Current (110.0.1 64bit) Firefox on a Del Inspiron 7415 2-in-1 laptop running Windows 11 Home x64 build 2261 with an AMD Ryzen 5 5500U with Radeon Graphics, 2100 Mhz, 6 Core(s), 12 Logical Processor(s) and 8GB RAM (type not specified in System Info).
With nothing but an empty Google search page loaded in a single tab, Firefox is using over 500MB of RAM. Same view, Edge is using less than 400. If I load Reddit or Facebook in the same tab, nothing else open, usage in FF jumps to over 800MB, and I noticed it at almost 2GB of RAM usage at times. Meanwhile, Edge never gets much above 500MB with the same usage.
I have not (yet) compared to any of my other PCs, an older low end desktop unable to go higher than Win10, and a months-old mid-range new-with-Win11 desktop simply due to use patterns and when I can use them for extended amounts of time.
Active extensions installed in FF:
Add To Any
Don't Accept image/webp
Enhancer For Youtube
New Tab Override
Reddit Ad Remover
Scroll To Top
WebP / AVIF Converter
Same or similar are installed in Edge except for Facebook Container, Scroll To Top and Tab Stash.
About:Processes in FF shows that the memory usage is with the main FF process, the collected/combined entry for extensions is relatively low, less than 200MB.
If further info is needed for troubleshooting (debugging, trace logs, etc), please also advise on how to get that info.