HTML you can keep.

What it is

One file. Manifest, data, style, root, runtime — all inlined.

AI tools emit HTML by default: reports, dashboards, notes, demos. A Capsule is what that HTML becomes when it's sealed for keeping. The same envelope whether an LLM, a build script, or a human authored it — readable in five years, on any device, without a server.

How it's shaped

Five required blocks. Twelve rules. Zero ambiguity.

<!-- A valid Capsule, in outline -->
<script id="capsule-manifest" type="application/json">
  { "uuid": "...", "title": "...", ... }
</script>

<script id="capsule-data" type="application/json">
  { ... your snapshot, free-form ... }
</script>

<style id="capsule-style"> ... </style>

<main id="capsule-root">
  <!-- the readable artifact, pre-rendered -->
</main>

<script id="capsule-runtime"> ... </script>

What this is not

Three lines of fence-posting.