Layouts
Layouts are templates that wrap around your content. They allow you to have the source code for your template in one place so you don’t have to repeat things like your navigation and footer on every page.
Layouts live in the _layouts directory. The convention is to have a base
template called default.html and have other layouts inherit
from this as needed.
Layouts Directory
Jekyll looks for the _layouts directory either at the root of
your site's source or at the root of your theme.
While you can configure the directory name in which your layouts can reside by
setting the layouts_dir key in your config file, the directory
itself should be located at the root of your site's source directory.
Usage
The first step is to put the template source code in default.html. content
is a special variable, the value is the rendered content of the post or page
being wrapped.
<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>{{ page.title }}</title>
<link rel="stylesheet" href="/css/style.css">
</head>
<body>
<nav>
<a href="/">Home</a>
<a href="/blog/">Blog</a>
</nav>
<h1>{{ page.title }}</h1>
<section>
{{ content }}
</section>
<footer>
© to me
</footer>
</body>
</html>
You have full access to the front matter of the origin. In the
example above, page.title comes from the page front matter.
Next you need to specify what layout you’re using in your page’s front matter. You can also use front matter defaults to save you from having to set this on every page.
---
title: My First Page
layout: default
---
This is the content of my page
The rendered output of this page is:
<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>My First Page</title>
<link rel="stylesheet" href="/css/style.css">
</head>
<body>
<nav>
<a href="/">Home</a>
<a href="/blog/">Blog</a>
</nav>
<h1>My First Page</h1>
<section>
This is the content of my page
</section>
<footer>
© to me
</footer>
</body>
</html>
Inheritance
Layout inheritance is useful when you want to add something to an existing layout for a portion of documents on your site. A common example of this is blog posts, you might want a post to display the date and author but otherwise be identical to your base layout.
To achieve this you need to create another layout which specifies your original
layout in front matter. For example this layout will live at
_layouts/post.html:
---
layout: default
---
<p>{{ page.date }} - Written by {{ page.author }}</p>
{{ content }}
Now posts can use this layout while the rest of the pages use the default.
Variables
You can set front matter in layouts, the only difference is when you’re
using in Liquid, you need to use the layout variable instead of page. For
example:
---
city: San Francisco
---
<p>{{ layout.city }}</p>
{{ content }}