Callout title is not inline content
title= attribute parses to block content, so it cannot fill the title and is ignored.
Q-2-44 — Callout title is not inline content
A callout title must be a single line of inline markdown. This value parses to block content, so it is ignored.
What this means
A callout’s title= attribute is parsed as markdown, so inline markup
works and renders in the callout header:
::: {.callout-tip title="Use `renv` for reproducibility"}
Body.
:::The header shows Use renv for reproducibility with a real code span.
A callout header can only hold inline content, though. If the value
parses to block content — because it begins with a block marker such as
#, or contains a blank line — there is nothing sensible to put in the
header, so the attribute is ignored. The callout still renders, falling
back to a leading heading if there is one, or to the callout type’s name.
Why this happens
- A
#at the start of the value.title="# Overview"parses as a heading, not as text beginning with a#character. - A blank line inside the value, which splits it into two paragraphs.
- Other leading block markers —
>,-,1., or an indented code block.
How to fix
Write the title as plain inline markdown:
::: {.callout-note title="Overview"}
Body.
:::To show a literal # at the start of a title, escape it with two
backslashes:
::: {.callout-note title="\\# Overview"}
Body.
:::Two escaping layers apply in sequence here, and one backslash is not
enough. Attribute values are unescaped first, which turns \# into a
plain # — and the markdown parser then reads that as a heading, which
is the very error you were trying to avoid. Writing \\# survives the
first layer as \#, which the markdown parser reads as an escaped,
literal #.
If you meant to add block content, put it in the callout body rather than the title:
::: {.callout-note title="Overview"}
## A heading in the body
Body.
:::Note that a heading as the callout’s first block is treated as its
title — see Q-2-43.