it is great extension. Can not find nothing like that in Chrome

This works as advertised. You know how great a complement this statement is in these dark times!

I have two suggestions:

1. As practically all other folks here are demanding, the sidebar must be wider. If this is because Side View uses the built-in side view pane in Firefox, please, if at all possible, implement your own side pane and make it wider.
In case that's possible, why not more than one side panes simutaneously? Keeping two sidebars at each side would be very nice.

2. The Side View icon on the quick menu that appears at the top right corner by default. Currently its only real function is to switch between mobile/desktop view.
Please add that command in the context menus. Currently it has only one item (Open in sidebar), please change it to something like 'Open as Desktop/Mobile Site in sidebar' - so that if you click an empty space or tab, you could also choose how it will load. Then we could unclutter the quick toolbar if we choose to without sacrifice. Keeping track of sidebar-only visit history can be nice to some people, but I find it not very crucial.

very useful (i like it to keep the todolist or notes in sideview).

wishlist:
+ it would be nice to be able to drag tabs to sideview.
+ and in some cases a second (or even more) sideview can be useful, i.e. to use some columns to compare mobile views of sites or to view trello, notes, mobile site & desktop site together

Superb! Very useful add-on!
I hope that it continues to be developed. For example, to be able to drag it with no restriction. Or to have multiple pages that you can switch.

Awesome extension! Exactly what I was looking for to watch my email.
Add more futures plz
- open in a new tab not in mobile view
- back button
- multiple side views
- resizable more then 1/3 of a page

I use it to keep my task lists open alongside my email+calendar+etc, so it's really a huge help with my daily office work!

Fantástica extensión realmente práctica. Yo añadiría la opción de mostrar la versión de escritorio de las webs en el Sidebar y no solo la versión móvil.

This is an amazing idea and a very handy one. It should be not just developed but considered a Firefox essential piece.
It's great for web-mail checking, mobile version view, quick service checking, rapid social media posting, etc.
Hope it gets the attention it deserves.
Thanks a lot for such a great add-on!