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!

No doubt that this is a great addon, and very useful.
There should be some option to go back on the page as main back button doesn't work with sidebars, that's why I removed one star. I understand this still is a pre -release version so may be they resolve such issues before final release. Thank you Firefox.

Unfortunately firefox doesn't allow multiple side bars, so you can't use this alongside TreeStyleTabs to have two browser panes with one tab sidebar :(

great productivity booster!

打开的网页都是pc端的

Side View is a pre-release (major release 0.4. ...) and is presented as part of the pre-release Test Pilot project. This misrepresents Side View as a completed product when it is not.

have not got started yet

This is a great Addon. So far so good.
Feedback
In any YouTube video, I can't find horizontal scroll bar. Also there are two huge horizontal black bar. (What I'm trying to say is that the Addon is unable to adjust according to the video's aspect ratio.
Again, great Addon.

very useful extension :)

Love this feature, thanks! Am so glad I discovered it. A bit concerned that Firefox Test Pilot seems to have ended (before I even discovered it). Hope that this excellent add-on does not disappear.

Great tool for developers! You can see the desktop and mobile versions of a page in one window.

An excellent tool. So useful across so many situations. One of the best is the ability to have my password manager available full time in the sidebar while updating logins. Or simply, anytime I want to keep an important site open and visible while doing other things. Should be a standard feature.

Great tool but still need enhancement. Hope that a refresh, back and next page item will be added to the right-click context menu when click on side view.