@Frederic
I do have a rather old Sony Xperia 1 II and Firefox don't use that much battery. See the screen (I'm using this browser a lot) :

@Aopen @firefox

@ozoned
Switch to #Firefox NOW !
@firefox

@n3er0o
Yeah, Yahoo! is pretty popular in Japan. I was really surprised when I went to Japan in 2016. Before that, I thought that Yahoo! was dead as a corp. I couldn't be more wrong...
@Sabata11792

@mertn
This.

Google can't be trusted now.
@monty33

@kratoz29
Is your Android phone on dark mode ? If so, Firefox will be on dark mode too.

If it's for the PDF, can't say, I don't think even Foxit Reader can transform PDF documents i'to dark mode ones on the fly (haven't tried on fact).
@QuazarOmega