A format specification for describing a visual identity to coding agents. DESIGN.md gives agents a persistent, structured understanding of a design system.

A DESIGN.md file combines machine-readable design tokens (YAML front matter) with human-readable design rationale (markdown prose). Tokens give agents exact values. Prose tells them why those values exist and how to apply them.

---
name: Heritage
colors:
 primary: "#1A1C1E"
 secondary: "#6C7278"
 tertiary: "#B8422E"
 neutral: "#F7F5F2"
typography:
 h1:
 fontFamily: Public Sans
 fontSize: 3rem
 body-md:
 fontFamily: Public Sans
 fontSize: 1rem
 label-caps:
 fontFamily: Space Grotesk
 fontSize: 0.75rem
rounded:
 sm: 4px
 md: 8px
spacing:
 sm: 8px
 md: 16px
---
## Overview
Architectural Minimalism meets Journalistic Gravitas. The UI evokes a
premium matte finish — a high-end broadsheet or contemporary gallery.
## Colors
The palette is rooted in high-contrast neutrals and a single accent color.
- **Primary (#1A1C1E):** Deep ink for headlines and core text.
- **Secondary (#6C7278):** Sophisticated slate for borders, captions, metadata.
- **Tertiary (#B8422E):** "Boston Clay" — the sole driver for interaction.
- **Neutral (#F7F5F2):** Warm limestone foundation, softer than pure white.

An agent that reads this file will produce a UI with deep ink headlines in Public Sans, a warm limestone background, and Boston Clay call-to-action buttons.

Validate a DESIGN.md against the spec, catch broken token references, check WCAG contrast ratios, and surface structural findings — all as structured JSON that agents can act on.

npx @google/design.md lint DESIGN.md

{
 "findings": [
 {
 "severity": "warning",
 "path": "components.button-primary",
 "message": "textColor (#ffffff) on backgroundColor (#1A1C1E) has contrast ratio 15.42:1 — passes WCAG AA."
 }
 ],
 "summary": { "errors": 0, "warnings": 1, "info": 1 }
}

Compare two versions of a design system to detect token-level and prose regressions:

npx @google/design.md diff DESIGN.md DESIGN-v2.md

{
 "tokens": {
 "colors": { "added": ["accent"], "removed": [], "modified": ["tertiary"] },
 "typography": { "added": [], "removed": [], "modified": [] }
 },
 "regression": false
}

The full DESIGN.md spec lives at docs/spec.md. What follows is a condensed reference.

A DESIGN.md file has two layers:

1. YAML front matter — Machine-readable design tokens, delimited by --- fences at the top of the file.
2. Markdown body — Human-readable design rationale organized into ## sections.

The tokens are the normative values. The prose provides context for how to apply them.

version: <string> # optional, current: "alpha"
name: <string>
description: <string> # optional
colors:
 <token-name>: <Color>
typography:
 <token-name>: <Typography>
rounded:
 <scale-level>: <Dimension>
spacing:
 <scale-level>: <Dimension | number>
components:
 <component-name>:
 <token-name>: <string | token reference>

Sections use ## headings. They can be omitted, but those present must appear in this order:

Components map a name to a group of sub-token properties:

components:
 button-primary:
 backgroundColor: "{colors.tertiary}"
 textColor: "{colors.on-tertiary}"
 rounded: "{rounded.sm}"
 padding: 12px
 button-primary-hover:
 backgroundColor: "{colors.tertiary-container}"

Valid component properties: backgroundColor, textColor, typography, rounded, padding, size, height, width.

Variants (hover, active, pressed) are expressed as separate component entries with a related key name.

npm install @google/design.md

On Windows, quote the package name if your shell treats @ specially (PowerShell, some terminals):

npm install "@google/design.md"

Or run directly (always resolves from the public npm registry):

npx @google/design.md lint DESIGN.md

On Windows/PowerShell, this direct form can produce no output (or open DESIGN.md in your Markdown editor) because the .md suffix in the design.md bin name collides with the Windows Markdown file association during command resolution. Run the dot-free designmd alias instead — point npx at the package with -p, then invoke designmd:

npx -p @google/design.md designmd lint DESIGN.md

The designmd shim resolves to the same entrypoint and works identically across all platforms.

The CLI is published as @google/design.md on npm. ENOVERSIONS almost always means npm is not querying the public registry (custom registry= in .npmrc, a corporate mirror that has not synced this package, or a misconfigured @google:registry for the @google scope).

Check your effective registry:

npm config get registry

For a normal install from the internet it should be https://registry.npmjs.org/. After fixing config, retry with npm cache clean --force if a stale 404 was cached.

All commands accept a file path or - for stdin. Output defaults to JSON.

Windows tip: when invoking the CLI directly from a package.json script (rather than through npx), use the designmd alias instead of design.md. The .md suffix in the original bin name confuses Windows command resolution with the file association for Markdown files. The designmd shim resolves to the same entrypoint and works identically across all platforms.

// package.json
{
 "scripts": {
 "design:lint": "designmd lint DESIGN.md"
 }
}

Validate a DESIGN.md file for structural correctness.

npx @google/design.md lint DESIGN.md
npx @google/design.md lint --format json DESIGN.md
cat DESIGN.md | npx @google/design.md lint -

Exit code 1 if errors are found, 0 otherwise.

Compare two DESIGN.md files and report token-level changes.

npx @google/design.md diff DESIGN.md DESIGN-v2.md

Exit code 1 if regressions are detected (more errors or warnings in the "after" file).

Export DESIGN.md tokens to other formats.

npx @google/design.md export --format json-tailwind DESIGN.md > tailwind.theme.json
npx @google/design.md export --format css-tailwind DESIGN.md > theme.css
npx @google/design.md export --format dtcg DESIGN.md > tokens.json

Output the DESIGN.md format specification (useful for injecting spec context into agent prompts).

npx @google/design.md spec
npx @google/design.md spec --rules
npx @google/design.md spec --rules-only --format json

The linter runs nine rules against a parsed DESIGN.md. Each rule produces findings at a fixed severity level.

The linter is also available as a library:

import { lint } from '@google/design.md/linter';
const report = lint(markdownString);
console.log(report.findings); // Finding[]
console.log(report.summary); // { errors, warnings, info }
console.log(report.designSystem); // Parsed DesignSystemState

DESIGN.md tokens are inspired by the W3C Design Token Format. The export command converts tokens to other formats:

• Tailwind v3 config (JSON) — npx @google/design.md export --format json-tailwind DESIGN.md — emits a theme.extend JSON object for tailwind.config.js. --format tailwind is a backwards-compatible alias.
• Tailwind v4 theme (CSS) — npx @google/design.md export --format css-tailwind DESIGN.md — emits a CSS @theme { ... } block using Tailwind v4's CSS-variable token namespaces (--color-*, --font-*, --text-*, --leading-*, --tracking-*, --font-weight-*, --radius-*, --spacing-*).
• DTCG tokens.json (W3C Design Tokens Format Module) — npx @google/design.md export --format dtcg DESIGN.md

The DESIGN.md format is at version alpha. The spec, token schema, and CLI are under active development. Expect changes to the format as it matures.

This project is not eligible for the Google Open Source Software Vulnerability Rewards Program.