Conditional Content

In some cases you may want to create content that only displays for a given output format (or only displays when not rendering to a format). You can accomplish this by creating divs, spans and code blocks with the .content-visible and .content-hidden classes.

.content-visible

To make content visible only for a given format, you can create a div (:::) with the .content-visible class. For example, here we mark content as only visible in HTML:

::: {.content-visible when-format="html"}

Will only appear in HTML.

:::

You can also set conditions on non-executable code blocks:

```{.python .content-visible when-format="html"}
# code shown only in HTML
2+2
```

To apply a condition only to a part of a paragraph, use a span ([]{}):

Some text
[in HTML.]{.content-visible when-format="html"}
[in PDF.]{.content-visible when-format="pdf"}

You can also mark content as visible for all formats except a specified format. For example:

::: {.content-visible unless-format="pdf"}

Will not appear in PDF.

:::

Then when-format and unless-format attributes match the current Pandoc output format with some additional intelligence to alias related formats (e.g. html, html4, and html5). Details are provided below in Format Matching

when-format and unless-format can also be combined to create more complex conditions:

::: {.content-visible when-format="html" unless-format="revealjs"}

Will only appear in HTML and not in Reveal.js, but actually it appears.

:::

::: {.content-visible when-format="revealjs"}

Will only appear in Reveal.js and not in HTML or other formats.

:::

.content-hidden

To prevent content from being displayed when rendering to a given format, use the .content-hidden class. For example, here we mark content as hidden in HTML:

::: {.content-hidden when-format="html"}

Will not appear in HTML.

:::

You can also mark content as hidden for all formats except a specified format. For example:

::: {.content-hidden unless-format="pdf"}

Will only appear in PDF.

:::

Format Matching

The when-format and unless-format clauses do some aliasing of related formats to make it more straightforward to target content. The following aliases are implemented:

Alias	Formats
latex	latex, pdf
pdf	latex, pdf
epub	epub*
html	html*, epub*, revealjs
html:js	html*, revealjs
markdown	markdown*, commonmark*, gfm, markua

Note that the html:js alias indicates that the target format is capable of executing JavaScript (this maps to all HTML formats save for ePub).

Matching against metadata

It’s possible to match against boolean metadata values. Use the attributes unless-meta and when-meta, and use periods . to separate metadata keys. For example:

::: {.content-hidden unless-meta="path.to.metadata"}

This content will be hidden unless there exists a metadata entry like such:

```yml
path:
  to:
    metadata: true
```

:::

This feature is often useful alongside project profiles. Different profiles can set different metadata values, and so can control the metadata used in conditional content.