+++
title = "Overview"
weight = 10
+++

Zola uses the [Tera](https://tera.netlify.com) template engine, which is very similar
to Jinja2, Liquid and Twig.

As this documentation will only talk about how templates work in Zola, please read
the [Tera template documentation](https://tera.netlify.com/docs#templates) if you want
to learn more about it first.

All templates live in the `templates` directory.  If you are not sure what variables are available in a template,
you can place `{{ __tera_context }}` in the template to print the whole context.

A few variables are available on all templates except feeds and the sitemap:

- `config`: the language aware [configuration](@/documentation/getting-started/configuration.md)
- `current_path`: the path (full URL without `base_url`) of the current page, always starting with a `/`
- `current_url`: the full URL for the current page
- `lang`: the language for the current page

Config variables can be accessed like `config.variable`, in HTML for example with `{{ config.base_url }}`.
The 404 template does not get `current_path` and `current_url` (this information cannot be determined).

On top of the `config` attributes mentioned above, it also gets `config.mode` which is whether it's run in `build`, `serve` or `check`.

## Standard templates
By default, Zola will look for three templates: `index.html`, which is applied
to the site homepage; `section.html`, which is applied to all sections (any HTML
page generated by creating a directory within your `content` directory); and
`page.html`, which is applied to all pages (any HTML page generated by creating an
`.md` file within your `content` directory).

The homepage is always a section (regardless of whether it contains other pages).
Thus, the `index.html` and `section.html` templates both have access to the
section variables.  The `page.html` template has access to the page variables.
The page and section variables are described in more detail in the next section.

## Built-in templates
Zola comes with four built-in templates: `atom.xml` and `rss.xml` (described in
[Feeds](@/documentation/templates/feeds/index.md)), `sitemap.xml` (described in [Sitemap](@/documentation/templates/sitemap.md)),
and `robots.txt` (described in [Robots.txt](@/documentation/templates/robots.md)).
Additionally, themes can add their own templates, which will be applied if not
overridden.  You can override built-in or theme templates by creating a template with
the same name in the correct path. For example, you can override the Atom template by
creating a `templates/atom.xml` file.

## Custom templates
In addition to the standard `index.html`, `section.html` and `page.html` templates,
you may also create custom templates by creating an `.html` file in the `templates`
directory.  These custom templates will not be used by default.  Instead, a custom template will _only_ be used if you apply it by setting the `template` front-matter variable to the path for that template (or if you `include` it in another template that is applied).  For example, if you created a custom template for your site's About page called `about.html`, you could apply it to your `about.md` page by including the following front matter in your `about.md` page:

```md
+++
title = "About Us"
template = "about.html"
+++
```

Custom templates are not required to live at the root of your `templates` directory.
For example, `product_pages/with_pictures.html` is a valid template.

## Built-in filters
Zola adds a few filters in addition to [those](https://tera.netlify.com/docs/#filters) already present
in Tera.

### markdown
Converts the given variable to HTML using Markdown. There are a few differences compared to page/section Markdown rendering:

- shortcodes evaluated by this filter cannot access the current rendering context: `config` will be available, but accessing `section` or `page` (among others) from a shortcode called within the `markdown` filter will prevent your site from building (see [this discussion](https://github.com/getzola/zola/pull/1358))
- `lang` in shortcodes will always be equal to the site's `default_lang` (or `en` otherwise) ; it should not be a problem, but if it is in most cases, but if you need to use language-aware shortcodes in this filter, please refer to the [Shortcode context](@/documentation/content/shortcodes.md#shortcode-context) section of the docs.

By default, the filter will wrap all text in a paragraph. To disable this behaviour, you can
pass `true` to the inline argument:

```jinja2
{{ some_text | markdown(inline=true) }}
```

You do not need to use this filter with `page.content` or `section.content`, the content is already rendered.

### base64_encode
Encode the variable to base64.

### base64_decode
Decode the variable from base64.

### num_format
Format a number into its string representation.

```jinja2
{{ 1000000 | num_format }}
<!-- 1,000,000 -->
```

By default this will format the number using the locale set by `config.default_language` in config.toml.

To format a number for a specific locale, you can use the `locale` argument and pass the name of the desired locale:

```jinja2
{{ 1000000 | num_format(locale="en-IN") }}
<!-- 10,00,000 -->
```

## Built-in functions

Zola adds a few Tera functions to [those built-in in Tera](https://tera.netlify.com/docs#built-in-functions)
to make it easier to develop complex sites.

### File searching logic
For functions that are searching for a file on disk other than through `get_page` and `get_section`, the following
logic applies.

1. The base directory is the Zola root directory, where the `config.toml` is
2. For the given path: if it starts with `@/`, replace that with `content/` instead and trim any leading `/`
3. Search in the following locations in this order, returning the first where the file exists:
   1. $base_directory + $path
   2. $base_directory + "static/" + $path
   3. $base_directory + "content/" + $path
   4. $base_directory + $output_path + $path
   5. $base_directory + "themes" + $theme + "static/" + $path (only if using a theme)

In practice this means that `@/some/image.jpg`, `/content/some/image.jpg` and `content/some/image.jpg` will point to the
same thing.

It will error if the path is outside the Zola directory.

### `get_page`
Takes a path to an `.md` file and returns the associated page. The base path is the `content` directory.

```jinja2
{% set page = get_page(path="blog/page2.md") %}
```

### `get_section`
Takes a path to an `_index.md` file and returns the associated section. The base path is the `content` directory.

```jinja2
{% set section = get_section(path="blog/_index.md") %}
```

If you only need the metadata of the section, you can pass `metadata_only=true` to the function:

```jinja2
{% set section = get_section(path="blog/_index.md", metadata_only=true) %}
```

### `get_taxonomy_url`
Gets the permalink for the taxonomy item found.

```jinja2
{% set url = get_taxonomy_url(kind="categories", name=page.taxonomies.category, lang=page.lang) %}
```

`name` will almost always come from a variable but in case you want to do it manually,
the value should be the same as the one in the front matter, not the slugified version.

`lang` (optional) default to `config.default_language` in config.toml

`required` (optional) if a taxonomy is defined but there isn't any content that uses it then throw an error. Defaults to true.

### `get_taxonomy`
Gets the whole taxonomy of a specific kind.

```jinja2
{% set categories = get_taxonomy(kind="categories") %}
```

The type of the output is:

```ts
kind: TaxonomyConfig;
items: Array<TaxonomyTerm>;
```

`lang` (optional) default to `config.default_language` in config.toml

`required` (optional) if a taxonomy is defined but there isn't any content that uses it then throw an error. Defaults to true.

See the [Taxonomies documentation](@/documentation/templates/taxonomies.md) for a full documentation of those types.

### `get_url`
Gets the permalink for the given path.
If the path starts with `@/`, it will be treated as an internal link like the ones used in Markdown, 
starting from the root `content` directory as well as validated.

```jinja2
{% set url = get_url(path="@/blog/_index.md") %}
```

It accepts an optional parameter `lang` in order to compute a *language-aware URL* in multilingual websites. Assuming `config.base_url` is `"http://example.com"`, the following snippet will:

- return `"http://example.com/blog/"` if `config.default_language` is `"en"`
- return `"http://example.com/en/blog/"` if `config.default_language` is **not** `"en"` and `"en"` appears in `config.languages`
- fail otherwise, with the error message `"'en' is not an authorized language (check config.languages)."`

```jinja2
{% set url = get_url(path="@/blog/_index.md", lang="en") %}
```

This can also be used to get the permalinks for static assets, for example if
we want to link to the file that is located at `static/css/app.css`:

```jinja2
{{/* get_url(path="css/app.css") */}}
```

By default, assets will not have a trailing slash. You can force one by passing `trailing_slash=true` to the `get_url` function.
An example is:

```jinja2
{{/* get_url(path="css/app.css", trailing_slash=true) */}}
```

In the case of non-internal links, you can also add a cachebust of the format `?h=<sha256>` at the end of a URL
by passing `cachebust=true` to the `get_url` function. In this case, the path will need to resolve to an actual file. 
See [File Searching Logic](@/documentation/templates/overview.md#file-searching-logic) for details.

### `get_file_hash`

Returns the hash digest (SHA-256, SHA-384 or SHA-512) of a file.

It can take the following arguments:
- `path`: mandatory, see [File Searching Logic](@/documentation/templates/overview.md#file-searching-logic) for details
- `sha_type`: optional, one of `256`, `384` or `512`, defaults to `384`
- `base64`: optional, `true` or `false`, defaults to `true`. Whether to encode the hash as base64

```jinja2
{{/* get_file_hash(path="static/js/app.js", sha_type=256) */}}
```

The function can also output a base64-encoded hash value when its `base64`
parameter is set to `true`. This can be used to implement [subresource
integrity](https://developer.mozilla.org/en-US/docs/Web/Security/Subresource_Integrity).

```jinja2
<script src="{{/* get_url(path="static/js/app.js") */}}"
  integrity="sha384-{{ get_file_hash(path="static/js/app.js", sha_type=384, base64=true) | safe }}"></script>
```

Do note that subresource integrity is typically used when using external scripts, which `get_file_hash` does not support.

### `get_image_metadata`

Gets metadata for an image. This supports common formats like JPEG, PNG, WebP, BMP, GIF as well as SVG.

It can take the following arguments:

- `path`: mandatory, see [File Searching Logic](@/documentation/templates/overview.md#file-searching-logic) for details
- `allow_missing`: optional, `true` or `false`, defaults to `false`. Whether a missing file should raise an error or not.

The method returns a map containing `width`, `height` and `format` (the lowercased value as string).

```jinja2
  {% set meta = get_image_metadata(path="...") %}
  Our image (.{{meta.format}}) has format is {{ meta.width }}x{{ meta.height }}
```

### `load_data`

Loads data from a file, URL, or string literal. Supported file types include *toml*, *json*, *csv*, *bibtex*, *yaml* 
and *xml* and only supports UTF-8 encoding.

Any other file type will be loaded as plain text.

The `path` argument specifies the path to a local data file, according to the [File Searching Logic](@/documentation/templates/overview.md#file-searching-logic).

```jinja2
{% set data = load_data(path="content/blog/story/data.toml") %}
```

Alternatively, the `url` argument specifies the location of a remote URL to load.

```jinja2
{% set data = load_data(url="https://en.wikipedia.org/wiki/Commune_of_Paris") %}
```

Alternatively, the `literal` argument specifies an object literal. Note: if the `format` argument is not specified, then plain text will be what is assumed.

```jinja2
{% set data = load_data(literal='{"name": "bob"}', format="json") %}
{{ data["name"] }}
```

*Note: the `required` parameter has no effect when used in combination with the `literal` argument.*

The optional `required` boolean argument can be set to false so that missing data (HTTP error or local file not found) does not produce an error, but returns a null value instead. However, permission issues with a local file and invalid data that could not be parsed to the requested data format will still produce an error even with `required=false`.

The snippet below outputs the HTML from a Wikipedia page, or "No data found" if the page was not reachable, or did not return a successful HTTP code:

```jinja2
{% set data = load_data(url="https://en.wikipedia.org/wiki/Commune_of_Paris", required=false) %}
{% if data %}{{ data | safe }}{% else %}No data found{% endif %}
```

The optional `format` argument allows you to specify and override which data type is contained within the specified file or URL.
Valid entries are `toml`, `json`, `csv`, `bibtex`, `yaml`, `xml` or `plain`. If the `format` argument isn't specified, then the 
path extension is used. In the case of a literal, `plain` is assumed if `format` is unspecified.


```jinja2
{% set data = load_data(path="content/blog/story/data.txt", format="json") %}
```

Use the `plain` format for when your file has a supported extension but you want to load it as plain text.

For *toml*, *json*, *yaml* and *xml*, the data is loaded into a structure matching the original data file;
however, for *csv* there is no native notion of such a structure. Instead, the data is separated
into a data structure containing *headers* and *records*. See the example below to see
how this works.

In the template:
```jinja2
{% set data = load_data(path="content/blog/story/data.csv") %}
```

In the *content/blog/story/data.csv* file:
```csv
Number, Title
1,Gutenberg
2,Printing
```

The equivalent json value of the parsed data would be stored in the `data` variable in the
template:
```json
{
    "headers": ["Number", "Title"],
    "records": [
        ["1", "Gutenberg"],
        ["2", "Printing"]
    ],
}
```

The `bibtex` format loads data into a structure matching the format used by the
[nom-bibtex crate](https://crates.io/crates/nom-bibtex). The following is an example of data
in bibtex format:

```
@preamble{"A bibtex preamble" # " this is."}

@Comment{
    Here is a comment.
}

Another comment!

@string(name = "Vincent Prouillet")
@string(github = "https://github.com/getzola/zola")

@misc {my_citation_key,
    author= name,
    title = "Zola",
    note = "github: " # github
}                                                    }
```

The following is the json-equivalent format of the produced bibtex data structure:
```json
{
    "preambles": ["A bibtex preamble this is."],
    "comments": ["Here is a comment.", "Another comment!"],
    "variables": {
        "name": "Vincent Prouillet",
        "github": "https://github.com/getzola/zola"
    },
    "bibliographies": [
        {
            "entry_type": "misc",
            "citation_key": "my_citation_key",
            "tags": {
                "author": "Vincent Prouillet",
                "title": "Zola",
                "note": "github: https://github.com/getzola/zola"
            }
        }
    ]
}
```

Finally, the bibtex data can be accessed from the template as follows:
```jinja2
{% set tags = data.bibliographies[0].tags %}
This was generated using {{ tags.title }}, authored by {{ tags.author }}.
```

#### Remote content

Instead of using a file, you can load data from a remote URL. This can be done by specifying a `url` parameter
to `load_data` rather than `path`.

```jinja2
{% set response = load_data(url="https://api.github.com/repos/getzola/zola") %}
{{ response }}
```

By default, the response body will be returned with no parsing. This can be changed by using the `format` argument
as below.


```jinja2
{% set response = load_data(url="https://api.github.com/repos/getzola/zola", format="json") %}
{{ response }}
```

When no other parameters are specified the URL will always be retrieved using a HTTP GET request.
Using the parameter `method`, since version 0.14.0, you can also choose to retrieve the URL using a POST request.

When using `method="POST"` you can also use the parameters `body` and `content_type`.
The parameter body is the actual contents sent in the POST request.
The parameter `content_type` should be the mimetype of the body.

This example will make a POST request to the kroki service to generate a SVG.

```jinja2
{% set postdata = load_data(url="https://kroki.io/blockdiag/svg", format="plain", method="POST" ,content_type="text/plain", body="blockdiag {
  'Doing POST' -> 'using load_data'
  'using load_data' -> 'can generate' -> 'block diagrams';
  'using load_data' -> is -> 'very easy!';

  'Doing POST' [color = 'greenyellow'];
  'block diagrams' [color = 'pink'];
  'very easy!' [color = 'orange'];
}")%}
{{postdata|safe}}
```

If you need additional handling for the HTTP headers, you can use the `headers` parameter.
You might need this parameter when the resource requires authentication or require passing additional
parameters via special headers.
Please note that the headers will be appended to the default headers set by Zola itself instead of replacing them.

This example will make a POST request to the GitHub markdown rendering service.

```jinja2
{% set postdata = load_data(url="https://api.github.com/markdown", format="plain", method="POST", content_type="application/json", headers=["accept=application/vnd.github.v3+json"], body='{"text":"headers support added in #1710, commit before it: b3918f124d13ec1bedad4860c15a060dd3751368","context":"getzola/zola","mode":"gfm"}')%}
{{postdata|safe}}
```

The following example shows how to send a GraphQL query to GitHub (requires authentication).
If you want to try this example on your own machine, you need to provide a GitHub PAT (Personal Access Token),
you can acquire the access token at this link: https://github.com/settings/tokens and then set `GITHUB_TOKEN`
environment variable to the access token you have obtained.

```jinja2
{% set token = get_env(name="GITHUB_TOKEN") %}
{% set postdata = load_data(url="https://api.github.com/graphql", format="json", method="POST" ,content_type="application/json", headers=["accept=application/vnd.github.v4.idl", "authentication=Bearer " ~ token], body='{"query":"query { viewer { login }}"}')%}
{{postdata|safe}}
```

In case you need to specify multiple headers with the same name, you can specify them like this:

```
headers=["accept=application/json,text/html"]
```

Which is equivalent to two `Accept` headers with `application/json` and `text/html`.

If it doesn't work, you can instead specify the headers multiple times to achieve a similar effect:

```
headers=["accept=application/json", "accept=text/html"]
```

#### Data caching

Data file loading and remote requests are cached in memory during the build, so multiple requests aren't made
to the same endpoint.
URLs are cached based on the URL, and data files are cached based on the file modified time.
The format is also taken into account when caching, so a request will be sent twice if it's loaded with two
different formats.

### `trans`
Gets the translation of the given `key`, for the `default_language`, the `lang`uage given or the active language:

```jinja2
{{/* trans(key="title") */}}
{{/* trans(key="title", lang="fr") */}}
{{/* trans(key="title", lang=lang) */}}
```

### `resize_image`
Resizes an image file.
Please refer to [_Content / Image Processing_](@/documentation/content/image-processing/index.md) for complete documentation.
