Frequently asked questions

Building and publishing your project

Why does my project have status “failing”?

Projects have the status “failing” because something in the build process has failed. This can be because the project is not correctly configured, because the contents of the Git repository cannot be built, or in the most rare cases because a system that Read the Docs connects to is not working.

First, you should check out the Builds tab of your project. By clicking on the failing step, you will be able to see details that can lead to resolutions to your build error.

If the solution is not self-evident, you can use an important word or message from the error to search for a solution.

Why do I get import errors from libraries depending on C modules?


Another use case for this is when you have a module with a C extension.

This happens because the build system does not have the dependencies for building your project, such as C libraries needed by some Python packages (e.g. libevent or mysql). For libraries that cannot be installed via apt in the builder there is another way to successfully build the documentation despite missing dependencies.

With Sphinx you can use the built-in autodoc_mock_imports for mocking. If such libraries are installed via, you also will need to remove all the C-dependent libraries from your install_requires in the Read the Docs environment.

Where do I need to put my docs for Read the Docs to find it?

You can put your docs wherever your want on your repository. However, you will need to tell Read the Docs where your Sphinx’s (i.e. or MkDocs’ (i.e. mkdocs.yml) configuration file lives in order to build your documentation.

This is done by using sphinx.configuration or mkdocs.configuration config key in your Read the Docs configuration file. Read Configuration file overview to know more about this.

How can I avoid search results having a deprecated version of my docs?

If readers search something related to your docs in Google, it will probably return the most relevant version of your documentation. It may happen that this version is already deprecated and you want to stop Google indexing it as a result, and start suggesting the latest (or newer) one.

To accomplish this, you can add a robots.txt file to your documentation’s root so it ends up served at the root URL of your project (for example, We have documented how to set this up in robots.txt support.

How do I change the version slug of my project?

We don’t support allowing folks to change the slug for their versions. But you can rename the branch/tag to achieve this. If that isn’t enough, you can request the change sending an email to

What commit of Read the Docs is in production?

We deploy from the rel branch in our GitHub repository. You can see the latest commits that have been deployed by looking on GitHub:

We also keep an up-to-date changelog.

Additional features and configuration

How do I add additional software dependencies for my documentation?

For most Python dependencies, you can can specify a requirements file which details your dependencies. You can also set your project documentation to install your Python project itself as a dependency.

See also

Build process overview

An overview of the build process.

How to create reproducible builds

General information about adding dependencies and best-practices for maintaining them.

Build process customization

How to customize your builds, for example if you need to build with different tools from Sphinx or if you need to add additional packages for the Ubuntu-based builder.

Configuration file reference

Reference for the main configuration file, readthedocs.yaml


Reference for adding Debian packages with apt for the Ubuntu-based builders

Other FAQ entries

How do I change behavior when building with Read the Docs?

When Read the Docs builds your project, it sets the READTHEDOCS environment variable to the string 'True'. So within your Sphinx file, you can vary the behavior based on this. For example:

import os

on_rtd = os.environ.get("READTHEDOCS") == "True"
if on_rtd:
    html_theme = "default"
    html_theme = "nature"

The READTHEDOCS variable is also available in the Sphinx build environment, and will be set to True when building on Read the Docs:

{% endif %}

I want comments in my docs

Read the Docs doesn’t have explicit support for this. That said, a tool like Disqus (and the sphinxcontrib-disqus plugin) can be used for this purpose on Read the Docs.

Can I remove advertising from my documentation?

Yes. See Opting out of advertising.

How do I change my project slug (the URL your docs are served at)?

We don’t support allowing folks to change the slug for their project. You can update the name which is shown on the site, but not the actual URL that documentation is served.

The main reason for this is that all existing URLs to the content will break. You can delete and re-create the project with the proper name to get a new slug, but you really shouldn’t do this if you have existing inbound links, as it breaks the internet.

If that isn’t enough, you can request the change sending an email to

Big projects

How do I host multiple projects on one custom domain?

We support the concept of subprojects, which allows multiple projects to share a single domain. If you add a subproject to a project, that documentation will be served under the parent project’s subdomain or custom domain.

For example, Kombu is a subproject of Celery, so you can access it on the domain:

This also works the same for custom domains:

You can add subprojects in the project admin dashboard.

For details on custom domains, see our documentation on Custom domains.

How do I support multiple languages of documentation?

Read the Docs supports multiple languages. See the section on Localization and Internationalization.


I want to use the Read the Docs theme

To use the Read the Docs theme, you have to specify that in your Sphinx’s file.

Read the sphinx-rtd-theme documentation for instructions to enable it in your Sphinx project.

Image scaling doesn’t work in my documentation

Image scaling in docutils depends on Pillow. If you notice that image scaling is not working properly on your Sphinx project, you may need to add Pillow to your requirements to fix this issue. Read more about How to create reproducible builds to define your dependencies in a requirements.txt file.


Can I document a Python package that is not at the root of my repository?

Yes. The most convenient way to access a Python package for example via Sphinx’s autoapi in your documentation is to use the python.install.method: pip (python.install) configuration key.

This configuration will tell Read the Docs to install your package in the virtual environment used to build your documentation so your documentation tool can access to it.

Does Read the Docs work well with “legible” docstrings?

Yes. One criticism of Sphinx is that its annotated docstrings are too dense and difficult for humans to read. In response, many projects have adopted customized docstring styles that are simultaneously informative and legible. The NumPy and Google styles are two popular docstring formats. Fortunately, the default Read the Docs theme handles both formats just fine, provided your specifies an appropriate Sphinx extension that knows how to convert your customized docstrings. Two such extensions are numpydoc and napoleon. Only napoleon is able to handle both docstring formats. Its default output more closely matches the format of standard Sphinx annotations, and as a result, it tends to look a bit better with the default theme.


To use these extensions you need to specify the dependencies on your project by following this guide.

I need to install a package in a environment with pinned versions

If you’d like to pin your dependencies outside the package, you can add this line to your requirements or environment file (if you are using Conda).

In your requirements.txt file:

# path to the directory containing relative to the project root
-e .

In your Conda environment file (environment.yml):

# path to the directory containing relative to the environment file
-e ..

Other documentation frameworks

How can I deploy Jupyter Book projects on Read the Docs?

According to its own documentation,

Jupyter Book is an open source project for building beautiful, publication-quality books and documents from computational material.

Even though Jupyter Book leverages Sphinx “for almost everything that it does”, it purposedly hides Sphinx files from the user, and instead generates them on the fly from its declarative _config.yml. As a result, you need to follow some extra steps to make Jupyter Book work on Read the Docs.

As described in the official documentation, you can manually convert your Jupyter Book project to Sphinx with the following configuration:

         # Generate the Sphinx configuration for this Jupyter Book so it builds.
         - "jupyter-book config sphinx docs/"