Quick statistics about documentation hosted on Read the Docs

Many open source projects host their online documentation with Read The Docs. Since I’m currently developing a tool for Read The Docs users, I recently took a look at the types of projects that are hosted there.

The data in this post is derived from the list of projects available in the public Read The Docs API, and has its limitations. In particular, spam, inactive, or abandoned projects are not filtered.

Totals

This data is current as of May 20, 2018. At that time, there were 90,129 total projects on readthedocs.io.

Starting out, I had assumed that the majority of projects had all four of these attributes:

  • Hosted in Git
  • Programmed in Python
  • Documented in English
  • Documentation generated with Sphinx

As it turned out, this particular combination is only used on 35.8% (32,218) of projects, so let’s take a look at how each of these vary.

Programming languages

The two main conclusions I drew by looking at the programming languages are:

  • Python is the largest developer community that is using the Read the Docs platform
  • A lot of projects are hosting documentation that is not tagged with a programming language
# % Projects Programming language
1 39.92% 35978 Not code (“just words”)
2 39.27% 35391 Python
3 9.27% 8354 (No language listed)
4 2.83% 2551 Javascript
5 2.29% 2060 PHP
6 1.15% 1040 C++
7 1.13% 1018 Java
8 0.85% 769 Other
9 0.77% 690 C#
10 0.71% 640 C
11 0.42% 380 CSS
12 0.34% 304 Go
13 0.31% 283 Ruby
14 0.31% 277 Julia
15 0.11% 96 Perl
16 0.06% 55 Objective C
17 0.06% 54 R
18 0.04% 36 TypeScript
19 0.03% 31 Scala
20 0.03% 30 Haskell
21 0.03% 29 Lua
22 0.02% 22 Swift
23 0.02% 15 CoffeeScript
24 0.02% 14 Visual Basic
25 0.01% 12 Groovy

Documentation languages

You might have guessed that English dominates in software documentation, but here is the data:

# % Projects Language
1 93.1% 83888 English (en)
2 2.4% 2178 Indonesian (id)
3 1.4% 1287 Chinese (zh, zh_TW, zh_CN)
4 0.5% 456 Russian (ru)
5 0.5% 425 Spanish (es)
6 0.5% 412 French (fr)
7 0.3% 254 Portuguese (pt)
8 0.3% 233 German (de)
9 0.2% 209 Italian (it)
10 0.2% 208 Japanese (jp)
0.6% 579 All other languages

In total, documentation on Read the Docs has been published in 54 languages. The “All other languages” item here represents 44 other languages.

Documentation build tool

The majority are using the Sphinx documentation generator. The table here counts sphinx, sphinx_htmldir and sphinx_singlehtml together.

# % Projects Language
1 92.5% 83364 Sphinx
2 6.9% 6229 MkDocs
3 0.6% 536 Auto-select

Version control

Git is the version control system used for the vast majority of projects.

# % Projects Version control
1 96.5% 86988 Git
2 2.1% 1879 Mercurial
3 0.9% 816 SVN
4 0.5% 446 Bazaar

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