design-token-extractor

A one-command CLI that extracts a W3C DTCG-compatible design token set from any public website or local HTML file.

Install

npm i -g @ai.to.design/design-token-extractor
npx playwright install chromium

Requires Node.js >= 18. The Chromium download is a one-time ~200 MB.

Usage

Extract from a URL

design-token-extractor extract https://example.com --out tokens.json

Extract from a local HTML file (bypasses auth walls)

design-token-extractor extract --file ./page.html --out tokens.json

Output formats

# W3C DTCG JSON (default) — canonical
design-token-extractor extract https://example.com --format json --out tokens.json

# CSS custom properties under :root (+ @media prefers-color-scheme: dark)
design-token-extractor extract https://example.com --format css --out tokens.css

# ES module exporting a default object
design-token-extractor extract https://example.com --format js  --out tokens.js

# Markdown with color swatches and usage tables
design-token-extractor extract https://example.com --format md  --out tokens.md

Filter low-confidence tokens

Each token is scored 0..1 based on how many selectors use it. Drop one-offs:

design-token-extractor extract https://example.com --min-confidence 0.5

Theme emulation

design-token-extractor extract https://example.com --theme auto    # default; emits both if dark rules exist
design-token-extractor extract https://example.com --theme light
design-token-extractor extract https://example.com --theme dark

Output shape (DTCG)

Tokens follow the W3C Design Tokens Community Group draft. Each token is a $value / $type / $extensions envelope:

{
  "color": {
    "color-1": {
      "$value": "#3b82f6",
      "$type": "color",
      "$extensions": {
        "com.dte.usage": { "selectors": ["button.primary", "a"], "count": 12 },
        "com.dte.confidence": 0.9,
        "com.dte.source": "stylesheet",
        "com.dte.theme": "light"
      }
    }
  }
}

Top-level keys (always present, empty when no tokens observed): color, typography, spacing, radius, shadow, zIndex, breakpoint, motion.

Exit codes

| Code | Meaning | |------|---------| | 0 | Success | | 1 | User error — bad URL, missing file, invalid flag | | 2 | Extraction failure — timeout, 401/403, DNS, connection refused | | 3 | Internal error |

No partial output file is written on failure (atomic temp + rename).

Current limitations (v1)

• No authentication. Public URLs only. Use --file with a saved rendered HTML for auth-walled sites.
• No source CSS parsing. Token values come from getComputedStyle, which the browser has already resolved. var() chains are pre-resolved before we see them, so the resolve/css-vars.ts module is kept for v2 but unused in v1 output.
• Breakpoints not extracted from live renders. TokenSet.breakpoint is always emitted as {} in v1 — the renderer does not surface stylesheet text, so the @media walker has nothing to consume.
• $metadata.version is hardcoded "0.1.0" instead of being injected from package.json at build time.
• Per-theme slicing — categorizers run once per theme and results are concatenated, rather than the single-pass described in the SDD pseudocode. Output is equivalent; implementation differs.
• Playwright Chromium required. The --fast (static-only) flag is accepted but not implemented in v1 — a warning is printed and the headless renderer is used.

Spec

See the full specification, ADRs, and decisions log at .start/specs/005-design-token-extractor/.

License

MIT