Agent Ready HTML

Fern: what an agent reads

In short

Fern does not give individual pages their own llms.txt. Fern totals 14 of 16 on the eight numeric keys, from cited documentation read 4 November 2026. It also does not serve custom llms.txt files for non-default locales. Fern: Fern serves llms.txt at the root and for every navigation node: sections, products, versions, tabs, API references and changelogs.

rubric.txt fern

initial_html_by_default  = 2
real_status_codes        = 2
llms_txt_generation      = 2
llms_txt_linking         = 2
markdown_negotiation     = 2
jsonld_output            = 0
openapi_exposure         = 2
fenced_code              = 2
total                    = 14 of 16

Read 2026-11-04. Documentation, not a test build.

Fern Docs platform, Fern

API docs platform that generates llms.txt per navigation node, serves .md and .mdx twins and Accept: text/markdown, and returns agent-oriented 404s.

Work left to the developer: Low: write frontmatter descriptions; use llms-only and llms-ignore controls where needed.

The nine scores

KeyScoreEvidenceSource
Content in the initial HTML2, on by defaultSites are prebuilt as static pages since 2026-10-30. Not test-built: publishing docs needs a Fern account. Score from the documentation page cited, read 2026-11-04.buildwithfern.com/learn/docs/changelog, 2026-11-04
Real status codes2, on by defaultMissing .md URLs return agent 404 responses with suggestions. Not test-built: publishing docs needs a Fern account. Score from the documentation page cited, read 2026-11-04.buildwithfern.com/learn/docs/changelog, 2026-11-04
llms.txt generation2, on by defaultAutomatic at root and per navigation node. Not test-built: publishing docs needs a Fern account. Score from the documentation page cited, read 2026-11-04.buildwithfern.com/learn/docs/ai-features/llms-txt, 2026-11-04
llms.txt linking2, on by defaultA per-page directive prepended to markdown points agents to .md URLs and llms.txt. Not test-built: publishing docs needs a Fern account. Score from the documentation page cited, read 2026-11-04.buildwithfern.com/learn/docs/ai-features/markdown, 2026-11-04
Markdown on request2, on by defaultAccept: text/markdown documented. Not test-built: publishing docs needs a Fern account. Score from the documentation page cited, read 2026-11-04.buildwithfern.com/learn/docs/ai-features/markdown, 2026-11-04
JSON-LD output0, not offeredNot documented on the pages read. Not test-built: publishing docs needs a Fern account. Score from the documentation page cited, read 2026-11-04.buildwithfern.com/learn/docs/ai-features/markdown, 2026-11-04
OpenAPI exposure2, on by defaultllms.txt links the standalone OpenAPI spec. Not test-built: publishing docs needs a Fern account. Score from the documentation page cited, read 2026-11-04.buildwithfern.com/learn/docs/ai-features/llms-txt, 2026-11-04
Fenced, tagged code2, on by defaultMarkdown output keeps code; SDK examples can be filtered by language. Not test-built: publishing docs needs a Fern account. Score from the documentation page cited, read 2026-11-04.buildwithfern.com/learn/docs/changelog, 2026-11-04
Work left to the developerLow: write frontmatter descriptions; use llms-only and llms-ignore controls where needed. Descriptions come from frontmatter. Not test-built: publishing docs needs a Fern account. Score from the documentation page cited, read 2026-11-04.buildwithfern.com/learn/docs/ai-features/llms-txt, 2026-11-04

Test build

Not test-built: the scores above come from the documentation pages cited in each row, read 4 November 2026, because the platform needs an account or a paid plan. The reason is in each evidence cell.

What the documentation says

Each statement below carries its source and the date read. Statements a vendor makes about itself are labelled as vendor claims.

  • Fern generates and maintains llms.txt automatically and links the OpenAPI spec in it for sites with API endpoints, and the AsyncAPI spec for WebSocket channels. [primary source] source, read 4 November 2026.
  • Fern serves llms.txt at the root and for every navigation node: sections, products, versions, tabs, API references and changelogs. [primary source] source, read 4 November 2026.
  • A request for /<page>/llms.txt returns a 301 to the page markdown at /<page>.md. [primary source] source, read 4 November 2026.
  • Agents can fetch markdown by appending .md or .mdx or by sending Accept: text/markdown; Fern says this cuts token use by more than 90 percent against HTML. [vendor claim] source, read 4 November 2026.
  • API reference endpoint pages render as markdown with Request, Response and Authentication sections. [primary source] source, read 4 November 2026.
  • Changelog of 2026-09-18: llms.txt accepts lang=php and excludeChangelog=true, and agent 404 responses suggest up to five similar pages. [primary source, 2026-09-18] source, read 4 November 2026.
  • Changelog of 2026-10-30: Fern Docs sites are now prebuilt as static pages served from the edge, and custom domains pointing to Vercel must move to cname.ferndocs.com by 2026-12-01. [primary source, 2026-10-30] source, read 4 November 2026.

What it does not do

  • Does not give individual pages their own llms.txt.
  • Does not serve custom llms.txt files for non-default locales.

Compare and replace

Sources

  1. Fern docs: llms.txt https://buildwithfern.com/learn/docs/ai-features/llms-txt, read 4 November 2026
  2. Fern docs: Markdown access https://buildwithfern.com/learn/docs/ai-features/markdown, read 4 November 2026
  3. Fern changelog https://buildwithfern.com/learn/docs/changelog, read 4 November 2026
  4. buildwithfern.com https://buildwithfern.com/, read 4 November 2026

Last reviewed 4 November 2026