Agent Ready HTML

Fern: vendor profile

In short

Fern joined Postman on 2026-01-08 and keeps its own brand. Its docs sites are prebuilt static pages that ship llms.txt, .md copies and markdown for Accept: text/markdown. A missing .md address answered 200 with similar pages. The free plan allows 1,000 pages; custom React components need Enterprise.

At a glance

standards.txt fern

llms-txt               = supports
markdown-negotiation   = supports
markdown-twin          = supports
initial-html           = supports
real-404               = partial
vary-accept            = no statement

4 supports, 1 partial or announced, 1 no statement.

Fern Docs platform

Fern, now a Postman company, builds API docs sites that are prebuilt as static pages at the edge and ship llms.txt, .md copies, markdown on Accept: text/markdown, JSON-LD, sitemaps and an agent directive on every page.

Type
Docs platform
Operator, as the facts below state it
Postman
Headquarters
United States
Home page
buildwithfern.com, answered HTTP 200 on 2026-11-05
Last read
5 November 2026

What it does for this layer

  • Fern announced on 2026-01-08 that it has joined Postman, that the entire Fern team moved to Postman and that Fern keeps running as an independent product under its own brand. [primary source, 2026-01-08] source, read 5 November 2026.
  • Fern dates its founding to 2022, when it set out to help businesses ship better public APIs, and says both Fern Docs and its SDK generator are open source. [primary source] source, read 5 November 2026.
  • Fern generates meta tags, social previews, canonical URLs, JSON-LD structured data, clean slugs and llms.txt content for every indexable page with no configuration. [primary source] source, read 5 November 2026.
  • Fern's sitemap.xml gives each page a lastmod value that changes only when the content changes, so whitespace or capitalization edits do not bump it. [primary source] source, read 5 November 2026.
  • Fern serves a default robots.txt that allows all crawlers; a custom file set with the agents.robots-txt key in docs.yml is served verbatim with a Fern-managed block appended. [primary source] source, read 5 November 2026.
  • Fern's <llms-only> and <llms-ignore> tags split one page between readers and agents, so llms-only text reaches llms.txt and the .md copy but stays hidden in the rendered page. [primary source] source, read 5 November 2026.
  • Fern prepends a default directive to every page's agent markdown that points to the .md URLs and llms.txt; the page-directive key in docs.yml replaces it or turns it off. [primary source] source, read 5 November 2026.
  • Fern renders custom React components on the server so their output lands in the HTML, but custom components are an Enterprise plan feature. [primary source] source, read 5 November 2026.
  • Fern's self-hosting, an Enterprise feature, ships the docs site as the fernenterprise/fern-self-hosted Docker image, and offline AI chat was still in development. [primary source] source, read 5 November 2026.
  • Fern's post of 2026-10-26 says the old renderer sent each page twice, as HTML and as a data payload worth 72% to 75% of the HTML, and the new static pages are 2 to 4 times smaller. [primary source, 2026-10-26] source, read 5 November 2026.
  • Fern's changelog of 2026-10-08 turned on dynamic Open Graph images by default for sites with no site-wide og:image, switchable off with og:dynamic: false. [primary source, 2026-10-08] source, read 5 November 2026.
  • Fern's free Docs plan allows 10 team members, 1,000 pages, 250 AI credits and 2,000 page generations a month, with custom domain or subpath, Ask Fern and an MCP server. [primary source, 2026-11-05] source, read 5 November 2026.
  • A curl GET of a made-up .md URL under buildwithfern.com/learn/docs on 2026-11-05 returned HTTP 200 text/plain listing similar pages, while the HTML path returned 404. [observed, 2026-11-05] source, read 5 November 2026.
  • Served through Cloudflare, Fern's text/markdown response for the SEO overview page named Accept as its Vary value on 2026-11-05. [observed, 2026-11-05] source, read 5 November 2026.
  • The initial HTML of Fern's SEO overview page held a JSON-LD block typed TechArticle, BreadcrumbList and WebSite when fetched with curl on 2026-11-05. [observed, 2026-11-05] source, read 5 November 2026.

Products and plans

Plans and prices as the vendor's own pages showed them on the date read.
ProductWhat it isPriceAs ofSource
Fern Docs FreeHosted docs with guides, API references, changelogs, custom domain or subpath, Ask Fern, Fern Agent and an MCP server.Free
Free forever, $0 per month; 1,000 pages, 250 AI credits a month		2026-11-05source
Fern Docs EnterpriseAdds SSO, SCIM, RBAC, custom CSS, JavaScript and React components, multiple repos and self-hosting.Quote on request
Custom pricing		2026-11-05source

Standards

The six standards this site tracks; no statement means the pages read said nothing.
StandardStatusWhat the vendor's pages saySource
llms-txtsupportsFern's SEO overview lists llms.txt output among the defaults generated for indexable pages.source
markdown-negotiationsupportsFern's markdown access page documents content negotiation on the Accept: text/markdown header.source
markdown-twinsupportsEach page has .md and .mdx variants per the markdown access docs.source
initial-htmlsupportsEvery Fern Docs site is prebuilt as static pages, and custom React components are server-side rendered.source
real-404partialHTML paths return 404, but a made-up .md path returned 200 text/plain with similar pages on 2026-11-05.source
vary-acceptno statementNo statement on Vary found in the markdown access docs; Fern answered with vary: Accept on 2026-11-05.source

Checks on its own site

Readings of buildwithfern.com, the vendor's own website, which describe that site and not the product.
ReadingResultDate
Home page requestHTTP 200; H1 in the initial HTML: yes; 2,031 words; 4 JSON-LD blocks2026-11-05
Request with Accept: text/markdownHTTP 200, text/html, Vary: Accept-Encoding2026-11-05
/llms.txt at the host rootHTTP 200, text/plain, 44 KB, starts with an H12026-11-05
A made-up pathHTTP 4042026-11-05
Ora score, cached72, grade B2026-11-04
Cloudflare keyless scan27, L1 Basic Web Presence2026-11-05
Shared crawl rowoutside the ranked slice; home page HTTP 200; H1 in the HTML: yes; 1,400 words; JSON-LD types: Organization, WebSite; answers markdown: no; made-up path HTTP 404; llms.txt valid: yes2026-11-04

What it does not do

  • A custom robots.txt on Fern is never served alone, since Fern appends its own User-Agent: * group and a block for internal API routes.

Related pages on this site

Sources

  1. Fern: home page https://buildwithfern.com/, read 5 November 2026
  2. Fern blog: Fern has joined Postman https://buildwithfern.com/post/postman-acquires-fern, read 5 November 2026
  3. Overview of SEO & GEO | Fern Documentation https://buildwithfern.com/learn/docs/seo/overview, read 5 November 2026
  4. Custom robots.txt | Fern Documentation https://buildwithfern.com/learn/docs/seo/robots-txt, read 5 November 2026
  5. Customize LLM output | Fern Documentation https://buildwithfern.com/learn/docs/ai-features/customize-llm-output, read 5 November 2026
  6. Agent directives | Fern Documentation https://buildwithfern.com/learn/docs/ai-features/agent-directives, read 5 November 2026
  7. Custom React components | Fern Documentation https://buildwithfern.com/learn/docs/customization/custom-react-components, read 5 November 2026
  8. Self-hosted documentation | Fern Documentation https://buildwithfern.com/learn/docs/self-hosted/overview, read 5 November 2026
  9. Fern Docs sites are now static, and much faster | Fern https://buildwithfern.com/post/static-docs, read 5 November 2026
  10. Changelog | Fern Documentation https://buildwithfern.com/learn/docs/changelog, read 5 November 2026
  11. Pricing | Fern https://buildwithfern.com/pricing, read 5 November 2026
  12. Markdown access | Fern Documentation https://buildwithfern.com/learn/docs/ai-features/markdown, read 5 November 2026

Last reviewed 5 November 2026