Directory Structure

A basic Jekyll site usually looks something like this:

.
├── _config.yml
├── _data
|   └── members.yml
├── _drafts
|   ├── begin-with-the-crazy-ideas.md
|   └── on-simplicity-in-technology.md
├── _includes
|   ├── footer.html
|   └── header.html
├── _layouts
|   ├── default.html
|   └── post.html
├── _posts
|   ├── 2007-10-29-why-every-programmer-should-play-nethack.md
|   └── 2009-04-26-barcamp-boston-4-roundup.md
├── _sass
|   ├── _base.scss
|   └── _layout.scss
├── _site
├── .jekyll-metadata
└── index.html # can also be an 'index.md' with valid front matter

Directory structure of Jekyll sites using gem-based themes

Starting Jekyll 3.2, a new Jekyll project bootstrapped with jekyll new uses gem-based themes to define the look of the site. This results in a lighter default directory structure : _layouts, _includes and _sass are stored in the theme-gem, by default.

minima is the current default theme, and bundle show minima will show you where minima theme's files are stored on your computer.

An overview of what each of these does:

File / Directory	Description
`_config.yml`	Stores configuration data. Many of these options can be specified from the command line executable but it’s easier to specify them here so you don’t have to remember them.
`_drafts`	Drafts are unpublished posts. The format of these files is without a date: `title.MARKUP`. Learn how to work with drafts.
`_includes`	These are the partials that can be mixed and matched by your layouts and posts to facilitate reuse. The liquid tag `{% include file.ext %}` can be used to include the partial in `_includes/file.ext`.
`_layouts`	These are the templates that wrap posts. Layouts are chosen on a post-by-post basis in the front matter, which is described in the next section. The liquid tag `{{ content }}` is used to inject content into the web page.
`_posts`	Your dynamic content, so to speak. The naming convention of these files is important, and must follow the format: `YEAR-MONTH-DAY-title.MARKUP`. The permalinks can be customized for each post, but the date and markup language are determined solely by the file name.
`_data`	Well-formatted site data should be placed here. The Jekyll engine will autoload all data files (using either the `.yml`, `.yaml`, `.json`, `.csv` or `.tsv` formats and extensions) in this directory, and they will be accessible via `site.data`. If there's a file `members.yml` under the directory, then you can access contents of the file through `site.data.members`.
`_sass`	These are sass partials that can be imported into your `main.scss` which will then be processed into a single stylesheet `main.css` that defines the styles to be used by your site.
`_site`	This is where the generated site will be placed (by default) once Jekyll is done transforming it. It’s probably a good idea to add this to your `.gitignore` file.
`.jekyll-metadata`	This helps Jekyll keep track of which files have not been modified since the site was last built, and which files will need to be regenerated on the next build. This file will not be included in the generated site. It’s probably a good idea to add this to your `.gitignore` file.
`index.html` or `index.md` and other HTML, Markdown files	Provided that the file has a front matter section, it will be transformed by Jekyll. The same will happen for any `.html`, `.markdown`, `.md`, or `.textile` file in your site’s root directory or directories not listed above.
Other Files/Folders	Every other directory and file except for those listed above—such as `css` and `images` folders, `favicon.ico` files, and so forth—will be copied verbatim to the generated site. There are plenty of sites already using Jekyll if you’re curious to see how they’re laid out.