Branded link previews in Slack, iMessage, and LinkedIn.

A link that unfurls into a blank grey rectangle looks broken, and people click it less. NudgeHost generates a proper preview for every hosted file. The thumbnail is built from the file's own content rather than a generic placeholder, so the card actually shows what is on the other end. The mechanism is the Open Graph image, and open graph images explains how the tags in a page tell Slack or LinkedIn what to draw in the preview card.

What each app shows depends on the app, not on extra work from you. Slack renders a full unfurl card with the title, a line of description, and the thumbnail. iMessage shows its rounded link preview with the image. WhatsApp and LinkedIn read the same tags and build their own version of the card. Because the preview comes from standard metadata, you set nothing per platform. You paste the link and the receiving app fills in the rest.

The thumbnail matches the file. When you put a PDF online, the preview shows the first page, so a proposal looks like a proposal in the chat. When you host an image, the card shows a scaled version of the picture. An HTML page gets a generated screenshot of the rendered result. And when you swap the file without changing the URL, the preview regenerates from the new file, so the card never shows a stale version of something you have already revised.

One quirk is worth knowing. Chat apps cache previews hard, so after you swap a file the old card can linger in Slack or iMessage for a while until their cache expires, even though the link already serves the new file. The previews come with every plan, and the free plan only governs the limits around your links rather than whether they unfurl. If a preview ever fails to show, it is usually the receiving app's cache rather than the link itself.