Bunto has an extensive theme system that allows you to leverage community-maintained templates and styles to customize your site’s presentation. Bunto themes package up layouts, includes, and stylesheets in a way that can be overridden by your site’s content.

Understanding gem-based themes

When you create a new Bunto site (by running the bunto new <PATH> command), Bunto installs a site that uses a gem-based theme called Minima.

With gem-based themes, some of the site’s directories (such as the assets, _layouts, _includes, and _sass directories) are stored in the theme’s gem, hidden from your immediate view. Yet all of the necessary directories will be read and processed during Bunto’s build process.

In the case of Minima, you see only the following files in your Bunto site directory:

├── Gemfile
├── Gemfile.lock
├── _config.yml
├── _posts
│   └── 2016-12-04-welcome-to-bunto.markdown

The Gemfile and Gemfile.lock files are used by Bundler to keep track of the required gems and gem versions you need to build your Bunto site.

Gem-based themes make it easy for theme developers to make updates available to anyone who has the theme gem. When there’s an update, theme developers push the update to RubyGems.

If you have the theme gem, you can (if you desire) run bundle update to update all gems in your project. Or you can run bundle update <THEME>, replacing <THEME> with the theme name, such as minima, to just update the theme gem. Any new files or updates the theme developer has made (such as to stylesheets or includes) will be pulled into your project automatically.

The goal of gem-based themes is to allow you to get all the benefits of a robust, continually updated theme without having all the theme’s files getting in your way and over-complicating what might be your primary focus: creating content.

Overriding theme defaults

Bunto themes set default layouts, includes, and stylesheets. However, you can override any of the theme defaults with your own site content.

For example, if your selected theme has a page layout, you can override the theme’s layout by creating your own page layout in the _layouts directory (that is, _layouts/page.html).

Bunto will look first to your site’s content before looking to the theme’s defaults for any requested file in the following folders:

  • /assets
  • /_layouts
  • /_includes
  • /_sass

Refer to your selected theme’s documentation and source repository for more information on what files you can override.

To locate theme’s files on your computer:

  1. Run bundle show followed by the name of the theme’s gem, e.g., bundle show minima for default Bunto’s theme.

    This returns the location of the gem-based theme files. For example, Minima theme’s files are located in /usr/local/lib/ruby/gems/2.3.0/gems/minima-2.1.0 on macOS.

  2. Open the theme’s directory in Finder or Explorer:

    # On MacOS
    open $(bundle show minima)
    # On Windows
    explorer /usr/local/lib/ruby/gems/2.3.0/gems/minima-2.1.0

    A Finder or Explorer window opens showing the theme’s files and directories. The Minima theme gem contains these files:

     ├── LICENSE.txt
     ├── _includes
     │   ├── disqus_comments.html
     │   ├── footer.html
     │   ├── google-analytics.html
     │   ├── head.html
     │   ├── header.html
     │   ├── icon-github.html
     │   ├── icon-github.svg
     │   ├── icon-twitter.html
     │   └── icon-twitter.svg
     ├── _layouts
     │   ├── default.html
     │   ├── home.html
     │   ├── page.html
     │   └── post.html
     ├── _sass
     │   ├── minima
     │   │   ├── _base.scss
     │   │   ├── _layout.scss
     │   │   └── _syntax-highlighting.scss
     │   └── minima.scss
     └── assets
         └── main.scss

    With a clear understanding of the theme’s files, you can now override any theme file by creating a similarly named file in your Bunto site directory.

    Let’s say you want to override Minima’s footer. In your Bunto site, create an _includes folder and add a file in it called footer.html. Bunto will now use your site’s footer.html file instead of the footer.html file from the Minima theme gem.

Converting gem-based themes to regular themes

Suppose you want to get rid of the gem-based theme and convert it to a regular theme, where all files are present in your Bunto site directory, with nothing stored in the theme gem.

To do this, copy the files from the theme gem’s directory into your Bunto site directory. (For example, copy them to /myblog if you created your Bunto site at /myblog. See the previous section for details.)

Then remove references to the theme gem in Gemfile and configuration. For example, to remove minima:

  • Open Gemfile and remove gem "minima", "~> 2.0".
  • Open _config.yml and remove theme: minima.

Now bundle update will no longer get updates for the theme gem.

Installing a gem-based theme

The bunto new <PATH> command isn’t the only way to create a new Bunto site with a gem-based theme. You can also find gem-based themes online and incorporate them into your Bunto project.

For example, search for bunto theme on RubyGems to find other gem-based themes. (Note that not all themes are using bunto-theme as a convention in the theme name.)

To install a gem-based theme:

  1. Add the theme to your site’s Gemfile:

    gem "bunto-theme-awesome"
  2. Install the theme:

    bundle install
  3. Add the following to your site’s _config.yml to activate the theme:

    theme: bunto-theme-awesome
  4. Build your site:

    bundle exec bunto serve

You can have multiple themes listed in your site’s Gemfile, but only one theme can be selected in your site’s _config.yml. {: .note .info }

If you’re publishing your Bunto site on GitHub Pages, note that GitHub Pages supports only some gem-based themes. See Supported Themes in GitHub’s documentation to see which themes are supported.

Creating a gem-based theme

If you’re a Bunto theme developer (rather than just a consumer of themes), you can package up your theme in RubyGems and allow users to install it through Bundler.

If you’re unfamiliar with creating Ruby gems, don’t worry. Bunto will help you scaffold a new theme with the new-theme command. Run bunto new-theme with the theme name as an argument.

Here is an example:

bunto new-theme bunto-theme-awesome
    create /path/to/bunto-theme-awesome/_layouts
    create /path/to/bunto-theme-awesome/_includes
    create /path/to/bunto-theme-awesome/_sass
    create /path/to/bunto-theme-awesome/_layouts/page.html
    create /path/to/bunto-theme-awesome/_layouts/post.html
    create /path/to/bunto-theme-awesome/_layouts/default.html
    create /path/to/bunto-theme-awesome/Gemfile
    create /path/to/bunto-theme-awesome/bunto-theme-awesome.gemspec
    create /path/to/bunto-theme-awesome/
    create /path/to/bunto-theme-awesome/LICENSE.txt
    initialize /path/to/bunto-theme-awesome/.git
    create /path/to/bunto-theme-awesome/.gitignore
Your new Bunto theme, bunto-theme-awesome, is ready for you in /path/to/bunto-theme-awesome!
For help getting started, read /path/to/bunto-theme-awesome/

Add your template files in the corresponding folders. Then complete the .gemspec and the README files according to your needs.

Layouts and includes

Theme layouts and includes work just like they work in any Bunto site. Place layouts in your theme’s /_layouts folder, and place includes in your themes /_includes folder.

For example, if your theme has a /_layouts/page.html file, and a page has layout: page in its YAML front matter, Bunto will first look to the site’s _layouts folder for the page layout, and if none exists, will use your theme’s page layout.


Any file in /assets will be copied over to the user’s site upon build unless they have a file with the same relative path. You can ship any kind of asset here: SCSS, an image, a webfont, etc. These files behave like pages and static files in Bunto:

  • If the file has YAML front matter at the top, it will be rendered.
  • If the file does not have YAML front matter, it will simply be copied over into the resulting site.

This allows theme creators to ship a default /assets/styles.scss file which their layouts can depend on as /assets/styles.css.

All files in /assets will be output into the compiled site in the /assets folder just as you’d expect from using Bunto on your sites.


Your theme’s stylesheets should be placed in your theme’s _sass folder, again, just as you would when authoring a Bunto site.

├── bunto-theme-awesome.scss

Your theme’s styles can be included in the user’s stylesheet using the @import directive.

@import "{{ site.theme }}";

Documenting your theme

Your theme should include a / file, which explains how site authors can install and use your theme. What layouts are included? What includes? Do they need to add anything special to their site’s configuration file?

Adding a screenshot

Themes are visual. Show users what your theme looks like by including a screenshot as /screenshot.png within your theme’s repository where it can be retrieved programatically. You can also include this screenshot within your theme’s documentation.

Previewing your theme

To preview your theme as you’re authoring it, it may be helpful to add dummy content in, for example, /index.html and /page.html files. This will allow you to use the bunto build and bunto serve commands to preview your theme, just as you’d preview a Bunto site.

If you do preview your theme locally, be sure to add /_site to your theme’s .gitignore file to prevent the compiled site from also being included when you distribute your theme. {: .info .note}

Publishing your theme

Themes are published via You will need a RubyGems account, which you can create for free.

  1. First, package your theme, by running the following command, replacing bunto-theme-awesome with the name of your theme:

    gem build bunto-theme-awesome.gemspec
  2. Next, push your packaged theme up to the RubyGems service, by running the following command, again replacing bunto-theme-awesome with the name of your theme:

    gem push bunto-theme-awesome-*.gem
  3. To release a new version of your theme, update the version number in the gemspec file, ( bunto-theme-awesome.gemspec in this example ), and then repeat Steps 1 & 2 above. We recommend that you follow Semantic Versioning while bumping your theme-version.