I've been looking for a replacement for the default RSS previewer since it was removed from Firefox. Most extensions require opening a sidebar or contain features I will never use.

The author states that "This extension attempts to recreate.." the original previewer. I'm happy to report that this extension is nearly indistinguishable from the original.

I would rate it more than 5 stars if I could.

If you are looking to replicate the default reader's preview functionality, this is the add-on you need.

Thank you to the author for making it!