Favicon shows on a browser tab but not on a bookmark in Firefox

Question

As in the topic.

I created a 32x32 favicon.ico file and put it into a project folder. This icon shows nicely on a browser's tab but when I drag this tab to bookmarks icon changes to a terminal icon.

I run page locally with flask development sever and Firefox.

I tried different locations and formats with the same effect.

I suspect some Firefox's settings needs to be changed because Chromium and PaleMoon are fine.

Any ideas where else to look? This is just an annoyance but any help will be appreciated. Thanks.

Answer 1

Favicons in firefox are loaded dynamically that is each time you open a tab, this has been a bug about it until recently this study was released this showed that favicons are capable of tracking browsing activity as favicons are saved by other browsers to local disk, then firefox made it a feature;).
Later supercookie was released and showed the proof of concept working.

But to answer your question firefox loads then each time when connecting to the server which was a bug, which now is a feature to have the favicon retrieved opening eachtime.