Used to work like a charm, and for some sites it still works. But most of the time it doesn't work anymore, and you just see a blank page without the changes visible.
When you visit the Github page of this project, you see why, the add-on isn't maintained for a long time (almost 5 years) and the developer says he is not able to maintain it anymore.
Unfortunate because it was a great project, which really worked fine.

WOW! I've been searching for tool like this for a long time. Thank you!

Used to work, but just fetches empty pages...? And worse, randomly deletes the alerts that I've added with no apparent cause.

"Click this Panel" Doesn't work in Win11/FF117

Sadly, given the lack of response to any of the security related pull requests, I have to conclude this once useful extension has been abandoned. Thanks for years of usefulness.

I use firefox more than chrome because of this extension

I like it very much. As many others say, it would be nice to be able to set a shorter than 5 minute refresh time when you have system resources to spare and want to be first to a site change. It integrates with Notification Sound (another Firefox add-on) so that it plays a sound, and you can choose a nicer one from C:\Windows\Media. It would be cool if it would also send notification emails, or integrate with a future "Notification Emails" (which does NOT exist) since the site I am following is updated at midnight and my PC is a long way from my bed. It does not let us choose a part of a page so pages that have changing adverts are fraught. Fortunately that does not apply to me. All in all, a very nice extension which provides functionality that you would have to pay for from update notification website services. Thank you Sneaky Pete.

I have been using it more than five years almost daily with no problem at all.

Excelente!!

Helps me reliably to track changes of important web sites.

Good app, but the minimum autoscan time is 5 minutes, couldn't find how to make it run checks more often (1 min or less)

This was a brilliant add-on for many years. In the last days I get no updated page changes even though they have been scanned. No error message either. Have tried installing the extension on another PC with the same result.