To me, the only Screenshot Addon that really works (only tested on Firefox Desktop Version!).
It does what you hope for:
1 continues, big picture - in a small fileformat - without external servers - advertisements - or a heavy addon with several megabytes!
Sleek - working - FOSS - I love it!
Thank you Manuel!

still the best, simplest and versatile screen shot saver, many thanks to M-Reimer

This add-on work incredibly well on Firefox for Android!
A must-have add-on before FFfA has its built-in screenshot feature like the desktop version.

Mozilla Firefox 135.0b1 — OK.

This add-on is perfect. Although Firefox already has a screenshot feature, this add-on is very straightforward and offers various but simple options. I have it set to take screenshots in JPG format at 90% quality, and every capture comes out with excellent image quality and without much file size. Yesterday, I also discovered an option that lets you add the date, hour, minutes, and seconds to the screenshots exactly how you want! Thank you! :D

Work so good (Firefox mobile).

It's a add-on that does its job.

So helpful for firefox android! Please check it for security as well, Firefox team.

Es exactamente lo que estaba buscando. Funciona muy bien ya que guarda el sitio web tal cual como se en el navegador. Cuando hay partes de un sitio web que contiene un video, la captura puede tomar cualquier frame de éste, pero eso es un detalle. Muy buena la extensión.

So far, so good. I don't know if it has a shorter way to capture the screen, but you can choose from full, viewport and selection in PNG or jpeg. And the best feature is it names the capture! So it saves me from putting each name. Yeah!!!!

Enfin un module de screenshot qui fait juste ce qu'on attends de lui, et qui ne nous fait pas passer par 5 écrans pour avoir un simple screenshot de la page entière. Fonctionnalités minimales, on peut même le configurer pour exporter la page entière directement dans nos téléchargement sans avoir à faire plus que cliquer sur l'icone. Juste parfait.

Good enough I put the effort into making an account to leave a 5 star review. This is the only one I could find that does what it says it does and does it properly.