Intent to Implement and Ship: The “system-ui” generic font family

Contact emails

Spec

CSS Fonts Level 4, 10. New generic font families

https://drafts.csswg.org/css-fonts-4/#valdef-font-family-system-ui

Summary

This generic font family allows authors to style contents so it fits within the system UI.

Motivation

The web does this today either by listing all known system family in their CSS, or by relying on vendor-specific extensions. This new generic font family allows the standardized way to use the system font, on all platforms Blink supports.

The original CSS WG discussion proposed by Apple is here.

Interoperability and Compatibility Risk

Low.

Blink on Mac already ships this functionality as non-standard “BlinkMacSystemFont”. Shipping “system-ui” means to use the standardized name and support other platforms. Old name will be kept as an alias on Mac, and its usage will be measured for the deprecation.
CSS.supports() cannot detect font families, and doing so has privacy concerns, but font fallback allows authors to write robust CSS.
Further risk is considered to be low.

Web developers: Positive.

WebKit: Shipped “-apple-system”, has a bug to alias to “system-ui”.

Gecko: Positive (tracking bug). Shipped “-apple-system” for the compat with WebKit.

Edge: No public signals.

Ongoing technical constraints

None.

Will this feature be supported on all six Blink platforms (Windows, Mac, Linux, Chrome OS, Android, and Android WebView)?

Yes.

OWP launch tracking bug

https://crbug.com/654679

Link to entry on the feature dashboard

https://www.chromestatus.com/feature/5640395337760768

Requesting approval to ship?

Yes.