Markdown URL fallback (.md)

A .md twin of each page lets an agent fetch Markdown by convention when the server does not negotiate.

Category: Content accessibility
Standard: Emerging; Off by default, turn on in settings

3%Top 100 adoption3 of 99 sites implement it 1/9OverviewStalledNo meaningful support, or vendors have said no.

Who supports it

No agent or browser has announced support yet.

27 others: no evidence yet. See every agent and browser

What it checks

The llms.txt proposal suggests publishing a Markdown copy of each page at the page’s URL with .md appended. The extension requests that twin for the page being scanned:

For a page such as /docs/setup, it requests /docs/setup.md.
For a directory URL such as /docs/, it requests /docs/index.html.md, then /docs/index.md.
For a URL that already ends in .md, there is nothing to probe.

A twin passes when it is served with a text/markdown content type.

Results

Status	When
Pass	A `.md` twin is served as `text/markdown`
Warn	A twin exists and looks like Markdown, but has a different content type
N/A	No `.md` twin was found

How to fix

Publish a Markdown version of each page at its URL plus .md, and at index.html.md for directory URLs. Serve them with the right content type:

Content-Type: text/markdown; charset=utf-8

Support by agent and browser

Announced means the vendor’s own docs or announcement say so. Published is the date on the vendor’s own page, where it has one. Checked is the last time our weekly research found that page still saying so.

No agent or browser has announced anything about this yet.

No evidence yet27

ChatGPT
Claude
Gemini
Perplexity
Copilot
Meta AI
ChatGPT Atlas
Comet
Dia
Gemini in Chrome
Edge Copilot Mode
Claude Code
Cursor
Codex
GitHub Copilot
Windsurf
CCBot
Applebot
Amazonbot
Bytespider
Cohere
Mistral
DuckAssist
Chrome
Edge
Firefox
Safari

Names and marks belong to their owners and are used only to identify products. None of these vendors is affiliated with Sitebulb. Spotted something out of date? Send a correction.

Adoption on the top 100 sites

3 of 99 measured sites implement it

Scanned 23 Oct 2026 with the Sitebulb Labs extension, against the Tranco list (tranco-56Z8N). 1 sites couldn’t be measured (bot challenge or timeout) and are left out of the share.

9 Oct 2026 4% → 23 Oct 2026 3%

Sites implementing it3

#2 cloudflare.com
#87 qq.com (with warnings)
#106 sentry.io

Overview

1/9

Stalled

No meaningful support, or vendors have said no.

How this rating is worked out1 of 9 points

Factor	Points	Why
Vendor support	0 / 3	0 vendors supporting, 0 partly or planned
Top-100 adoption	1 / 3	3% of measured sites
Spec maturity	0 / 3	Community proposal

8 or more points is Established, 5 to 7 is Gaining traction, 2 to 4 is Speculative and under 2 is Stalled. A feature is also Stalled when more vendors have said no than yes. Read the spec.

Community insights

No community insights for this feature yet.

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