Before/After: Lighthouse scores of real agency sites we rebuilt
Every white-label partner claims to build fast sites. We decided to show the proof. Here are 4 anonymized case studies with real Lighthouse scores — before and after we rebuilt them. No cherry-picking. No tweaked settings. Just the numbers.
Why numbers matter more than promises
As an agency, you hear "we build fast sites" from every freelancer, every white-label partner, every dev shop. It has become meaningless. The only objective proof of site quality is a Lighthouse audit — an open-source tool built into every Chrome browser, measuring exactly what Google measures.
Lighthouse evaluates four categories: Performance (loading speed, interactivity, visual stability), Accessibility (screen readers, contrast, keyboard navigation), Best Practices (HTTPS, console errors, deprecated APIs), and SEO (meta tags, crawlability, mobile-friendliness). A score of 90 or above in each category is considered "good" by Google.
Below are four real projects where agencies came to us with underperforming sites built on WordPress, Wix, or outdated custom code. We rebuilt each one on a modern static stack. Every score shown is from a Lighthouse audit run in Chrome DevTools under default settings — no throttling adjustments, no tricks.
Case 1: SEO Agency — Liege
12-page agency website on WordPress with a premium theme and 8 active plugins. The site served as the agency's main lead generation tool, but load times were hurting their credibility when pitching SEO services to prospects.
| Category | Before | After |
|---|---|---|
| Performance | 34 | 98 |
| Accessibility | 67 | 100 |
| Best Practices | 72 | 100 |
| SEO | 78 | 100 |
Key issues fixed:
- Render-blocking CSS: 3 theme stylesheets loaded on every page, totalling 340KB unminified
- Unoptimized hero image: a 2.4MB PNG served without compression or responsive sizing
- Missing alt tags on 23 of 31 images across the site
- No schema markup — the SEO agency's own site had zero structured data
- jQuery + 8 plugin scripts loaded globally, adding 1.1MB of JavaScript to every page
Stack: Next.js 14, Tailwind CSS, static export, deployed on Netlify | Timeline: 8 working days
Case 2: Marketing Agency — Brussels
6-page site built by a former intern two years prior. No responsive design, no SEO considerations, no HTTPS. The agency had been embarrassed to share their own URL with prospective clients.
| Category | Before | After |
|---|---|---|
| Performance | 41 | 96 |
| Accessibility | 52 | 98 |
| Best Practices | 58 | 100 |
| SEO | 61 | 100 |
Key issues fixed:
- No viewport meta tag — the site was completely unresponsive on mobile devices
- Images served as full-size PNGs (largest: 3.8MB), no compression, no lazy loading
- Inline styles on nearly every element, making maintenance and consistency impossible
- No heading hierarchy — multiple H1 tags per page, skipped heading levels throughout
- No HTTPS certificate and mixed HTTP/HTTPS content loading
Stack: Next.js 14, Tailwind CSS, static export, deployed on Vercel | Timeline: 6 working days
Case 3: Design Studio — Namur
Portfolio site on Wix showcasing the studio's work. Beautiful designs trapped inside a platform that gave them zero control over HTML output, load performance, or technical SEO.
| Category | Before | After |
|---|---|---|
| Performance | 28 | 99 |
| Accessibility | 71 | 100 |
| Best Practices | 67 | 100 |
| SEO | 82 | 100 |
Key issues fixed:
- Wix runtime JavaScript: 800KB+ of platform JS loaded before any page content appeared
- No lazy loading — all portfolio images (42 total) loaded simultaneously on page visit
- Inaccessible navigation — keyboard users could not tab through the mobile menu
- Auto-generated HTML bloat — Wix produced deeply nested divs with cryptic class names, making the DOM 3x larger than necessary
Stack: Next.js 14, Tailwind CSS, static export, deployed on Cloudflare Pages | Timeline: 7 working days
Case 4: Accounting firm — Luxembourg
4-page site built with WordPress + Elementor. The firm's managing partner had complained about the site being "painfully slow" for over a year. Their previous developer had tried caching plugins without success.
| Category | Before | After |
|---|---|---|
| Performance | 22 | 97 |
| Accessibility | 59 | 100 |
| Best Practices | 65 | 100 |
| SEO | 71 | 100 |
Key issues fixed:
- Elementor CSS and JS: 1.2MB of page builder assets loaded on every page, most unused
- Four font families loaded (only one was actually used in the design), adding 600KB
- No caching headers configured — every asset was re-downloaded on every visit
- No semantic HTML — all content wrapped in generic divs, no landmarks or ARIA labels
- Cumulative Layout Shift (CLS) of 0.42 due to images and ads loading without defined dimensions
Stack: Next.js 14, Tailwind CSS, static export, deployed on Netlify | Timeline: 5 working days
What these numbers mean for your clients
Across these four projects, the average improvement was +63 points in Performance and +37 points in Accessibility. Every site went from "poor" or "needs improvement" to "good" or "excellent" across all four Lighthouse categories.
But Lighthouse scores are not just vanity metrics. They translate directly into business outcomes:
Lower bounce rate. Google research shows that as page load time goes from 1s to 3s, bounce probability increases by 32%. From 1s to 5s, it increases by 90%. Every second matters.
Better SEO rankings. Core Web Vitals (Performance metrics within Lighthouse) are confirmed Google ranking signals since 2021. Sites scoring 90+ consistently outrank slower competitors for equivalent content.
Improved conversions. A 1-second improvement in load time increases conversions by an average of 7% (Deloitte study). For a site generating 50 leads per month, that is 3-4 additional leads — every month.
The pattern across all four case studies is clear: most performance and accessibility issues are stack-related, not content-related. The agencies had good content, good designs, and clear messaging. Their technology was holding them back. Swapping the stack — without changing the design or content — unlocked scores that were previously impossible.
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