Labels are just a simple Bootstrap component that you can include in your pages as needed. They represent one of many Bootstrap options you can include in your theme.
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About labels

Labels might come in handy for adding button-like tags next to elements, such as POST, DELETE, UPDATE methods for endpoints. You can use any classes from Bootstrap in your content.

<span class="label label-default">Default</span>
<span class="label label-primary">Primary</span>
<span class="label label-success">Success</span>
<span class="label label-info">Info</span>
<span class="label label-warning">Warning</span>
<span class="label label-danger">Danger</span>

Default Primary Success Info Warning Danger

You can have a label appear within a heading simply by including the span tag in the heading. However, you can’t mix Markdown syntax with HTML, so you’d have to hard-code the heading ID for the auto-TOC to work.

Tags: formatting