Animated favicons

My favicon used to be animated. Well it still is but it simply doesn't animate anymore in Firefox, only displaying the first frame. If you don't know what a favicon is, it's the name for the icon next to the tab for the webpage. It's short for favourite icon and was originally created for bookmarks(favourites) to be able to quickly distinguish websites from a list. On mobile it should show up when scrolling through the tabs you have open or looking through your bookmarks. Interestingly it still animates for me on the bookmark toolbar, but not on the browser tab.

It's never animated on Google Chrome or Microsoft Edge. I don't have a way to check but it wouldn't have worked for Safari either; so no other browser allows animated favicons. The Wikipedia article says that "Various browsers such as Firefox and Opera support animation of favicons", however the citations only apply to Firefox and I suspect this isn't true for Opera since there's no citation for it and the other ones for Opera predate 2013, which is when Opera changed from their custom browser engine to Chromium^[0] . So now animated favicons are fully dead in all mainstream browsers.

A favicon is specified with the following HTML:

Interestingly there is a reference to the icon in the HTML specification for the link element but most of it is left up to the user agent^[1] . "Icons could be auditory icons, visual icons, or other kinds of icons." It would be cool to have an auditory favicon or even the vague "other kinds" but I doubt that could be done in a way that's acceptable to users and web developers. Most of this specification is the kind of spec that retroactively describes the behaviour that already existed rather than building a specification from scratch for a coherent, consistent and easy to use API so it's intentionally vague since different browsers already have their own behaviour in this regard. It's also not the kind of area that would cause developers too many compatibility issues.

The old firefox bug on their bug tracker for disabling animated favicons is this one from 2001, staggeringly from 24 years ago. Sharp-eyed readers will notice that (as of 2026-04-07 at least) the bug is still open though and hasn't been updated in over a year. So what happened? Where did it get changed? I went looking through the source code of Firefox to see how and why it was changed. For GIFs not animating, I found this set of code changes which is linked to this bug. The gist of the change is that programs will often have multiple processes since it improves security using sandboxing. The program can give one of the children lower permissions so that even if there's a vulnerability in it and an attacker can run arbitrary code that code can't escape the process and cause a serious security flaw. The change here was to render the favicon image in the child process that loads it rather than the main browser process^[2] . However it simply renders the first frame which means that GIFs will only show that first frame now. I thought this was unintentional but after searching through the Firefox bug archive I found that I was not the first person to notice this change. This bug was raised and the author of the change earlier commented on it that it was an expected change from the other bug and it was closed.

My favicon was not a GIF though, it was an animated SVG using CSS animations to scroll the text. What caused my one to stop animating? I tracked this one down to this change related to this bug which is doing a similar thing to the raster image change but for SVG images. Note that you can change browser.tabs.remoteSVGIconDecoding in Firefox's about:config to false and still see the wonder of my animated favicon. At least unless either that gets changed or my favicon gets changed.

Some other people have noticed this change, I did find this reddit thread where someone is confused why their favicon isn't animated/ so I'm not totally alone. It would be nice if Mozilla had mentioned somewhere that they were changing this feature, including on that original bug report from 2001 since it shows up fairly high on search. Here's a few reflections on this.

1. I shouldn't have been using an animated favicon. I mostly did it because I could and I like to experiment with things on this site and the primary user is me. However it is a poor user experience for a similar reason to animated text being annoying, except this is even more egregious since it applies anytime you have the tab open.
2. You could technically still animate the favicon manually by using Javascript to code the image and update it. I would never do this because it's a waste of time and it would be fighting against the browser which I don't really want to do. I want to use modern and convenient idiomatic HTML, CSS and Javascript as and when needed. Some web applications do change the favicon by putting notification icons on the favicon when there's something for them to check. This isn't quite what favicons are intended for but it isn't too far against the grain of how they work.
3. Google Chrome leads all browsers' development since it's the most used browser, and the underlying engine Chromium is even more widely used. This means that any features that only exist in Firefox are not cared about since it would only be usable for a small percentage of all web users. This point isn't a novel one but it's worth mentioning.
4. The change to improve security is a good one overall. Browser security is really important since so much of our interactions happen over the web and it is supposed to be safe to browse untrusted websites. They're so important that they get a huge amount of effort used to break the security and because there's so many features on the web and the code needs to be high performant there are inevitably mistakes causing security issues. Image decoding is a significant part of this, there being many different formats and decoders for images and plenty of them being written in unsafe programming languages, so moving favicons to be decoded in a child process which is less privileged provides an extra layer of security. You can view these links to see just how many security vulnerabilities there are in Chrome and Firefox that get found.

Finally, I need a new favicon. I've never known what to use for profile pictures on any platform so I tend to use whatever images I think are cool. It would be nice if I had something consistent and interesting.

Footnotes