path: root/content/en/templates/data-templates.md

---
title: Data templates
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.
categories: [templates]
keywords: [data,dynamic,csv,json,toml,yaml,xml]
menu:
  docs:
    parent: templates
    weight: 150
weight: 150
aliases: [/extras/datafiles/,/extras/datadrivencontent/,/doc/datafiles/]
toc: true
---

<!-- begin data files -->

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

{{< youtube FyPgSuwIMWQ >}}

## The data folder

The `data` folder should store additional data for Hugo to use when generating your site.

Data files are not for generating standalone pages. They should supplement content files by:

- extending the content when the front matter fields grow out of control, or
- showing a larger dataset in a template (see the example below).

In both cases, it's a good idea to outsource the data in their (own) files.

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

To access the data using the `site.Data.filename` notation, the file name must begin with an underscore or a Unicode letter, followed by zero or more underscores, Unicode letters, or Unicode digits. For example:

- `123.json` - Invalid
- `x123.json` - Valid
- `_123.json` - Valid

To access the data using the [`index`](/functions/collections/indexfunction) function, the file name is irrelevant. For example:

Data file|Template code
:--|:--
`123.json`|`{{ index .Site.Data "123" }}`
`x123.json`|`{{ index .Site.Data "x123" }}`
`_123.json`|`{{ index .Site.Data "_123" }}`
`x-123.json`|`{{ index .Site.Data "x-123" }}`

## Data files in themes

Data Files can also be used in themes.

However, note that the theme data files are merged with the project directory taking precedence. That is, Given two files with the same name and relative path, the data in the file in the root project `data` directory will override the data from the file in the `themes/<THEME>/data` directory *for keys that are duplicated*).

Therefore, theme authors should be careful not to 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 the 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:

{{< code-toggle file="jacopastorius" >}}
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)"
]
{{< /code-toggle >}}

The list of bass players can be accessed via `.Site.Data.jazz.bass`, a single bass player by adding the file name 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:

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

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

```go-html-template
<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|xml|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:

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

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

## Get remote data

Use `getJSON` or `getCSV` to get remote data:

```go-html-template
{{ $dataJ := getJSON "url" }}
{{ $dataC := getCSV "separator" "url" }}
```

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

```go-html-template
{{ $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:

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

This will resolve internally to the following:

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

### Add HTTP headers

Both `getJSON` and `getCSV` takes an optional map as the last argument, e.g.:

```go-html-template
{{ $data := getJSON "https://example.org/api" (dict "Authorization" "Bearer abcd") }}
```

If you need multiple values for the same header key, use a slice:

```go-html-template
{{ $data := getJSON "https://example.org/api" (dict "X-List" (slice "a" "b" "c")) }}
```

### 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 `$TMPDIR/hugo_cache_$USER/`. 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 [Get Remote Data](#get-remote-data).

{{% note %}}
The local CSV files to be loaded using `getCSV` must be located **outside** 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 data takes a while, Hugo stops processing your Markdown files until the data download has been 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.
{{% /note %}}

## 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]
* [XML Spec][xml]

[config]: /getting-started/configuration/
[csv]: https://tools.ietf.org/html/rfc4180
[customize]: /hugo-modules/theme-components/
[json]: https://www.ecma-international.org/publications/files/ECMA-ST/ECMA-404.pdf
[LiveReload]: /getting-started/usage/#livereload
[lookup]: /templates/lookup-order/
[`markdownify`]: /functions/transform/markdownify
[OAuth]: https://en.wikipedia.org/wiki/OAuth
[partials]: /templates/partials/
[toml]: https://toml.io/en/latest
[variadic]: https://en.wikipedia.org/wiki/Variadic_function
[vars]: /variables/
[yaml]: https://yaml.org/spec/
[xml]: https://www.w3.org/XML/