Apple Messages (iMessage) generates link previews directly on the sender’s device rather than on a centralized server. This makes it fundamentally different from platforms like Facebook or Twitter, where a server-side crawler fetches your page. Because the preview is built locally, there’s no official debugger tool and caching behavior varies from device to device.
This guide covers how iMessage fetches your pages, which Open Graph tags it reads (and which it ignores), image sizing for different iOS versions, cache behavior, and the most common issues that prevent previews from showing.