Introduction

The Fedi Links Project exists to promote and support federated and decentralized protocols. In order to achieve this goal, the Project aims for feature parity with existing cross-silo interactions. One particularly popular way in which interactions across silos occur is through link preview cards. This specification defines link preview cards for web+* links, as otherwise migrating to web+* (for example, web+ap, for ActivityPub instances) would lose the preview cards, causing an UX regression.

Background

This specification builds upon Browsing Behavior of web+* Links, as well as existing cross-silo link preview cards, particularly OpenGraph metadata. However, no particular metadata protocol is enforced by this specification; OpenGraph just appears to be the most popular of them.

Generating the preview cards

The Well-Known Protocol Handler, as defined in Browsing Behavior of web+* Links, can be used to retrieve OpenGraph or other metadata for link preview purposes. When processing a web+* link, convert it to the Well-Known Protocol Handler before passing it on to the preview card fetching code.

Security Considerations

This specification carries no new security considerations than those already relevant to existing link preview systems.