fdl-site-audit

Free, deterministic, zero-dependency website audit library. The same engine that powers the public registry at fivedaylaunch.com/sites.

Audit any website on 5 pillars (100 points total):

Pillar	Max	What it checks
Performance	25	TTFB, page weight, third-party script count
SEO	25	Title, meta description, H1, alt text, noindex
Mobile	20	Viewport tag, responsive readiness
Security	15	HTTPS, mixed content, HSTS
AEO / Modernity	15	JSON-LD, favicon, og:image, og:title

Scored deterministically — no AI inference, no LLM tokens, no API keys, no rate limits, no cost. Average audit takes under a second.

Install

npm install fdl-site-audit

Usage

const { auditUrl } = require('fdl-site-audit');

(async () => {
  const result = await auditUrl('https://example.com');
  console.log(`Score: ${result.score}/100 (Grade ${result.grade})`);
  console.log(`Findings: ${result.findings.length}`);
  result.findings.forEach(f => console.log('  -', f));
})();

Example output

{
  ok: true,
  url: 'https://example.com',
  score: 85,
  grade: 'B',
  grade_label: 'Good',
  breakdown: {
    performance: { score: 10, max: 25, ttfb_ms: 97, page_bytes: 579130 },
    seo: { score: 25, max: 25 },
    mobile: { score: 20, max: 20 },
    security: { score: 15, max: 15 },
    aeo: { score: 15, max: 15 }
  },
  findings: [
    'Heavy page weight (566KB, target <300KB)',
    'Too many third-party scripts (71, recommend <10)'
  ],
  page_bytes: 579130,
  ttfb_ms: 97,
  title: 'Example Title',
  description: 'Example meta description',
  h1: 'Example H1'
}

Grade scale

Score	Grade	Label
90-100	A	Excellent
75-89	B	Good
60-74	C	Average
40-59	D	Below average
0-39	F	Needs work

API

auditUrl(url) → Promise<result>

Run a full audit on a URL. Returns a result object with ok, score, grade, breakdown, findings, and metadata.

If the site blocks automated audits (HTTP 403/406/429 or tiny response body), result.ok is false and result.is_blocked is true.

gradeFromScore(score) → { letter, color, label }

Convert a numeric score (0-100) into a letter grade with display color.

extractChecks(html, headers, url) → object

Pure HTML-to-checks extraction. Useful if you've already fetched the page and just want to score it.

score(checks, ttfb_ms, page_bytes) → { total, breakdown, findings }

Pure scoring function. Useful for testing or rebuilding the scoring logic.

Why this exists

Most SMB website audit tools are either paid ($$$/mo SaaS), gated (Google PageSpeed needs API quotas), or biased toward enterprise concerns. fdl-site-audit is the small-business-first audit:

• Free forever. MIT-licensed, zero dependencies.
• Self-hostable. Works in any Node 18+ environment. No external API calls beyond fetching the target URL itself.
• AEO-aware. Scoring weighs structured data (JSON-LD/schema) for AI-search visibility — most modern audits ignore this.
• No false precision. 5 simple pillars beat 80 obscure metrics. Findings are concrete and actionable.

Used in production by fivedaylaunch.com to audit thousands of small business websites.

Integration ideas

• CI gate: fail your build if your site scores below B.
• Free public tool: spin up a /audit?url=X endpoint in your own app.
• Pre-sales lead-gen: audit a prospect's site before your sales call.
• Sentiment dashboard: track score history for your portfolio of client sites.
• Comparison tool: audit two sites and show side-by-side.

Contributing

PRs welcome. Particularly looking for:

• Additional check primitives (e.g. WebP image detection, lazy-load coverage, font-display checks)
• Performance benchmarks
• Test coverage
• Per-niche scoring presets (e.g. e-commerce vs blog vs SaaS)

License

MIT © 2026 fivedaylaunch.com

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Built by the team at fivedaylaunch.com — we build small business websites in 5 days for $799.