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.
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, 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.
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.
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).
