about:performance, an internal page in Firefox that shows which tabs open in windows are consuming how much, has been updated to give a clear picture on which tab/page is using more CPU cycles.
Firefox new about:performance
To try it out, ensure you’re using the latest Nightly version,
1. Visit about:config
2. Find and change preference dom.performance.enable_scheduler_timing value to true.
3. Close and relaunch Firefox and visit about:performance to see the new look.
Warning: Close Firefox and reopen it after flipping the preference, otherwise the browser will crash and you’ll see Mozilla crash reporter dialog.
Update: The Preference has been enabled by default.
Old and new about:performance page change: ‘Performance of Web Pages’ wording has been changed to ‘Resource Usage per tab’
Depending on usage, the page may display Energy Impact for a tab as high or medium or low or None.
Use can select a row with mouse in about:performance page, double-clicking a row selects the tab.
UPDATE: New Firefox about:performance page to feature memory column in Firefox 65 and Control Center to show ‘Energy Impact’ and ‘Memory footprint’ for individual pages and More sub-menu Hamburger menu to contain Task Manager item.
Image credits: Mozilla
Hamburger menu with More sub-menu contains Task Manager item, which opens about:performance page.
UPDATE: As said above, Mozilla has added Task Manager item to ‘More’ section of Firefox menu in version 64 Nightly to open about:performance page.
BTW, if you type about:p in address bar, about:performance will be auto-filled, read Firefox 64: Autocompletes about: URLs in address bar.
