Right away I found this extension useful! It's easy to figure out and very helpful. The only thing I would add if I could was the ability to save the highlighted text to some sort of notepad for later.

I agree with visiteur668. Excellent tool. Very usefull. Thank you.
The improvment I would suggest is bar icons (or special keys stroke) in order to select/change colors and highlight selected text with a single click (as it was possible with Prostetnic highlighter... where selected colour icon indicated selected colour without the need to check from the menu). Right click menu needs at least two clicks).

Works well ! Thank's.

The improvment I would like is a menu (or special keys stroke) in order to select/change colors (as it was possible with Prostetnic highlighter...)... Also a menu icon appearing in the menu bar would be welcome :-))

I could not quickly find any better/other extension to highlight text that is saved automatically in the same file (I use Zotero to save interesting websites but a highlight feature is missing there).

After a few reloads, I can confirm that Persistent Highlighter seems to do the job on the latest Firefox version.

I suggest to put the highlight options directly into the right click context menu and not in a subsection. Then it would be so much faster to use.
Of course, ideally there should be an option to switch marking on so that any selected text will be highlighted instantly.

It is interesting that such a fundamental function like instant highlighting seems so hard to implement - well, I am glad at least this add-on exists - thank you for that!