WikiText can include blocks of text that are rendered with an explicit ContentType like this:

$$$image/svg+xml
<svg xmlns="http://www.w3.org/2000/svg" width="150" height="100">
  <circle cx="100" cy="50" r="40" stroke="black" stroke-width="2" fill="green" />
</svg>
$$$

This renders as:

It is also possible to abbreviate the ContentType to a file extension. For example:

$$$.svg
<svg xmlns="http://www.w3.org/2000/svg" width="150" height="100">
  <circle cx="100" cy="50" r="40" stroke="black" stroke-width="2" fill="red" />
</svg>
$$$

This renders as:

Unknown types render as plain text:

$$$text/unknown
Some plain text, which will not be //formatted//.
$$$

Which renders as:

Some plain text, which will not be //formatted//.

A render type can also be specified, causing a particular text rendering to be displayed. For example:

$$$text/vnd.tiddlywiki>text/html
This is ''some'' wikitext
$$$

$$$text/vnd.tiddlywiki>text/plain
This is ''some'' wikitext
$$$

Renders as:

<p>This is <strong>some</strong> wikitext</p>

This is some wikitext