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---
title: Passthrough render hooks
linkTitle: Passthrough
description: Create a passthrough render hook to override the rendering of text snippets captured by the Goldmark passthrough extension.
categories: [render hooks]
keywords: []
menu:
docs:
parent: render-hooks
weight: 80
weight: 80
toc: true
---
{{< new-in 0.132.0 >}}
## Overview
Hugo uses [Goldmark] to render Markdown to HTML. Goldmark supports custom extensions to extend its core functionality. The Goldmark [passthrough extension] captures and preserves raw Markdown within delimited snippets of text, including the delimiters themselves. These are known as _passthrough elements_.
[Goldmark]: https://github.com/yuin/goldmark
[passthrough extension]: /getting-started/configuration-markup/#passthrough
Depending on your choice of delimiters, Hugo will classify a passthrough element as either _block_ or _inline_. Consider this contrived example:
{{< code file=content/sample.md >}}
This is a
\[block\]
passthrough element with opening and closing block delimiters.
This is an \(inline\) passthrough element with opening and closing inline delimiters.
{{< /code >}}
Update your site configuration to enable the passthrough extension and define opening and closing delimiters for each passthrough element type, either `block` or `inline`. For example:
{{< code-toggle file=hugo >}}
[markup.goldmark.extensions.passthrough]
enable = true
[markup.goldmark.extensions.passthrough.delimiters]
block = [['\[', '\]'], ['$$', '$$']]
inline = [['\(', '\)']]
{{< /code-toggle >}}
In the example above there are two sets of `block` delimiters. You may use either one in your Markdown.
The Goldmark passthrough extension is often used in conjunction with the MathJax or KaTeX display engine to render [mathematical expressions] written in [LaTeX] or [Tex].
[mathematical expressions]: /content-management/mathematics/
[LaTeX]: https://www.latex-project.org/
[Tex]: https://en.wikipedia.org/wiki/TeX
To enable custom rendering of passthrough elements, create a render hook.
## Context
Passthrough render hook templates receive the following [context]:
[context]: /getting-started/glossary/#context
###### Attributes
(`map`) The [Markdown attributes], available if you configure your site as follows:
[Markdown attributes]: /content-management/markdown-attributes/
{{< code-toggle file=hugo >}}
[markup.goldmark.parser.attribute]
block = true
{{< /code-toggle >}}
Hugo populates the `Attributes` map for _block_ passthrough elements. Markdown attributes are not applicable to _inline_ elements.
###### Inner
(`string`) The inner content of the passthrough element, excluding the delimiters.
###### Ordinal
(`int`) The zero-based ordinal of the passthrough element on the page.
###### Page
(`page`) A reference to the current page.
###### PageInner
(`page`) A reference to a page nested via the [`RenderShortcodes`] method. [See details](#pageinner-details).
[`RenderShortcodes`]: /methods/page/rendershortcodes
###### Position
(`string`) The position of the passthrough element within the page content.
###### Type
(`bool`) The passthrough element type, either `block` or `inline`.
## Example
As an alternative to rendering mathematical expressions with the MathJax or KaTeX display engine, create a passthrough render hook which calls the [`transform.ToMath`] function:
[`transform.ToMath`]: /functions/transform/tomath/
{{< code file=layouts/_default/_markup/render-passthrough.html copy=true >}}
{{ if eq .Type "block" }}
{{ $opts := dict "displayMode" true }}
{{ transform.ToMath .Inner $opts }}
{{ else }}
{{ transform.ToMath .Inner }}
{{ end }}
{{< /code >}}
Although you can use one template with conditional logic as shown above, you can also create separate templates for each [`Type`](#type) of passthrough element:
```text
layouts/
└── _default/
└── _markup/
├── render-passthrough-block.html
└── render-passthrough-inline.html
```
{{% include "/render-hooks/_common/pageinner.md" %}}
|
