Lighthouse is free, built into Chrome, and checked by millions of people every day. It's also answering a much narrower question than most people assume.
Google Lighthouse is often the first thing people reach for when they want to know "how good is my website." It's fast, free, and built directly into Chrome DevTools — genuinely useful, and worth running. But its scope is narrower than the single number it produces suggests.
| Checks | Lighthouse | AI website audit |
|---|---|---|
| Page load speed | Yes — its core strength | Noted, not the focus |
| Core Web Vitals | Yes | No |
| Accessibility compliance | Yes, automated checks | Partial, contextual |
| Technical best practices | Yes | Partial |
| Message clarity | No | Yes — core focus |
| Trust signal quality | No | Yes |
| Whether copy actually persuades | No | Yes |
| CTA placement & friction | No | Yes |
Everything Lighthouse checks is objectively measurable: how fast pixels paint, whether images have alt text, whether contrast ratios meet a threshold. This is exactly why it's so reliable and consistent — there's no judgement involved, only measurement against a technical standard.
A page can hit 100 on every Lighthouse category and still fail commercially — vague headline, no clear next step, trust signals that exist but sit in the wrong place. None of that is something an automated technical scan can evaluate, because it requires reading and judging content the way a human visitor would, not measuring load timing.
Both tools flag some accessibility and technical-SEO basics — missing alt text, broken heading structure — but even here Lighthouse checks presence while an AI audit can judge whether the structure actually communicates the page's content clearly, which is a meaningfully different bar.
If you suspect a technical performance problem — the site feels slow, or you know Core Web Vitals are failing — start with Lighthouse; it's free, fast, and purpose-built for exactly that. If your site performs fine technically but still isn't converting or ranking the way you'd expect, that's the AI audit's job — it's looking at the questions Lighthouse structurally can't answer.
See what a technical score alone won't tell you.
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