Website Performance

A slow website loses visitors before it even loads. Every extra second of waiting hurts conversion, damages Google rankings and gives an impression of neglect. Performance isn’t technical vanity — it’s user experience and business results.

At Monto IA, performance is part of the product from day one, not a last-minute fix. We build with a focus on fast loading, visual stability and accessibility — and we measure everything with real tools.

What’s included

• Core Web Vitals: optimization and monitoring of LCP (loading), CLS (visual stability) and INP (interaction response) — the metrics Google uses for ranking
• Optimized images: modern formats (WebP/AVIF), responsive sizing and on-demand loading (lazy loading)
• Lean delivery: minimal CSS and JavaScript, no unnecessary heavy frameworks — only what the page actually needs
• CDN and cache: global distribution via Cloudflare, with caching configured to serve every visitor from the nearest location
• Accessibility: contrast, keyboard navigation and correct semantics — a fast website everyone can use

Why it matters

• Conversion: pages that load within 2s convert far more than those taking over 5s
• SEO: since 2021 Google uses Core Web Vitals as a ranking factor
• Media cost: in Ads campaigns, fast pages improve quality score and reduce cost per click

Lighthouse report

Lighthouse is Google’s tool that audits performance, accessibility, best practices and SEO. This is how we deliver our websites — every score in the green, on mobile and desktop.

The performance score is the only one that doesn’t depend entirely on us: even in a controlled lab test (simulated network and CPU), results vary run to run for factors outside our control — load on Google’s test server at that moment, latency to it, network noise. And in real life, each visitor’s experience also varies with their device and connection. That’s why we guarantee performance from 90 up — Google’s first green band — while accessibility, best practices and SEO, which depend only on the development, we deliver at 100.

A score in the green isn’t luck: it’s the result of technical decisions made throughout the entire project. And more important than the number is the real experience of every visitor — a website that opens fast on any connection.

Lighthouse vs. PageSpeed Insights: what’s the difference?

Both tools share the same engine — PageSpeed Insights (PSI) runs Lighthouse under the hood and uses the same four categories (performance, accessibility, best practices and SEO). The difference is in the kind of data each one shows:

• Lighthouse (Chrome DevTools, extension or CLI): only lab data — a simulated test, in a controlled environment, with network and CPU artificially throttled to reproduce a mid-range phone. This is what we run during development, since it’s repeatable and doesn’t depend on real traffic to the site.
• PageSpeed Insights: shows the same lab test and adds field data — real metrics collected from actual visitors to the site over the last 28 days, via CrUX (Chrome User Experience Report, Chrome’s own aggregated telemetry). That’s why PSI has two separate sections: “Field data” (what your real visitors experienced) and “Lab data” (the simulated test, the same number Lighthouse would show).

In practice: Lighthouse (and PSI’s “lab” tab) measures the site under controlled conditions — that’s what we guarantee contractually. PSI’s “field data” reflects the real diversity of visitors — device, connection, region — and is shaped by factors no developer controls alone.

W3C validation: why error-free code matters

The W3C (World Wide Web Consortium) is the international body that defines web standards — the rules for how HTML and CSS should be written to behave predictably across any browser, screen reader or search engine. The W3C Markup Validator checks whether a page’s HTML follows those rules.

Our sites go through this check on every build — it’s not just talk: an automated gate blocks publishing if the generated HTML has errors equivalent to those flagged by the W3C validator. Some of what’s checked:

• Duplicate IDs: every id must be unique on the page — duplicated, it breaks anchor links, form labels (label for) and JavaScript element lookups
• Correct element nesting: the spec defines what each tag may contain (a <div>, for instance, can’t sit inside a <button> or a paragraph)
• A single <main> per page, tags closed in the right order, and correct handling of special characters (like &) in visible text

Worth a caveat: W3C validation is not the same as accessibility. Valid markup is a prerequisite for accessibility, but the accessibility standard itself (WCAG) is a separate rule set — it’s what Lighthouse audits separately under the “Accessibility” score.

The benefit: less recovery work for the browser, more consistency for visitors

Modern browsers follow an error-recovery specification (the HTML5 parsing algorithm): faced with malformed markup, they don’t crash or “guess” randomly — they apply deterministic rules to patch the structure behind the scenes. But that recovery has real cost and side effects:

• Extra processing: the browser spends additional cycles rebuilding the document tree instead of just parsing what was already correct
• Unpredictable final structure: the browser’s “fixed” HTML can end up different from what was written — breaking CSS selectors, JavaScript lookups and the structure screen readers rely on
• Inconsistency across tools: browsers, search crawlers, screen readers and link-preview services (social sharing) don’t always fix the same error the same way — valid HTML guarantees every one of them “reads” the page identically

The performance gain here is real, but indirect and secondary: clean code removes that recovery overhead and avoids reflows caused by an unexpected tree. What still weighs most on the performance score is what we already covered above — image weight, JavaScript and CSS shipped, server response time. Valid HTML doesn’t turn a slow site fast on its own; it removes silent friction that undermines cross-browser consistency, accessibility and maintainability — and protects the performance already built.