Replace Missing Favicon

This extension was abandoned over a decade ago and the developer hasn't and won't be making any fixes or updates. By default, this extension only works on http sites. To make it work with https sites, you will have to make a copy of this extension and edit it. But even after doing all of that, this extension still will not work with some https sites. For the instructions on how to copy and edit this extension, scroll down and read the review written by Tracy Cooper Jr on Apr 30, 2018. It is a painful process though. The extensions folder is really difficult to get to and find. Once you find it, you have to make a copy and place the copy somewhere else, and make sure the copy never gets deleted. Then edit the copy. I also think that the favicons are a bit of an ugly eye sore. They look nooby and could look better. I thought that the extension only replaced the tab favicon, but I guess that it will replace the bookmark favicon too. It just takes a while for the bookmark favicon on the bookmarks sidebar to update.

only works on sites that are not https

It works but I had to make one change for it to work on https sites. Copy the extension directory to a new location. Open the contentscript.js file in the new location and scroll to the bottom. Change http://www.gravatar.com/avatar/ to https://www.gavatar.com/avatar/ and save the file. Open the extensions page and select "Load Unpacked" and select the new extension location.