[css-image-animation] Applicability of image-animation to the poster image of video elements

[frivoal]

In the January discussion of the image-animation property, it was suggested that we may want it to apply to the poster image of a <video> element: if the <video> element is in a state where the poster image is displayed, and if the poster image is itself an animated image, then you'd be able to run/pause/stop it using this property.

Filing this issue to confirm if this is what we want.

We did not resolve at the time, but making it apply seemed to be the consensus at that time.

An alternative theory would be to say that the poster image of a <video> element isn't really considered an image as such, animated or otherwise, but rather a piece of UI of a complex element, and that the image-animation should not have effects on UI interactions, so it wouldn't apply.

[css-meeting-bot]

The CSS Working Group just discussed [css-image-animation] Applicability of image-animation to the poster image of video elements, and agreed to the following:

• RESOLVED: image-animation applies to <video> poster images

The full IRC log of that discussion

<TabAtkins> florian: does image-animation apply to a video's poster image?
<TabAtkins> florian: seems the room's opinion was yes, it's an image
<TabAtkins> florian: counter-argument is it's not an image, it's a UI state
<RRSAgent> I have made the request to generate https://www.w3.org/2026/03/31-css-minutes.html fantasai
<TabAtkins> florian: we didn't quite resolve on it
<ChrisL> q+
<TabAtkins> florian: Do we want to resolve that it applies?
<TabAtkins> yes
<astearns> ack ChrisL
<TabAtkins> ChrisL: I think if we allow it to apply, users can choose whether they want it to apply or not
<ChrisL> s/apply or/animate or
<TabAtkins> RESOLVED: image-animation applies to <video> poster images
<TabAtkins> (florian, look at https://github.com/whatwg/html/issues/12318)

[Crissov]

Does this resolution effectively mean that all current and future image-… properties should affect video poster images?

The Images module specifies all the others at the moment.

• image-animation
• image-orientation
• image-rendering
• image-resolution

It does not seem to explicitly mention objects – sensible to object-… properties – that may have two (or more) different concrete representations based on (loading/playing/…) state or timeline. (It does mention icons as an example of different spatial representations within one resource.)