Markdown twin
A clean low-token markdown version of the page for agents.
Why an agent cares
The same content in markdown costs an agent a fraction of the tokens and none of the layout noise. A twin that 404s, redirects to the HTML, or serves the wrong media type is worse than none, because the agent has already paid for the round trip. Point agents at it from the page, with a <link rel="alternate" type="text/markdown"> or the same relation in an HTTP Link header.
Adoption
Early production. Several independent organisations run it in production, though it is still niche on the open web.
Direction of travel: ▲ rising, as at .
Docs platforms serve markdown by default and Cloudflare shipped edge HTML-to-markdown conversion, but only 3 of 7 major coding agents actually negotiate for it (Checkly, Feb 2026).
| Adopter | Depth | Evidence |
|---|---|---|
| Mintlify | default-on | mintlify.com |
| Cloudflare (Markdown for Agents) | production | explainx.ai |
| Vercel (blog and changelog variants) | production | vercel.com |
| GitBook, HackMD | production | synscribe.com |
What we check
| Check | Severity | Raises | On whose authority |
|---|---|---|---|
| Markdown Twin Wrong Type | medium | usability | vendor profile: The /llms.txt file — markdown versions of pages |
Supporting documents: The /llms.txt file — markdown versions of pages Related guidance in The /llms.txt file — markdown versions of pages. Bad: the alternate link (found by its .md href) doesn't declare type="text/markdown", so agents scanning by MIME type won't recognise it as a Markdown twin. Fix: add type="text/markdown" to the <link rel="alternate">. | |||
| Markdown Twin Empty Href | medium | usability | vendor profile: The /llms.txt file — markdown versions of pages |
Supporting documents: The /llms.txt file — markdown versions of pages Related guidance in The /llms.txt file — markdown versions of pages. Bad: the Markdown alternate link has an empty (or absent) href, so it advertises a twin without saying where it is. Fix: point href at the Markdown resource, e.g. href="/page.md". | |||
Examples
Both run through the same checks as a live scan: the first passes, the second is flagged.
<link rel="alternate" type="text/markdown" href="https://example.com/content/correct.md" /><link rel="alternate" type="text/html" href="https://example.com/content/issues.md" />
<link rel="alternate" type="text/markdown" href="" />Specifications
| Document | Revision | Kind |
|---|---|---|
| The /llms.txt file — markdown versions of pages | Version 2, August 2026 | specification |
| specification.website — markdown source endpoints | Living document | guidance |
| Dualmark — content negotiation | Living document | guidance |
| Vercel: make your site readable by AI agents | Living document | guidance |
Last re-read against the published documents: .