The developers at Mozilla have decided to remove the "about: performance" service page, which allows you to track the CPU load and memory consumption created by processing various pages. The decision is driven by the introduction since the release of Firefox 78 of a similar in-purpose "about:processes" interface that duplicates the functionality of "about:performance" but is seen as more user-friendly and provides more information.
For example, the “about:processes” page not only shows the page titles, but also binds tabs and subresources to domains, and provides information about resource consumption by service processes and background workers. One of the advantages of the "about: performance" to be removed is the ability to separately track the resource consumption of add-ons. The "about:performance" interface is already called by default when selecting the "More Tools -> Task Manager" menu. After "about:performance" is removed, an attempt to open this performance page will result in the display of the "about:processes" interface.
Source: opennet.ru
