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The Lighthouse Audit Checklist: 50 Points We Check on Every Site

A comprehensive Lighthouse audit checklist — performance, accessibility, best practices, SEO. The 50-point list we run on every web performance engagement.

Wadhah Belhassen2027-01-0113 min read

A Lighthouse audit checklist is only useful when applied with discipline. Most teams open Lighthouse, see a yellow Performance score, and stop. The real audit covers performance, accessibility, best practices, SEO, and PWA dimensions — each one packed with specific issues that compound into the visible scores.

This is the 50-point Lighthouse audit checklist we run on every web performance engagement. It covers each Lighthouse category in depth, with the specific fixes that move scores most reliably. By the end you will know exactly which levers to pull on your own site.

The checklist is grouped into five sections — Performance, Accessibility, Best Practices, SEO, and PWA. Work through them in order. Out-of-order optimisation wastes weeks.

Section 1 — Performance (15 points)

Performance is the most-discussed Lighthouse category, with the most leverage for conversion impact.

1. Is mobile LCP under 2.5 seconds?

The single most important Core Web Vital. Below 2.5 seconds is "good", above 4 seconds is "poor". We covered the LCP mechanics in our Core Web Vitals deep dive guide.

2. Is mobile INP under 200 milliseconds?

Replaced FID in 2024. Measures the worst interaction delay in the session. Above 500 ms feels noticeably sluggish.

3. Is CLS under 0.1?

Cumulative Layout Shift. Above 0.25 is poor. Common cause: images without dimensions, late-loading ads, font swap shifts.

4. Is TTFB under 600 ms?

Time to First Byte from server. Above 800 ms means front-end optimization cannot save you. Check hosting.

5. Are images served in modern formats (WebP, AVIF)?

JPEG and PNG ship 25 to 60 percent more bytes than necessary. Convert. We covered the formats in our image optimization guide.

6. Are images properly sized for their display dimensions?

A 4,000 x 2,000 image displayed at 1,200 x 600 wastes bytes. Use srcset with appropriate sizes.

7. Is the LCP image marked with `fetchpriority="high"`?

Free 200 to 800 ms LCP improvement. Most sites do not set this.

8. Are below-the-fold images lazy-loaded?

loading="lazy" on all non-critical images. Default in 2026 but often missed.

9. Is JavaScript bundle under 200 KB compressed for marketing pages?

For interactive apps, 400 KB max. Above that, audit and reduce. We covered the patterns in our JavaScript performance optimization guide.

10. Are non-critical scripts deferred?

defer attribute, lazyOnload strategy, or Partytown. Synchronous third-party scripts are the biggest performance killer.

11. Is critical CSS inlined?

Above-the-fold CSS in the <head> inline. Non-critical CSS loaded async.

12. Are web fonts using `font-display: swap`?

Prevents FOIT. Plus metric-matched fallback to prevent CLS. We covered this in our web fonts performance guide.

13. Are static assets cached with `max-age=31536000, immutable`?

For hashed-filename assets, year-long caching. Browser cache eliminates repeat-visit network requests.

14. Is HTTP/2 or HTTP/3 enabled?

Multiplexed connections. Standard on modern hosting.

15. Is Brotli compression enabled?

20 to 30 percent smaller than gzip. Most CDNs support out of the box.

Section 2 — Accessibility (10 points)

Accessibility affects both Lighthouse score and real users with disabilities.

16. Do all images have `alt` attributes?

Required for screen readers. Empty alt="" is acceptable for decorative images.

17. Do all form fields have associated labels?

<label for="..."> or aria-label on every input.

18. Is colour contrast at least 4.5:1 for body text?

WCAG AA minimum. Lighthouse flags low-contrast text.

19. Are heading levels logically structured?

<h1> once, then <h2> for sections, <h3> for subsections. Skipping levels confuses screen readers.

20. Are interactive elements keyboard-accessible?

Tab navigation works. Focus indicators visible. No keyboard traps.

21. Are link names descriptive?

"Click here" fails. "Read our Google Ads case study" works.

22. Is the language declared on `<html>`?

<html lang="en"> (or fr, ar, etc.). Critical for screen readers and translation tools.

23. Are ARIA roles used correctly?

If used, must be valid roles applied to appropriate elements. Misused ARIA hurts accessibility.

24. Are skip-to-content links provided?

Allow keyboard users to skip past navigation to main content.

25. Are video and audio captions provided?

For users with hearing impairments and SEO.

Section 3 — Best Practices (8 points)

Lighthouse's catch-all category for security and reliability.

26. Is HTTPS enforced site-wide?

Plain HTTP triggers browser warnings. Redirect to HTTPS at the server or CDN.

27. Are JavaScript errors absent from the console?

Production should have zero JavaScript errors. Each one represents broken functionality somewhere.

28. Are deprecated APIs absent?

document.write(), synchronous XHR, old web platform features. Replace with modern equivalents.

29. Are third-party cookies handled appropriately?

GDPR compliance for European audiences. Cookie consent banners that actually block tracking until accepted.

30. Is Content Security Policy (CSP) configured?

Restricts what scripts and resources can load. Reduces XSS attack surface.

31. Are HTTP headers configured securely?

Strict-Transport-Security, X-Content-Type-Options, X-Frame-Options, Referrer-Policy.

32. Is the doctype set to HTML5?

<!DOCTYPE html>. Missing doctype causes browser quirks.

33. Are images displayed with proper aspect ratio?

Width and height attributes or aspect-ratio CSS. Prevents CLS and distortion.

Section 4 — SEO (10 points)

The Lighthouse SEO category covers technical SEO basics.

34. Is there a `<title>` element under 60 characters?

Required. Should be unique per page. Affects search result CTR.

35. Is there a meta description under 160 characters?

Not a ranking factor but affects CTR. Should be unique per page.

36. Are headings present and structured?

At least one <h1>. Hierarchical use of <h2>, <h3>, etc.

37. Is the viewport meta tag present?

<meta name="viewport" content="width=device-width, initial-scale=1">. Required for mobile rendering.

38. Is the robots.txt valid?

Allows search engines to crawl appropriate pages. Blocks admin and duplicate paths.

39. Is structured data (schema markup) valid?

LocalBusiness, Service, FAQPage, BreadcrumbList where appropriate. We covered the schema patterns in our local schema markup guide.

40. Are canonical URLs declared?

<link rel="canonical" href="..."> to prevent duplicate content issues.

41. Are hreflang tags set for multilingual sites?

<link rel="alternate" hreflang="..."> for each language version. Critical for international SEO.

42. Is the sitemap.xml accessible?

/sitemap.xml listing all indexable pages. Submitted to Search Console.

43. Are pages mobile-friendly?

Responsive design, no horizontal scrolling, tap targets at least 44x44 pixels.

Section 5 — Progressive Web App (7 points)

PWA criteria. Not relevant for every site but worth addressing for installable apps.

44. Is there a web app manifest?

/manifest.webmanifest with name, icons, theme color, display mode.

45. Is a service worker registered?

For caching and offline functionality.

46. Is the site installable?

Manifest valid, service worker registered, HTTPS, icon present.

47. Does the site work offline?

Service worker caches critical resources. App shell loads without network.

48. Does the splash screen appear correctly?

Theme color, background color, name properly set in manifest.

49. Are icons provided in multiple sizes?

192x192 and 512x512 minimum. Plus apple-touch-icon for iOS.

50. Is the start URL configured?

Manifest start_url set to the right landing page for app launches.

How to score the audit

Count how many of the 50 points you pass. Most sites we audit pass 22 to 32 points. Strong accounts pass 42+.

Each missed point matters at different levels:

Performance: directly affects conversion and SEO
Accessibility: affects real users, legal compliance, search ranking
Best Practices: security and reliability
SEO: search engine visibility
PWA: only matters for installable apps

Prioritise based on what affects your business.

A 30-day plan to fix the worst leaks

Run the audit. Then attack the gaps in this order.

Days 1 to 7 — Performance. Image formats, JS bundle reduction, deferred scripts, font display. Highest business impact.

Days 8 to 14 — Accessibility. Alt text, form labels, color contrast, keyboard navigation.

Days 15 to 19 — SEO. Titles, descriptions, headings, structured data, canonical URLs.

Days 20 to 24 — Best Practices. HTTPS, security headers, deprecated APIs, JavaScript errors.

Days 25 to 28 — PWA (if relevant). Manifest, service worker, offline support.

Days 29 to 30 — Re-audit. Compare to baseline. Most sites move from "yellow" to "green" across all categories.

Common Lighthouse mistakes

These are the patterns we see most often.

Optimising lab score, ignoring field data. Lab data is synthetic. Real user experience comes from CrUX field data.

Chasing perfect 100 scores. Lighthouse score is not the goal. Real-world Core Web Vitals on real users is.

Ignoring accessibility because the site "works fine". It works fine for you. Users with disabilities face barriers.

Skipping SEO basics on developer-focused sites. Title, description, schema affect every site, not just marketing sites.

Running Lighthouse on desktop only. Mobile scores matter more. Most traffic is mobile.

Trusting Lighthouse over real performance monitoring. Lighthouse is a starting point. RUM (real user monitoring) is the source of truth.

How Lighthouse fits into the broader stack

Lighthouse is one tool. The full performance stack includes:

Lighthouse: lab audits for development
PageSpeed Insights: lab + field data, Google's official tool
Chrome DevTools: detailed debugging
Web Vitals JS library: real user monitoring on your site
Vercel Speed Insights / SpeedCurve / New Relic: production RUM dashboards
Bundle analyzers: per-build JS analysis

Lighthouse is the entry point. Use it to find issues. Use the other tools to validate fixes in production.

A real example — Marseille cosmetics Lighthouse audit

We took over a Marseille cosmetics e-commerce site scoring 28/100 on Performance, 76/100 on Accessibility, 84/100 on Best Practices, 71/100 on SEO.

After 45 days of the framework above — image optimization, JS bundle reduction, deferred third-party scripts, alt text everywhere, schema markup, security headers — scores improved to: Performance 96/100, Accessibility 100/100, Best Practices 100/100, SEO 100/100.

More importantly: real-user Core Web Vitals all moved into "good" range. Conversion rate lifted 31 percent in the following 60 days. The full story is in our Marseille cosmetics case study.

Frequently asked questions

What's a good Lighthouse Performance score?

90+ is "good". 50 to 89 is "needs improvement". Below 50 is "poor". Aim for 90+ on production. Above 95 has diminishing returns.

How often should I run Lighthouse?

Once per major release minimum. Monthly for stable sites. Before every deploy is ideal for performance-critical sites.

Should I use the Lighthouse extension or PSI?

PageSpeed Insights uses Google's servers and includes field data. Lighthouse extension runs locally. Both have value — PSI for measurement, extension for debugging.

Why does my Lighthouse score vary between runs?

Lab tests have variance. Run 3 to 5 times and take the median. Big variance suggests network or device throttling inconsistency.

Can I improve Lighthouse without a developer?

For managed platforms (Shopify, Squarespace, modern WordPress), most improvements are configuration changes. For custom sites, developer involvement is usually needed for deep optimization.

Does Lighthouse score affect SEO?

Lighthouse Performance correlates with Core Web Vitals, which are ranking factors. SEO category covers technical SEO basics. Accessibility affects user experience signals.

Get a Lighthouse audit

We run this exact 50-point audit on sites free of charge. Within 48 hours we deliver a scored breakdown and prioritised action plan ranked by expected impact on Core Web Vitals and conversion.

Book a free 30-minute audit. We screen-share, walk through your Lighthouse and CrUX data, and you leave with a clear action plan.

Or explore our Web Development service for the full system we run on performance-focused client accounts.

Want these strategies applied to your business?

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