Atlassian Design System (ADS) powers the UI across Jira, Confluence, and Atlassian's other products, built around design tokens as the single source of truth for color, spacing, and typography, shipped as installable @atlaskit npm packages.
It's strongest in its token architecture: the same token set drives light, dark, and high-contrast themes automatically, so switching themes doesn't require separately maintained color values per mode.
Design system engineers who want to study a mature token-first architecture (not merely a component gallery) that actually ships as real, versioned packages.
The token documentation is genuinely deep, worth studying even outside an Atlassian context as a reference for how semantic naming should separate raw values from their usage.
Atlassian's own design system.
