In your site source root, make a _plugins directory. Place your plugins here. Any file ending in *.rb inside this directory will be loaded before Jekyll generates your site.
# This will require each of these plugins automatically.
Now you need to install all plugins from your Bundler group by running single command bundle install.
GitHub Pages is powered by Jekyll. All Pages sites are generated using the --safe option to disable plugins (with the exception of some whitelisted plugins) for security reasons. Unfortunately, this means your plugins won't work if you're deploying to GitHub Pages.
You may use any of the aforementioned plugin options simultaneously in the same site if you so choose. Use of one does not restrict the use of the others.
Jekyll gives this particular group of gems in your Gemfile a different treatment. Any gem included in this group is loaded before Jekyll starts processing the rest of your source directory.
A gem included here will be activated even if its not explicitly listed under the plugins: key in your site's config file.
Gems included in the :jekyll-plugins group are activated regardless of the --safe mode setting. Be aware of what gems are included under this group!