Sphinx: vendor profile

In short

Sphinx writes a static HTML file per page and keeps page sources under _sources/, but its core has no Markdown builder, and a 404.html, sitemap.xml or llms.txt each need an extension. Sphinx's own site answers Accept: text/markdown through its host, Read the Docs. Sphinx 9.2.0 came out on 2026-10-20 under a BSD licence.

At a glance

standards.txt sphinx

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

1 supports, 3 partial or announced, 2 no statement.

Sphinx Framework

Python documentation generator whose html builders write a static HTML file per page and copy page sources into _sources/; llms.txt, 404 pages and sitemaps come from third-party extensions.

Type: Framework
Operator, as the facts below state it: Sphinx team (sphinx-doc)
Home page: www.sphinx-doc.org, answered HTTP 200 on 2026-11-05
Last read: 5 November 2026

What it does for this layer

Sphinx's standard html builder writes a directory of HTML files with style sheets and, optionally, the reStructuredText sources. [primary source] source, read 5 November 2026.
Sphinx's dirhtml builder writes each page as <name>/index.html, so links read like markup/rest/ without the file name. [primary source] source, read 5 November 2026.
Sphinx's built-in text builder writes one plain text file per reStructuredText file with much of the markup stripped; Sphinx core lists no Markdown builder. [primary source] source, read 5 November 2026.
html_copy_source defaults to True, so Sphinx copies each page's source into _sources/ with a .txt suffix, a plain source twin rather than rendered Markdown. [primary source] source, read 5 November 2026.
Sphinx's html_baseurl, empty by default and added in 1.8, sets the documentation root used for the canonical link relation. [primary source] source, read 5 November 2026.
Sphinx 9.2.0, released on 2026-10-20, dropped Python 3.12 and added support for Docutils 0.23. [primary source, 2026-10-20] source, read 5 November 2026.
Sphinx lists HTML, LaTeX for PDF, ePub and Texinfo among its output formats, with authoring in reStructuredText or MyST Markdown. [primary source] source, read 5 November 2026.
The community extension sphinx-llms-txt writes llms.txt in Markdown and a combined llms-full.txt in reStructuredText during a normal Sphinx build once added to conf.py. [secondary source] source, read 5 November 2026.
The sphinx-llms-txt docs point readers to sphinx-llm from NVIDIA for stronger default output without configuration. [secondary source] source, read 5 November 2026.
Sphinx makes no 404 page of its own; Read the Docs' sphinx-notfound-page extension builds one whose CSS, JS and image links still resolve on deep URLs. [secondary source] source, read 5 November 2026.
Sitemaps for Sphinx come from the third-party sphinx-sitemap extension, which writes sitemaps.org files across versions and languages. [secondary source] source, read 5 November 2026.
www.sphinx-doc.org, built by Sphinx and hosted on Read the Docs, answered Accept: text/markdown on the quickstart page with text/markdown and Vary: Accept-Encoding, accept on 2026-11-05; x-rtd headers show Read the Docs produced that variant. [observed] source, read 5 November 2026.
The quickstart source copy at /en/master/_sources/usage/quickstart.rst.txt on www.sphinx-doc.org answered 200 text/plain on 2026-11-05, while /llms.txt on the same host was a 404. [observed] source, read 5 November 2026.
Sphinx code is licensed under the two-clause BSD licence, copyright 2007-2026 the Sphinx team. [primary source] source, read 5 November 2026.

Products and plans

Plans and prices as the vendor's own pages showed them on the date read.
Product	What it is	Price	As of	Source
Sphinx	Python documentation generator with HTML, LaTeX, ePub and text builders.	Free, open source BSD 2-clause licence, free; 9.2.0 on 2026-10-20	2026-11-05	source

Standards

The six standards this site tracks; no statement means the pages read said nothing.
Standard	Status	What the vendor's pages say	Source
llms-txt	partial	Only through the third-party sphinx-llms-txt extension (or NVIDIA's sphinx-llm); Sphinx itself writes no llms.txt.	source
markdown-negotiation	no statement	No statement found in the Sphinx builders or configuration pages; the Markdown answer seen on www.sphinx-doc.org comes from Read the Docs hosting.	none
markdown-twin	partial	html_copy_source puts each page's source under _sources/ as .txt, which is Markdown only when the project is written in MyST.	source
initial-html	supports	The standard html builder outputs a directory of HTML files.	source
real-404	partial	Sphinx creates no 404 page by default; the sphinx-notfound-page extension adds one, and the status code depends on the host.	source
vary-accept	no statement	No statement found in the Sphinx builders, configuration or changelog pages; Sphinx outputs files and sets no headers.	none

Checks on its own site

Readings of sphinx-doc.org, the vendor's own website, which describe that site and not the product.
Reading	Result	Date
Home page request	HTTP 200; H1 in the initial HTML: yes; 777 words; 0 JSON-LD blocks	2026-11-05
Request with Accept: text/markdown	HTTP 200, text/markdown, Vary: Accept-Encoding, accept	2026-11-05
/llms.txt at the host root	HTTP 404, text/html, 2.3 KB	2026-11-05
A made-up path	HTTP 404	2026-11-05
Ora score, cached	Not available: GET /api/score returned 404 DOMAIN_NOT_SCANNED	2026-11-05
Cloudflare keyless scan	27, L1 Basic Web Presence	2026-11-05
Shared crawl row	Tranco rank 8,556; home page HTTP 200; H1 in the HTML: yes; 780 words; JSON-LD types: none; answers markdown: yes; made-up path HTTP 404; llms.txt valid: no	2026-11-04

What it does not do

Sphinx does not write a 404.html, a sitemap.xml or an llms.txt without extensions such as sphinx-notfound-page, sphinx-sitemap and sphinx-llms-txt.

Related pages on this site

Sources

Sphinx: home page https://www.sphinx-doc.org/, read 5 November 2026
Builders: Sphinx documentation https://www.sphinx-doc.org/en/master/usage/builders/index.html, read 5 November 2026
Configuration: Sphinx documentation https://www.sphinx-doc.org/en/master/usage/configuration.html, read 5 November 2026
Changelog: Sphinx documentation https://www.sphinx-doc.org/en/master/changes/index.html, read 5 November 2026
Sphinx: Sphinx documentation https://www.sphinx-doc.org/en/master/, read 5 November 2026
sphinx-llms-txt documentation https://sphinx-llms-txt.readthedocs.io/en/latest/, read 5 November 2026
sphinx-notfound-page documentation https://sphinx-notfound-page.readthedocs.io/en/latest/, read 5 November 2026
sphinx-sitemap documentation https://sphinx-sitemap.readthedocs.io/en/latest/, read 5 November 2026
License for Sphinx (LICENSE.rst) https://raw.githubusercontent.com/sphinx-doc/sphinx/master/LICENSE.rst, read 5 November 2026

Last reviewed 5 November 2026