Semver for Design Systems

Semver for design systems adapts the semantic versioning specification to address the unique challenges of versioning component libraries, design tokens, and related tooling. While semver originated for software libraries, design systems present additional complexity due to their visual nature and multi-layer architecture. Applying semver effectively requires clear definitions of what constitutes the public API across different design system layers.

What Is Semver for Design Systems

Semver (semantic versioning) follows the MAJOR.MINOR.PATCH format to communicate change impact through version numbers. For design systems, this convention extends beyond code interfaces to encompass visual APIs, token values, and documentation contracts. Each layer of a design system may have its own public API definition.

The design token layer includes token names, values, and the structure of token files. The component layer includes props, events, slots, CSS classes, and visual appearance. The documentation layer may include code examples that consumers copy directly. Changes to any of these surfaces can impact consuming applications.

How Semver for Design Systems Works

Applying semver to design systems requires establishing clear boundaries around what changes constitute breaking modifications versus backwards-compatible additions or fixes.

For design tokens, renaming or removing tokens constitutes a breaking change requiring a major version. Adding new tokens is backwards-compatible, warranting a minor version. Adjusting token values falls into a gray area that teams must define through their own conventions, as visual changes may or may not be considered breaking.

For components, the traditional semver rules apply to the programmatic API. Breaking changes include removing props, changing prop types incompatibly, altering event signatures, or removing components entirely. Non-breaking additions include new optional props, new components, and additional customization options.

For multi-package design systems, teams must decide whether packages version independently or together. Independent versioning allows packages to evolve at different paces but requires tracking compatibility between packages. Unified versioning simplifies the mental model but may result in version inflation for unchanged packages.

Key Considerations

• Token name changes are breaking even when values remain the same
• Visual regression may warrant major versions depending on team conventions
• Documentation code examples should be tested to prevent copy-paste failures
• Pre-release versions allow testing changes before committing to stable releases
• Changelogs should explain the impact of changes for each version

Common Questions

Should token value changes be treated as breaking changes?

Token value changes present a nuanced versioning decision. From a strict semver perspective, changing a token value does not break the API since the token name remains the same. However, visual changes can significantly impact consumer applications, potentially breaking their designs.

Many design system teams establish conventions around token value changes. Minor adjustments within an established design language may warrant minor versions. Significant visual shifts or values that affect layout may warrant major versions. The key is documenting the convention clearly so consumers understand the implications of different version increments.

How should monorepo design systems handle versioning?

Monorepo design systems can choose between fixed versioning, where all packages share the same version number, or independent versioning, where each package maintains its own version. Each approach has tradeoffs that depend on the design system architecture and consumer needs.

Fixed versioning simplifies understanding which package versions work together. When consumers see version 5.0.0, they know all packages at that version are compatible. The downside is version inflation, where packages receive version bumps even without changes.

Independent versioning allows packages to evolve naturally based on their own change frequency. This approach requires maintaining compatibility documentation showing which package versions work together. Tools like changesets help manage this complexity by tracking changes and determining appropriate version bumps automatically.

Summary

Semver for design systems extends traditional versioning conventions to address the unique challenges of visual libraries. Establishing clear definitions of public APIs across tokens, components, and documentation enables consistent versioning decisions. The choice between fixed and independent versioning depends on organizational needs and tooling capabilities.