Link preview checker

How it decides what each platform shows

Every platform falls back differently when a tag is missing, and that is where cards go wrong. The rules used here are the documented ones: the title comes from og:title, then twitter:title, then the <title> element. The description comes from og:description, then twitter:description, then the meta description. The image comes from og:image, then twitter:image — and if neither exists, there is no card image at all, which is what the grey panels above are telling you.

The tags are read by one endpoint that fetches the page and returns its <title> plus every meta element in the head. The image is then loaded by your own browser, which is the only way to measure it — those dimensions never touch a server. Built with the Hyperlambda Generator, and callable by your own agents over MCP. Run the platform yourself:

curl -fsSL https://hyperlambda.dev/docker-compose.yaml | docker compose -f - up

The whole backend, printed

No preview service, no scraping API. This page calls one endpoint, and this is that endpoint in full — generated from a plain-English description and verified before it was saved:

.arguments
   url:string
validators.mandatory:x:@.arguments/*/url
http.get:x:@.arguments/*/url
html2lambda:x:@http.get/*/content
.meta
for-each:x:"@html2lambda/*/html/*/head/*/meta/*/\\@content/."
   .name
   if
      exists:x:"@.dp/#/*/\\@property"
      .lambda
         set-value:x:@.name
            get-value:x:"@.dp/#/*/\\@property"
   else
      set-value:x:@.name
         get-value:x:"@.dp/#/*/\\@name"
   unwrap:x:+/*/*/*
   add:x:@.meta
      .
         .
            name:x:@.name
            content:x:"@.dp/#/*/\\@content"
yield
   title:x:@html2lambda/*/html/*/head/*/title/*/#text
   meta:x:@.meta/*

The property-before-name rule is the whole trick: Open Graph tags use property, Twitter and the classics use name, and a reader that only looks at one of them misses half the card. Describe an endpoint in a sentence, and the Hyperlambda Generator writes and deploys it — then it is a tool your own agents can call over MCP.

More free tools

Checking a link’s preview card is one of nine free tools here, each with the handful of backend lines that powers it printed on the page. See all of them — no signup on any of it.