in Activity Monitor or any similar app.

And be sure to keep your Flash plugin current. Keep everything current/updated!


It is not possible to set the CPU limit for websites, but it is possible to limit the plug ins and extensions.

Disable things like Java and Flash Player .....

or for more serious use

Enable Safari’s Hidden Debug Menu

Quit Safari

Launch the Terminal and enter the following defaults write command:

defaults write com.apple.Safari IncludeInternalDebugMenu 1

Relaunch Safari

The “Debug” menu will be visible to the far right in Safari’s menubar choices. If you want to disable the menu, go back to the Terminal and type:

defaults write com.apple.Safari IncludeInternalDebugMenu 0


There are a few extensions that can help you.

ClickToPlugin is a great extension as it lets you block any plugin you want. While plugins run in their own processes, they often tend to be poorly written resource hogs (I'm looking at You, Adobe Flash!).

Any script blocker will do. There are several 3rd party scripts used by various websites that are not only annoying, they can also be huge resource hogs.

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