Chapter 29 Dress it up!

In this section, we cover optional ways to make your bookdown site look ✨faaaabulous ✨. The features we cover below do not require knowing CSS nor HTML, and they’re all built-in things you can add to your bookdown now. There are a lot of different options here, and you certainly don’t have to implement all of them. Take an à la carte approach and pick the stuff you like!

We’ll need to use the three different bookdown YAML files to turn on these features. And sometimes, we don’t even need a YAML file and any old .Rmd doc will do. Here’s a cheatsheet of what file is in charge of what (including features we may have already covered earlier that we link to):


  • Add an edit link
  • Make the page downloadable as an .Rmd
  • Link to your GitHub in the toolbar, Part 1 (also need index.Rmd)
  • Add other sharing links
  • Header and footer of your TOC
  • Collapse the TOC by (sub)section
  • Code highlighting



  • Link to your GitHub in the toolbar, Part 2 (also need _output.yml)
  • Add a favicon
  • Book cover and description

Within any .Rmd

  • Group chapters into Parts
  • Add an appendix
  • Section (un)numbering

29.1 Before you begin

  1. Open up all three YAMLS and keep them open as tabs in RStudio. We’ll be bouncing in between these files:
    • _output.yml
    • _bookdown.yml
    • index.Rmd
  2. Remove output types we don’t need: from _output.yml. All of our cookbook content will only deal with the gitbook output from here on out. This means you can get rid of this part of the YAML in _output.yml:

We’ll fill out our YAML options one line at a time and show you what the growing YAMLs look like as we go.

29.2 Organizing

  • Collapse TOC by (sub)sections
  • Change the chapter name
  • Section (un)numbering
  • Group chapters into parts
  • Add an appendix

29.2.1 Collapse TOC by (sub)sections

We can control whether our TOC will show all sections or subsections by default. If you have very deep heading and section hierarchies, then you might want to play around with this option. You can read more about it in the bookdown documentation.

29.2.2 Change the chapter name

The chapter_name: option is what determines whether your level one headers will say “Chapter 1” or “Section 1” or “Module 1”—whatever prefix you’d like. In our example demo book, we’ll leave this as "Chapter ", but if you wanted to change it, you would do this:

  1. Open _bookdown.yml.
  2. Replace "Chapter " with your prefix of choice. Don’t forget the space after the name within the quotes.

29.2.3 Section (un)numbering

By default bookdown numbers all of your headings. If you don’t like this, then you have to un-number them manually. Within any .Rmd you can do this if you:

  • Add an {-} after each heading you want unnumbered.
  • If your section has an ID within brackets already, just add the - in front, for example:
## My Section {-#section-id}

We recommend keeping the numbering on for all of your chapters, except for the headings in your index.Rmd, which you should use as your preface or introduction.

Let’s remove numbering for the initial chapter of our minimal book, to make it clear it’s a preface:

  1. Open index.Rmd.
  2. Change the level one header to be # Prerequisites {-}
  3. Save and build your book.
  4. Notice that once you do, the numbering of all the following sections is automatically adjusted.

29.2.4 Group chapters into parts

If you have a bunch of chapters, it can be helpful to group some of them together (e.g., by semester, quarter, or content themes). You can create a book part within any .Rmd file by adding the following at the top of any .Rmd:

# (PART) My Part Title {-}

If you don’t want your part to be numbered with a Roman numeral, then you must instead write:

# (PART\*) My Part Title {-}

Let’s create two unnumbered parts for our demo book:

  1. Open the 01-intro.Rmd file.
  2. Add # (PART\*) First Semester {-} as the first line.
  3. Open 04-methods.Rmd file.
  4. Add # (PART\*) Second Semester {-} as the first line.

29.2.5 Appendix

Similar to “Parts”, you can create an appendix for your book with a header like:

# (APPENDIX) Appendix {-}

Any level one headers that come after this will be appendix chapters and will be “numbered” with letters. See more here.

Let’s create an appendix for our demo book by making a new .Rmd.

  1. In the IDE, create a fresh .Rmd by going to File > New File > R Markdown.
  2. Delete everything in this file.
  3. Add your appendix header at the top of the .Rmd: # (APPENDIX) Appendix {-}
  4. Optionally, some appendix chapters and content, like so:

    # (APPENDIX) Appendix {-} 
    # Appendix A
    Here is the first appendix chapter.
    # Appendix B
    Here is the second appendix chapter.
  5. Save this file in your project directory as appendix.Rmd. You can choose a different name.
  6. Open _bookdown.yml and add this new appendix .Rmd to the end of your list of .Rmds files.

29.3 Aesthetics

  • Header and footer of the TOC
  • Code highlighting

29.4 Edits and source code

  • Solicit edits via GitHub
  • See the .Rmd source code

Let’s add an edit icon the toolbar so that it’s easier for collaborators to give feedback and suggestions. When they click it, it will invite them to make changes on GitHub to the current book page.

  1. Open _output.yml.
  2. Create edit:, link:, and text: fields like you see below:

  3. Replace the parts of the URL that say “username” and “respository” with your own.
  4. Make sure the URL ends with /edit/master/%s.
  5. Add a message to the text: field. Something like "suggest an edit". This is what your user will see when they hover over the Edit link in the toolbar.

Save, build, and see that your edit icon works!

29.4.1 Share the source code

While we’re in _output.yml, we can add another field that will let your user see the source .Rmd code for the page. When your user clicks on the “download” icon, a new tab will open that shows them the .Rmd code used to generate the page they’re viewing (you have to have an edit: field for this to work). This isn’t technically a download, but still useful. Without specifying anything for this option, bookdown will look for other versions of your book (like PDFs or EPUB) to provide as a download. If you don’t want this, then you need to set download: no.

  1. Open _output.yml.
  2. After the download: option, replace "pdf", "epub" with "rmd". Since we removed the pdf_book and epub_book output, the “download” PDF and EPUB options wouldn’t have worked anyway.

29.5 Polishing and sharing

  • Sharing to Twitter, etc.
  • Directing to GitHub
  • Favicon
  • Book cover and description

29.5.1 Twitter and GitHub

When you turn sharing on, it’s easier for people to give your book a shoutout on twitter or find their way to your repo. This is good! We suggest using only these sharing icons and disabling the rest with all: no. Setting github: yes here is just one of the steps you need for the GitHub link to work. You also have to add your GitHub account and repo name to the index.Rmd YAML as we described above.

  1. Open _output.yml.
  2. Add a sharing: field.
  3. Set github: yes, facebook: no, twitter: yes, all: no.
    • Mind your indentation (remember, YAMLS are fussy!)
    • The Twitter icon is now set–but we’re only halfway there to get the GitHub icon to work.
  4. Open index.Rmd.
  5. Add the field github-repo: followed by your "username/repo".

Now, the GitHub icon will go to your book’s repo.

Next, we’ll move on to other polishing bits involved in sharing your book.

29.5.2 Add a favicon

You know the little tiny icon that gets placed in the corner of your browser tab? That’s a favicon! It’s also the icon that shows up when you’ve bookmarked a page. Let’s add one:

  1. Create a folder called images in your project directory. You don’t technically have to create this folder, but you will thank us later as you add more images to your book.
  2. Save the image you’d like to use (for best results it should be square) in images/.
    • Don’t have an image? Make one in less than a minute with text or an emoji:
      1. Go to free favicon generator and create a favicon
      2. Download and move the .ico file into your images/.
  3. Open index.Rmd.
  4. Add favicon: <"images/favicon.ico"> in the YAML, replacing the filepath in quotes with your own.

Note: In the example above, we can use ICO files (with the .ico extension) which are preferred because of better rendering across most browsers, but other images types like PNGs work too.

29.5.3 Book cover and description

Finally, we’ll change what happens what happens when we share preview links of our book.

  • cover-image: This lets you set an image that will act as your book’s cover. This will show up when we share a link of our book.
  • description: This is the short blurb that will also be part of the preview when your share the link of your book.

Let’s update our index.Rmd with the following:

  1. Update the description of our demo book to say “A work in progress.”

  2. Add a cover image by adding a path to our logo (or a url to any image–you can always try one of these if you need a placeholder).

  3. Now is also a good time to update your Title and Author fields if you haven’t already.

The formatting for url is really important, and weird:

  • You must use a forward slash \ before the colon to “escape” it.
  • The url must end with a back slash / in order for the cover-image to render.

Alright, we’ve done all we can here with bookdown’s built-in options. Time to checkout the options in Make it fancy if you’re still wanting more!