Astro uses the open source typeface Open Sans with bold, regular and light font variants for all heading, body copy and most interface elements. Astro also uses the open source typeface Roboto Mono for elements requiring a monospaced typeface. As with all Astro elements, sizing is rendered in rem units. For those working with systems that don’t support rem, the corollary size is provided in points.


Astro supports three levels of headline text (h1, h2, h3). CSS properties are automatically applied to HTML elements.

Heading Weight Markup REM PX Class
Heading Level 1 Light <h1> 2.375 38 .h1
Heading Level 2 Light <h2> 1.75 28 .h2
Heading Level 3 Light <h3> 1.375 22 .h3

In addition to semantic headings, Astro supports overriding a header element's presentation via .h1, .h2 .h3 CSS classes which will apply the visual appearance of the corresponding header element.

Body Text

The default font size in Astro is 1rem/16px. Astro supports four additional font sizes for body copy.

Size Weight REM PX Class
Extra large Normal 1.125 18 .xl
Normal/large Normal 1 16 --
Medium Normal 0.875 14 .md
Small Normal 0.75 12 .sm
Extra small Normal 0.65 10 .xs

Inline Text Styles

Sample Class
Link Color --
Low Contrast* .low-contrast
Inverted Text Style .inverted

* The low contrast text option will fail WCAG readability compliance