A design system is a governed product, not merely a component library

A component library distributes interface code, while a design system coordinates broader product decisions.

It combines principles, tokens, patterns, components, content guidance, documentation, ownership, and contribution processes.

USWDS describes an active community around reusable solutions, rather than presenting code as the entire system.

Without governance, duplicated exceptions accumulate until shared components no longer represent reliable organizational standards.

Semantic tokens preserve intent across themes and platforms connects shared design decisions directly to implementation.

Contribution criteria prevent design systems from becoming component dumps controls evolution through evidence and review.

These layers create a maintained product that serves other product teams through stable contracts.

Judge maturity by adoption, ownership, feedback, and upgrade discipline, not simply by component count.