Firefox has some major issues with favicons right now but this is the closest I've got to sorting it out. It recovered a ton of them. It doesn't work on links that are no longer active (which makes sense), so some of the problem might be your bookmarks themselves.

old but gold!
478 bookmarks took 7:39 min

i work a lot with the bookmarks and sort them in directories. Also i often reinstall Windows and test some Linux distros, which means i also do often sync fresh Firefox/Waterfox instances.
The addon opens every bookmark in your current window (focus remains on your current tab and your opened tabs stay alive. maybe 5 proccessing bookmarks at a time)

Excellent overall, the only thing I spotted is that there is no way to disable the warning check for "canonical". Should there be an option to disable this function would be most helpful.

I recently converted from Chrome to Firefox after many years. I had 6097 bookmarks without favicons. After ~45min, I had favicons for the majority of them (the remainder were no longer working sites).

I would give this extension 6 out of 5 if I could. Just imagine updating 6000+ URLs one at a time !!!

Such a great, useful, minimal add-on. Thanks for your work!

i have delete my favicons.sqlite file and rebuild it with Checkmarks, but not all of my bookmarks have get their favicon, but why?
For such cases i use now additional this Add-on: https://addons.mozilla.org/de/firefox/addon/cache-favicons-for-bookmarks/ but this can also not update all favicons by unknown reasons ... the funny is, firefox itself shows in this cases the favicon in tab but not the bookmark!

Is it possible to make a add-on version which also works on mobile firefox (Android)? Here you don't have any favicons, this looks simply "poor" :-(

I love this addon add it to all me browsers if you can find it for others

I simply love this extension, I've been trying to merge and clean out 23 years of favourites coming from many many browsers, jobs, and stages of my life, thanks to this one I was able to do it, yes I had to review tons of broken and old links but at the end and after hours this extension helped me to get the job done, thanks so much.