Signal generates link previews client-side on the sender’s device, routing requests through a TLS privacy proxy to protect the sender’s IP address. It identifies itself with the user agent WhatsApp/2, masquerading as WhatsApp to avoid being filtered differently. Signal reads og:title, og:description, and og:image from the initial HTML response and only supports HTTPS URLs.
This guide covers how Signal’s privacy-focused crawler works, which tags it reads, image requirements, its unique client-side caching model, and the most common issues that prevent previews from appearing.