Link Previews

[jyasskin]

Lots of social and messaging applications generate previews of links. There are a few specifications for the components of the pages that contribute to these links (https://developer.x.com/en/docs/x-for-websites/cards/guides/getting-started, https://ogp.me/, https://oembed.com/), but no open forum for discussing extensions and no standard for how consumers should combine the available data.

Search engines also generate previews, but I suspect we want to avoid trying to standardize what they look at, both because it's much more complex, and because the relationship with sites is more adversarial.

[tomayac]

The arguably most open one of such specifications is schema.org, for example https://schema.org/WebApplication, https://schema.org/WebSite, and https://schema.org/WebPage. Here's an example from one of my Web apps, SVGcode:

[csarven]

Just a brief braindump:

Perhaps obvious but I presume the initial distinction to be made here is between the concept of a preview - essentially an image, which may be animated - as opposed to an embed (iframe/object) which may be interactable.

Although limited, HTML's poster attribute for the video element is conceptually similar to link previews.

Is the consideration here about the publisher expressing a default link preview image, e.g., along the lines of <a href="http://example.org/" preview="http://example.org/image.png"> or <a href="http://example.org/"><img rel="schema:screenshot" src="http://example.org/image.png" />, and so that the user-agent displays it? Otherwise, I presume user-agents have an implementation specific feature to fetch the target resource and overlay a preview of it when for example the user hovers a link.