[Tip] How to Restore Classic “About:Performance” Page UI in Mozilla Firefox

In newer Mozilla Firefox versions, Mozilla developer team has replaced the old classic about:performance page with a new Task Manager page which now shows list of all opened tabs and add-ons and their energy impact. You can access this page using about:performance URL in address bar or using Firefox main menu (Hamburger menu) -> More -> Task Manager option.

Following screenshot shows the new Task Manager (About:Performance) page in action:

We told you about new Task Manager UI long time back in UPDATE 126 when this feature was under development and testing.

On the other hand, the old classic About:Performance page used to show a simple formatted list of all running tabs with buttons to close and reload tabs. Following screenshot shows classic About:Performance page in action:

If you are using newer version of Firefox web browser and don’t like the new Task Manager UI (User Interface) of About:Performance page, you can restore the classic About:Performance page in Firefox using this tutorial.

Fortunately Mozilla has provided a secret preference to enable/disable the new About:Performance page UI in Firefox. So interested users can enable the new UI or restore the classic UI of About:Performance page using the hidden secret advanced configuration “about:config” page.

If you also want to bring back/restore the good old classic UI of About:performance page in Mozilla Firefox, following steps will help you:

1. Open Mozilla Firefox and type about:config in the addressbar and press Enter. It’ll show you a warning message, click on “I accept the risk!” button.

2. Now type scheduler_timing in Search filter box and it’ll show following preference in the window:

3. If the preference value is set to true, it means new Task Manager UI of About:Performance page is enabled. If the value is set to false, it means the old classic UI of About:Performance page is enabled.

To modify the preference, double-click on dom.performance.enable_scheduler_timing preference and change its value. Alternatively, you can right-click on the preference and select Toggle option.

To enable new Task Manager UI of About:Performance page, set the value to true.

To restore good old classic UI of About:Performance page, set the value to false.

That’s it. The changes apply immediately.