1877274 - Favicons with "no-store" set in cache headers prevent them from appearing in bookmarks

Status: NEW

(Web Compatibility :: Knowledge Base, defect)

Description

[Ted Campbell [:tcampbell]]

When websites set cache-control: private, no-store headers we choose not to save them for bookmark or history purposes and the default icon is used instead.
Chrome seems to ignore the no-store aspect for this and has favicons in their bookmarks in more cases.

Comment 1

[Ted Campbell [:tcampbell]]

Bug 1598371 showed some downsides of not honouring the flag, but we do differ from the experience in Chrome and there are occasional complaints from users.

Comment 2

[Marco Bonardo [:mak]]

I think we're respecting the server request, by not storing the favicon in the icons cache. Imo Chrome is wrong, and the Web site should be fixed, I don't see a reason to use no-store in this case.
There are cases where effectively no-store is useful, e.g. showing a specific state of the web site or service in the favicon (of course the site must then also provide a static icon). As we cannot distinguish the two cases, either way we'll break something. And that's why I think the current breakage is the best option, as we're breaking wrong configurations, while in the other case (storing no-store) we'd break correct configurations.

To decide whether this issue is important, we could maybe add telemetry to measure how often it happens? Though that wouldn't be able to measure false positives, thus cases where no-store was used correctly.

The flooding would not be a problem either way, as we also stopped storing any icon set after the "pageshow" event.