CA Cards

Cards makes the share image for pages on my sites: the 1200 by 630 picture that appears when a link is shared on Mastodon, Bluesky, Slack, or iMessage. Each card is drawn from the page itself. A blog post shows its title or opening words, its date and categories, and its first photo, and a short post with a wide photo sets its words over the photo. A Weekly Thing issue sits on its cover photo with its summary and its count of links and journal entries. An Another Thing episode shows its number and running time. A saved link on Linking Things shows its title, its site, and the issues that carried it, with my note when the note is mine.

I built it with coding agents on October 24, 2026, after deciding against Micro.blog’s own card styles. I wanted the full canvas, no photo of me, and the blog’s type in black and white. The blog came first, that same day. Weekly Thing, Another Thing, and Linking Things followed on October 25, each with a card of its own.

Each page names its card in its share-image tag, with a short hash of what the card shows, so an edited page gets a new card. The first request for a card runs a Lambda function that reads the page, lays the card out with Satori, and renders it with resvg; CloudFront then keeps it for a year. It draws only the card a page actually names, so it cannot be used to make any other image. Cards with a photo are JPEG, to stay under Bluesky’s 1 MB limit, and emoji are drawn from Twemoji.