Block-based content models: why every modern CMS converges

There is a quiet convergence happening in publishing tools. Open Notion, Linear, Sanity Studio, Ghost 5, Substack — they look different, but underneath they all model content as a typed array of blocks. Markdown is becoming a transport format, not the storage format.

¶What blocks unlock

• Static analysis: a callout has a tone; a code block has a language. The renderer can reason about that.
• Multi-target rendering: web, RSS, email, mobile app — all from the same payload.
• AI-friendly: LLMs emit structured JSON cleanly. Markdown rounds-trips badly through them.
• Migrations: add a new block type without rewriting the parser.

{
  "version": 1,
  "blocks": [
    { "type": "heading", "level": 2, "text": "Hello" },
    {
      "type": "paragraph",
      "content": [
        { "type": "text", "text": "This is a typed block." }
      ]
    }
  ]
}

You can still author in markdown if you want — just compile it to blocks at write time. The storage format wins by being typed, queryable, and renderer-agnostic.