Open Bug 1417721 Opened 3 years ago Updated 1 month ago

tabs.Tab.favIconUrl intermittently returns undefined even though favicon is showing in tab


(WebExtensions :: General, defect, P3)



(Not tracked)


(Reporter: u462496, Unassigned)



(1 file)

This shows up eg, doing tabs.query.

I have had the opportunity to verify this does actually happen, though it is intermittent and I'm unable to give an STR.

This includes favicons served by http(s) URLs.

I have witnessed this with both discarded and loaded tabs.
Here is an extension used for polling the tabs in the current window and printing out the favIconUrl's to the console.  Just click the browserAction icon.
Priority: -- → P3
Product: Toolkit → WebExtensions
Bulk move of bugs per
Component: Untriaged → General
I am running into the same problem with my extension "IdentFavIcon Quantum" (, and I'm told that the Favioli addon has a similar issue in Firefox. The extension sometimes doesn't detect that the page already has a favicon and so overrides it. This appears to be completely arbitrary; any given tab may or may not have the favIconUrl set. A user reports ( I tend to agree--that the problem has gotten worse since Firefox 63. I'm considering uninstalling my own addon since this is causing too much confusion.

I'm a user of . I observed that this issue only happens on sites without <link rel="icon">.

Sites without <link rel="..."> to a favicon. The extension usually (not 100% of the time) thinks they have no favicon, and replaces with an identicon:

Sites with <link rel="shortcut icon"> or <link rel="icon"> and are unaffected:

The reason that identfavicon-quantum doesn't experience this problem on sites with a <link rel="icon"> is because it contains a workaround that explicitly checks for such a tag and disables itself on that page if it finds one. The underlying Firefox bug occurs regardless of whether or not the page has the tag; from bug reports and my own experiences it seems to disproportionately affect certain sites, but which sites seems to differ between users.

I can reproduce with identfavicon-quantum on

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