hugo/docs/content/en/templates/data-templates.md

---
title: Data Templates
linktitle:
description: In addition to Hugo's built-in variables, you can specify your own custom data in templates or shortcodes that pull from both local and dynamic sources.
date: 2017-02-01
publishdate: 2017-02-01
lastmod: 2017-03-12
categories: [templates]
keywords: [data,dynamic,csv,json,toml,yaml]
menu:
  docs:
    parent: "templates"
    weight: 80
weight: 80
sections_weight: 80
draft: false
aliases: [/extras/datafiles/,/extras/datadrivencontent/,/doc/datafiles/]
toc: true
---

<!-- begin data files -->

Hugo supports loading data from YAML, JSON, and TOML files located in the `data` directory in the root of your Hugo project.

{{< youtube FyPgSuwIMWQ >}}

## The Data Folder

The `data` folder is where you can store additional data for Hugo to use when generating your site. Data files aren't used to generate standalone pages; rather, they're meant to be supplemental to content files. This feature can extend the content in case your front matter fields grow out of control. Or perhaps you want to show a larger dataset in a template (see example below). In both cases, it's a good idea to outsource the data in their own files.

These files must be YAML, JSON, or TOML files (using the `.yml`, `.yaml`, `.json`, or `.toml` extension). The data will be accessible as a `map` in the `.Site.Data` variable.

## Data Files in Themes

Data Files can also be used in [Hugo themes][themes] but note that theme data files follow the same logic as other template files in the [Hugo lookup order][lookup] (i.e., given two files with the same name and relative path, the file in the root project `data` directory will override the file in the `themes/<THEME>/data` directory).

Therefore, theme authors should take care to not include data files that could be easily overwritten by a user who decides to [customize a theme][customize]. For theme-specific data items that shouldn't be overridden, it can be wise to prefix the folder structure with a namespace; e.g. `mytheme/data/<THEME>/somekey/...`. To check if any such duplicate exists, run hugo with the `-v` flag.

The keys in the map created with data templates from data files will be a dot-chained set of `path`, `filename`, and `key` in file (if applicable).

This is best explained with an example:

## Example: Jaco Pastorius' Solo Discography

[Jaco Pastorius](https://en.wikipedia.org/wiki/Jaco_Pastorius_discography) was a great bass player, but his solo discography is short enough to use as an example. [John Patitucci](https://en.wikipedia.org/wiki/John_Patitucci) is another bass giant.

The example below is a bit contrived, but it illustrates the flexibility of data Files. This example uses TOML as its file format with the two following data files:

* `data/jazz/bass/jacopastorius.toml`
* `data/jazz/bass/johnpatitucci.toml`

`jacopastorius.toml` contains the content below. `johnpatitucci.toml` contains a similar list:

```
discography = [
"1974 – Modern American Music … Period! The Criteria Sessions",
"1974 – Jaco",
"1976 - Jaco Pastorius",
"1981 - Word of Mouth",
"1981 - The Birthday Concert (released in 1995)",
"1982 - Twins I & II (released in 1999)",
"1983 - Invitation",
"1986 - Broadway Blues (released in 1998)",
"1986 - Honestly Solo Live (released in 1990)",
"1986 - Live In Italy (released in 1991)",
"1986 - Heavy'n Jazz (released in 1992)",
"1991 - Live In New York City, Volumes 1-7.",
"1999 - Rare Collection (compilation)",
"2003 - Punk Jazz: The Jaco Pastorius Anthology (compilation)",
"2007 - The Essential Jaco Pastorius (compilation)"
]
```

The list of bass players can be accessed via `.Site.Data.jazz.bass`, a single bass player by adding the filename without the suffix, e.g. `.Site.Data.jazz.bass.jacopastorius`.

You can now render the list of recordings for all the bass players in a template:

```
{{ range $.Site.Data.jazz.bass }}
   {{ partial "artist.html" . }}
{{ end }}
```

And then in the `partials/artist.html`:

```
<ul>
{{ range .discography }}
  <li>{{ . }}</li>
{{ end }}
</ul>
```

Discover a new favorite bass player? Just add another `.toml` file in the same directory.

## Example: Accessing Named Values in a Data File

Assume you have the following data structure in your `User0123.[yml|toml|json]` data file located directly in `data/`:

{{< code-toggle file="User0123" >}}
Name: User0123
"Short Description": "He is a **jolly good** fellow."
Achievements:
  - "Can create a Key, Value list from Data File"
  - "Learns Hugo"
  - "Reads documentation"
{{</ code-toggle >}}

You can use the following code to render the `Short Description` in your layout::

```
<div>Short Description of {{.Site.Data.User0123.Name}}: <p>{{ index .Site.Data.User0123 "Short Description" | markdownify }}</p></div>
```

Note the use of the [`markdownify` template function][markdownify]. This will send the description through the Blackfriday Markdown rendering engine.

<!-- begin "Data-drive Content" page -->

## Data-Driven Content

In addition to the [data files](/extras/datafiles/) feature, Hugo also has a "data-driven content" feature, which lets you load any [JSON](https://www.json.org/) or [CSV](https://en.wikipedia.org/wiki/Comma-separated_values) file from nearly any resource.

Data-driven content currently consists of two functions, `getJSON` and `getCSV`, which are available in all template files.

## Implementation details

### Call the Functions with a URL

In your template, call the functions like this:

```
{{ $dataJ := getJSON "url" }}
{{ $dataC := getCSV "separator" "url" }}
```

If you use a prefix or postfix for the URL, the functions accept [variadic arguments][variadic]:

```
{{ $dataJ := getJSON "url prefix" "arg1" "arg2" "arg n" }}
{{ $dataC := getCSV  "separator" "url prefix" "arg1" "arg2" "arg n" }}
```

The separator for `getCSV` must be put in the first position and can only be one character long.

All passed arguments will be joined to the final URL:

```
{{ $urlPre := "https://api.github.com" }}
{{ $gistJ := getJSON $urlPre "/users/GITHUB_USERNAME/gists" }}
```

This will resolve internally to the following:

```
{{ $gistJ := getJSON "https://api.github.com/users/GITHUB_USERNAME/gists" }}
```

Finally, you can range over an array. This example will output the
first 5 gists for a GitHub user:

```
<ul>
  {{ $urlPre := "https://api.github.com" }}
  {{ $gistJ := getJSON $urlPre "/users/GITHUB_USERNAME/gists" }}
  {{ range first 5 $gistJ }}
    {{ if .public }}
      <li><a href="{{ .html_url }}" target="_blank">{{ .description }}</a></li>
    {{ end }}
  {{ end }}
</ul>
```

### Example for CSV files

For `getCSV`, the one-character-long separator must be placed in the first position followed by the URL. The following is an example of creating an HTML table in a [partial template][partials] from a published CSV:

{{< code file="layouts/partials/get-csv.html" >}}
  <table>
    <thead>
      <tr>
      <th>Name</th>
      <th>Position</th>
      <th>Salary</th>
      </tr>
    </thead>
    <tbody>
    {{ $url := "https://example.com/finance/employee-salaries.csv" }}
    {{ $sep := "," }}
    {{ range $i, $r := getCSV $sep $url }}
      <tr>
        <td>{{ index $r 0 }}</td>
        <td>{{ index $r 1 }}</td>
        <td>{{ index $r 2 }}</td>
      </tr>
    {{ end }}
    </tbody>
  </table>
{{< /code >}}

The expression `{{index $r number}}` must be used to output the nth-column from the current row.

### Cache URLs

Each downloaded URL will be cached in the default folder `$TMPDIR/hugo_cache/`. The variable `$TMPDIR` will be resolved to your system-dependent temporary directory.

With the command-line flag `--cacheDir`, you can specify any folder on your system as a caching directory.

You can also set `cacheDir` in the [main configuration file][config].

If you don't like caching at all, you can fully disable caching with the command line flag `--ignoreCache`.

### Authentication When Using REST URLs

Currently, you can only use those authentication methods that can be put into an URL. [OAuth][] and other authentication methods are not implemented.

## Load Local files

To load local files with `getJSON` and `getCSV`, the source files must reside within Hugo's working directory. The file extension does not matter, but the content does.

It applies the same output logic as above in [Call the Functions with a URL](#call-the-functions-with-a-url).

{{% note %}}
The local CSV files to be loaded using `getCSV` must be located **outside** of the `data` directory.
{{% /note %}}

## LiveReload with Data Files

There is no chance to trigger a [LiveReload][] when the content of a URL changes. However, when a *local* file changes (i.e., `data/*` and `themes/<THEME>/data/*`), a LiveReload will be triggered. Symlinks are not supported. Note too that because downloading of data takes a while, Hugo stops processing your Markdown files until the data download has completed.

{{% warning "URL Data and LiveReload" %}}
If you change any local file and the LiveReload is triggered, Hugo will read the data-driven (URL) content from the cache. If you have disabled the cache (i.e., by running the server with `hugo server --ignoreCache`), Hugo will re-download the content every time LiveReload triggers. This can create *huge* traffic. You may reach API limits quickly.
{{% /warning %}}

## Examples of Data-driven Content

- Photo gallery JSON powered: [https://github.com/pcdummy/hugo-lightslider-example](https://github.com/pcdummy/hugo-lightslider-example)
- GitHub Starred Repositories [in a post](https://github.com/SchumacherFM/blog-cs/blob/master/content%2Fposts%2Fgithub-starred.md) using data-driven content in a [custom short code](https://github.com/SchumacherFM/blog-cs/blob/master/layouts%2Fshortcodes%2FghStarred.html).

## Specs for Data Formats

* [TOML Spec][toml]
* [YAML Spec][yaml]
* [JSON Spec][json]
* [CSV Spec][csv]

[config]: /getting-started/configuration/
[csv]: https://tools.ietf.org/html/rfc4180
[customize]: /themes/customizing/
[json]: https://www.ecma-international.org/publications/files/ECMA-ST/ECMA-404.pdf "Specification for JSON, JavaScript Object Notation"
[LiveReload]: /getting-started/usage/#livereload
[lookup]: /templates/lookup-order/
[markdownify]: /functions/markdownify/
[OAuth]: https://en.wikipedia.org/wiki/OAuth
[partials]: /templates/partials/
[themes]: /themes/
[toml]: https://github.com/toml-lang/toml
[variadic]: https://en.wikipedia.org/wiki/Variadic_function
[vars]: /variables/
[yaml]: https://yaml.org/spec/