If Firefox is using an unexpected amount of RAM, report a bug by following the steps below:

1. Open about:memory in a new tab.
2. Click Measure and save…
3. Attach the memory report to a new bug
4. Paste your about:support info (Click Copy text to clipboard) to your bug.

If you are experiencing a bug, the best way to ensure that something can be done about your bug is to report it in Bugzilla. This might seem a little bit intimidating for somebody who is new to bug reporting, but Mozillians are really nice!

If you prefer not to open a bug, you can instead reduce the number of content processes used by Firefox to a lower amount by going to about:config and changing dom.ipc.processCount.webIsolated to a lower number.

Please help, I cant watch videos!

You could always disable hardware video decode acceleration and continue to watch videos.

Please report issues: https://firefox-source-docs.mozilla.org/performance/reporting_a_performance_problem.html