Signal Open Graph Preview

Signal builds a link preview on the sender's device and routes the request through a privacy proxy. The card puts the image first, then a bold title, a short description, and the bare domain underneath.

Signal reads the Open Graph title, description, and image from the initial HTML response and ignores twitter:* tags. Without og:image it falls back to the page's apple-touch-icon or favicon, shown as a small thumbnail beside the text; so is any image under 200px or roughly square. A clear title and a wide image that still reads when cropped do the most work.

Signal only supports links that start with https. A disabled link-preview setting, a page that blocks the request, or metadata that is not present in the initial response can leave the message as a plain link.

Previews are generated before a message is sent and can be removed from the composer. If a page has changed, paste the link again after fixing its metadata instead of relying on an older preview.

Set og:title, og:description, and og:image in the page head. Use an HTTPS image at 1200×630 when possible, keep it under 5 MB, and serve it without an image redirect.

The scanner requests both the page and its image with Signal's preview user agent, so it can show whether the tags are reachable before you send the link.