Screenshot!

Memory usage will vary based on many factors, your computer, length of time Firefox is open, sites you are visiting, extensions you are using, other programs on your computer, etc. The only time to worry about it is if the memory usage is causing issues (slowdowns, or not releasing when it's done).

There's some steps you can take to reduce memory usage:

• Update Mac OS to the latest version
• Ensure Firefox stays up to date
• Try a Firefox refresh Refresh Firefox - reset add-ons and settings
• Firefox uses too much memory or CPU resources - How to fix may include some other tips

You can try to modify multi-process settings to see if this has effect.

• set number of content processes to 1 if it is currently set to a higher value (4)
  Options/Preferences -> General -> Performance
  remove checkmark: [ ] "Use recommended performance settings"

See also:

• https://support.mozilla.org/en-US/kb/performance-settings