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.
Hugo supports loading data from YAML, JSON, and TOML files located in the `data` directory in the root of your Hugo project.
{{<youtubeFyPgSuwIMWQ>}}
## 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:
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-togglefile="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]:
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:
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.
- 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"
