It currently has a bug that causes it to trigger sometimes when I click the back button. I just visited the page a minute ago, it works fine when the addon is disabled, and my internet connection is fast, so I don't think it's a problem with the site.

However, apart from the bug, this is indicative of a problem with the addon design, which is that it redirects to a different page, and offers no option to exit out of the addon or try to load the original page even if the Wayback Machine addon thinks it's broken. It's okay for the addon to make mistakes, it's not okay for me to need to disable it in order to load the original page.

It will be better if this extension have a auto show option

This extension worked great for a long time, only showing the 404 detected popup when I actually encountered a missing page. However, I recently updated from Firefox 56 to Firefox 63 (which may have updated the extension too), and that caused the extension to start detecting spurious 404s, as other reviews describe. When this extension works, it is a convenient way to open the WayBack Machine, but I’m going to have to disable the extension for now until it gets fixed.

On older Firefox versions I used to use the add-on Resurrect Pages by Anthony Lieuallen. I stopped using it because it became incompatible with my Firefox version, but apparently it supports the latest Firefox version again. It may be worth checking out.

It's nice to be able to look up or save a page from the button. The automatic feature might be helpful if it was not a false positive 95% of the time. An option to turn that off would be worth a star to this review.

Useful, but there are too many cases where are page just happens to load too slowly for the extension's taste so it pops up offering to use the service, blocking the entire page.

It would be nice if it would really only show up when the page is 404 and not because the page is coincidentally loading slowly.

A nice extension. Generally works but occasionally has hiccups.

That said, updating to the newest version needlessly cluttered up my context menu with duplicates of the stuff available through the browser action (that I currently have to resort to userChrome.css to remove) and non-optionally added a requirement for notification privileges with no option to turn off whatever annoying popup it's planning to display.

I'm giving it a 3 out of 5 for those warts.

Please don't change the URL. Please. That's horrible UX, makes me want to disable the extension right away.