This output format is built with Bootstrap, using carefully crafted features to provide a clean reading experience whether you are on a phone, tablet, or desktop. To read more about this format, see:

  theme = bs4_book_theme(),
  repo = NULL,
  lib_dir = "libs",
  pandoc_args = NULL,
  extra_dependencies = NULL,
  template = "default",
  split_bib = FALSE

bs4_book_theme(primary = "#0068D9", version = 4, ...)



A named list or bslib::bs_theme() object. The default, bs4_book_theme(), resets the base font size to 1rem to make reading easier and uses a primary colour with greater contrast against the background.


Either link to repository where book is hosted, used to generate view source and edit buttons or a list with repository base link, default branch, subdir and icon (see "Specifying the repository" in

lib_dir, pandoc_args, extra_dependencies, split_bib, ...

Passed on to rmarkdown::html_document().


Pandoc template to use for rendering. Pass "default" to use the bookdown default template; pass a path to use a custom template. The default template should be sufficient for most use cases. For advanced user only, in case you want to develop a custom template, we highly recommend to start from the default template: Otherwise, some feature may not work anymore.


Primary colour: used for links and background of footer.


Passed to bslib::bs_theme(). This should not be changed as bs4_book() has been designed to work with Bootstrap version 4 for now.