Apple - How can I figure out which tab in Safari is using CPU?

  1. You need Safari 6.1 or newer

  2. Enable Debug menu.

Update: For Mac OS Mojave and newer, go to System Preferences > Security & Privacy > Privacy > Full Disk Access and add Terminal before entering the command.

    defaults write IncludeInternalDebugMenu -bool true
  1. Set "Use Per-tab web processes" and "Show Web process IDs in page titles" to on.


The Activity Monitor app provides entries for individual Safari tabs. You can search for “Safari” in it to see just Safari-related processes, including all its tabs, and sort by CPU percentage to see which ones are active.

Unfortunately, each process name only includes the domain of the URL, rather than the full URL, so it can be a bit tricky to work out which tab it is if, like me, you have lots of pages open from the same domain.

(I’m on macOS Sierra 10.12.6 and Safari 10.1.2; I’m not sure when this was introduced.)

Activity Monitor app, with process

For what it’s worth, I’ve checked both the Develop menu and the Debug menu in the latest (Version 5.1.4 / 7534.54.16), and couldn’t find any helpful features.

Develop menu:

Debug menu:

The debug menu can be enabled using the following command:

defaults write IncludeInternalDebugMenu -bool true