Jupyter Book uses [the Sphinx documentation engine](https://sphinx-doc.org) to build a rich document model from your source files.
Jupyter Book uses [the Sphinx documentation engine](https://www.sphinx-doc.org) to build a rich document model from your source files.
This also allows for some extra customization under the hood.
This chapter covers a few ways to customize Sphinx or to directly use it in building your book.
:::{caution}
Manually customizing Sphinx is considered **advanced usage** - it is highly recommended that you read the [Sphinx documentation](https://sphinx-doc.org).
Manually customizing Sphinx is considered **advanced usage** - it is highly recommended that you read the [Sphinx documentation](https://www.sphinx-doc.org).
