If you experience slow performance issues on your system while browsing the web with Mozilla Firefox, you can use the built-in Firefox Task Manager to quickly detect and manage system resource usage. See how you can use it.
In any Firefox window, click icon with the three horizontal bars in the upper right corner of the window and select More> Task Manager.
When the Task Manager tab appears, you will see a list of open tabs, each of which corresponds to a site you are browsing. At any time, you can click on the “Memory” or “Energy Impact” column title to sort the tabs by maximum to minimum resource usage.
To see the CPU usage of each tab, look at the "Energy Impact" column. You will see labels such as "Low", "Medium" and "High", along with numbers that measure the relative energy effect (higher numbers mean more energy consumption). The tabs with the highest energy impact will reduce your computer's CPU performance, they will use more electric power and will exhaust it battery a portable device faster.
To see how much RAM each tab uses, look at the "Memory" column. Typically, you will see memory usage in megabytes (MB). If you see very high numbers here, this one is likely website or tab to slow down your machine.
If you see a small black arrow next to any tab in the list, click it to see an extended list of subframes and trackers used. Some sites call external websites provide them with additional functionality or send data to networks advertisements Which can use the resources.
After clicking on the arrow, you might be surprised to see all the trackers and subframes that some sites include in their code.
Finally, if you want to close an annoying tab, select it in the list, and then click the "X" button on the far right of the row.
The tab will close. You can close as many tabs as you want this way, which can also be a handy quick way to manage a colossal list of open tabs. Good luck!
Source of information: howtogeek.com