index.hbs is the handlebars template that is used to render the book. The markdown files are processed to html and then injected in that template.

If you want to change the layout or style of your book, chances are that you will have to modify this template a little bit. Here is what you need to know.


A lot of data is exposed to the handlebars template with the "context". In the handlebars template you can access this information by using


Here is a list of the properties that are exposed:

  • language Language of the book in the form en. To use in <html lang="{{ language }}"> for example. At the moment it is hardcoded.

  • title Title of the book, as specified in book.toml

  • chapter_title Title of the current chapter, as listed in

  • path Relative path to the original markdown file from the source directory

  • content This is the rendered markdown.

  • path_to_root This is a path containing exclusively ../'s that points to the root of the book from the current file. Since the original directory structure is maintained, it is useful to prepend relative links with this path_to_root.

  • chapters Is an array of dictionaries of the form

    {"section": "1.2.1", "name": "name of this chapter", "path": "dir/"}

    containing all the chapters of the book. It is used for example to construct the table of contents (sidebar).

Handlebars Helpers

In addition to the properties you can access, there are some handlebars helpers at your disposal.

  1. toc

    The toc helper is used like this


    and outputs something that looks like this, depending on the structure of your book

    <ul class="chapter">
        <li><a href="link/to/file.html">Some chapter</a></li>
            <ul class="section">
                <li><a href="link/to/other_file.html">Some other Chapter</a></li>

    If you would like to make a toc with another structure, you have access to the chapters property containing all the data. The only limitation at the moment is that you would have to do it with JavaScript instead of with a handlebars helper.

    var chapters = {{chapters}};
    // Processing here
  2. previous / next

    The previous and next helpers expose a link and name property to the previous and next chapters.

    They are used like this

        <a href="{{link}}" class="nav-chapters previous">
            <i class="fa fa-angle-left"></i>

    The inner html will only be rendered if the previous / next chapter exists. Of course the inner html can be changed to your liking.

If you would like me to expose other properties or helpers, please create a new issue and I will consider it.