postmarketOS and Arch wiki? That's very weird, aren't both plain mediawiki? Works really well on my Firefox. Even works on SeaMonkey.

EndeavourOS/Manjaro forum probably uses Discourse... I don't get why people like that forum software :/

Archlinux site has been targeted by a DDoS attack recently and apart from that it always works great on any browser/engine

Manjaro forum maybe,but postmarket os site and arch wiki is static sites for me it's working very fast in firefox

Most sites run as well, if not better, on Firefox for me.

If you're running a quick and dirty test, you might not get an accurate picture of the performance differences. For example:

• Your usual browser might have cached some content from the last time you used it
• Unless you kill them properly, your computer might not have the RAM/processing to be running two browsers at the same time with the best performance
• One browser might be bogged down with extensions / issues that built up over time

You could try giving Firefox a clean install, or opening it in safe mode (it's now called troubleshoot mode), to see if there's any difference

In the 6 years I've been with Firefox on Linux on my 9-year-old laptop, I could count on both hands the number of sites that didn't render correctly, and on one hand the number that didn't run or weren't performant.

Maybe I'm just lucky, but I definitely feel for folks who are stuck with Chrome and all those ads.

??? Arch Wiki is just plain html and css? You might be experiencing the ddos arch services have experienced lately. In any case I've not had any problems on Librewolf, although out of the websites you listed I only regularly visit the Arch Wiki and occasionally the PostmarketOS site.

Chrome is just faster than Firefox. I use Firefox, but I do it despite its performance, not because of it.