Altdown
An open standard for making web content easier for AI agents to discover and read.
A site publishes a Markdown copy of each page's main content and announces it with one <link> element in the page's <head>. Agents read what the publisher says the page says, in a fraction of the tokens, instead of guessing from the HTML. An optional index lists every copy, so an agent can discover a whole site at once. Each copy is a plain static file, so a folder of files on any web host can conform.
Read the specification Read it as Markdown
Three parts
A site adopts Altdown with three parts. The first two are required. The third is optional.
| Part | What it is | Where it lives | Required |
|---|---|---|---|
| Markdown copy | One .md file per page, with front matter and the page's main content |
Next to the page, on the same origin | Yes |
| Link element | One <link rel="alternate" type="text/markdown"> per page |
In the page's <head> |
Yes |
| Site index | One JSON Feed 1.1 document that lists every copy | Anywhere on the origin, named in robots.txt |
No |
In the page's head
<link rel="alternate" type="text/markdown" href="/blog/static-sites/index.md">At the top of the copy
---
altdown: 1
canonical: https://example.com/blog/static-sites/
title: Why we went back to static sites
---