Variables

Overview

There are a number of ways to include dynamic variables within documents rendered by Quarto. This is useful for externalizing content that varies depending on context, or as an alternative to repeating a value in multiple places (e.g. a version number).

For example, the following prints the title from document metadata:

{{< meta title >}}

The {{< meta >}} syntax used here is an example of a shortcode. Quarto supports the following shortcodes for dynamic variables:

Shortcode	Description
var	Value from _variables.yml file
meta	Value from document metadata
env	Value of System environment variable

var

If you are using a Quarto project, the var shortcode enables you to insert content from a project-level _variables.yml file. Create this file alongside your _quarto.yml project file, and then include references to those variables within any document in your project.

Variables can be either simple values or markdown content. To define variables, create a _variables.yml file in the root directory of your project. For example:

version: 1.2

email:
  info: info@example.com
  support: support@example.com

engine:
  jupyter: "[Jupyter](https://jupyter.org)"
  knitr: "[Knitr](<https://yihui.name/knitr>)"

Note that the engine variable values include markdown for hyperlinks. Any markdown provided needs to be well-formed, and cannot change the structure of the content around it (e.g. by closing a div opened before the variable inclusion).

To include the value of a variable, use the {{< var >}} shortcode, for example:

Version {{< var version >}} is a minor upgrade.

Please contact us at {{< var email.info >}}.

Quarto includes {{< var engine.jupyter >}} and 
{{< var engine.knitr >}} computation engines.

meta

The meta shortcode allows you to insert content from Pandoc metadata (e.g. YAML at the top of the document and/or in _quarto.yml).

For example, the following shortcode inserts the value of the title field from YAML metadata:

{{< meta title >}}

You can dereference sub-keys using the dot (.) delimiter. For example:

{{< meta labels.description >}}

You can also index into an array with the dot (.) delimiter. For example, to extract the first in the array of authors:

{{< meta author.1 >}}

env

The env shortcode enables you to read values from environment variables. For example:

Version {{< env PRODUCT_VERSION >}} is a minor upgrade.

You can provide a fallback value if the environment variable isn’t set by providing a second argument:

Version {{< env PRODUCT_VERSION "*.*" >}} is a minor upgrade.

You can read more about setting environment variables in Quarto projects in Environment Variables.

Escaping

If you are writing documentation about using variable shortcodes (for example, this article!) you might need to prevent them from being processed. You can do this in two ways:

1. Escape the shortcode reference with extra braces like this:

   {{{< var version >}}}

2. Add a shortcodes=false attribute to any code block you want to prevent processing of shortcodes within:

   ```{shortcodes=false}
   {{< var version >}}
   ```