Shared data

In addition to the variables defined in the pages and layouts, you can store data accessible by some or all pages. Shared data must be saved in the _data directory or _data.* files with extensions like .json, .yaml, .js or .ts.

The formats .json and .yaml are useful for static data. .js and .ts fit better for dynamic data (for example, data fetched from an API or a database):

{
  "people": [
    {
      "name": "Oscar Otero",
      "color": "black"
    },
    {
      "name": "Laura Rubio",
      "color": "blue"
    }
  ]
}

people:
  - name: Oscar Otero
    color: black

  - name: Laura Rubio
    color: blue

import { db } from "./database.ts";

const people = db.query("select name, color from people");

export { people };

The _data.* files

Any file named as _data.* is loaded and its content is accessible by all pages in the same directory or subdirectory.

├── _data.yaml      # Data shared with all pages
├── index.md
└── documentation
    └── _data.json  # Shared with pages in this directory and subdirectories
    └── doc1.md
    └── doc2.md
    └── examples
        └── _data.json  # Shared with pages in this directory and subdirectories
        └── example1.md
        └── example2.md

As you can see, the shared data is propagated in a cascade following the directory structure. A typical use case is to store those variables that are common to all pages in the same directory so you don't have to repeat it for every page.

The _data directories

_data directories are similar to _data files, but instead of using only one file, the data is stored in several files inside that directory. The basename of each file determines the variable name used to access the data. Let's see an example:

└── _data
    └── users.json
    └── documents
        └── one.js
        └── two.js
        └── three.js

In this example, the data stored in the file _data/users.json can be accessed via users variable and documents via documents.one, documents.two and documents.three. To use this data in your pages:

<h2>Documents</h2>

<ul>
{{ for doc of documents }}
  <li>
    {{ doc.title }}
  </li>
{{ /for }}
</ul>

export default function ({ documents }) {
  return (
    <>
      <h2>Documents</h2>

      <ul>
        {documents.map((doc) => <li>{doc.title}</li>)}
      </ul>
    </>
  );
}

Like _data.* files, you can have _data directories in different locations so they are shared only with all pages in the same directory or subdirectories.