What is a Lighthouse score? And why it quietly decides who wins online.
Here's what those numbers mean in plain English, why Google cares about them, and how a website scoring in the high 90s pulls customers away from one that doesn't.
First, the simple version
Lighthouse is a free tool from Google. It grades any website on the internet, including yours and your competitors', and hands it a report card with four scores, each from zero to one hundred.
Anyone can run it in about thirty seconds. Google doesn't rank on the score itself. It measures speed from real visitors instead, and counts that as one of the many signals behind where you land in search results.
Performance
How fast it loads
Accessibility
Can everyone use it
Best Practices
Is it built right and safe
SEO
Can Google find and read it
The same search. Two very different websites.
On the left, a sketch of the shape we usually find on page-builder sites. On the right, a real report from a site we built, which you can go and check. Google sees both.
A typical template site
An illustration, not a measurement: the pattern we keep seeing on Wix, Squarespace, and plugin-heavy WordPress
The Heinrich Firm
Measured on the live site, and published on the case study
That right-hand column is a measured result from one real site, and the case study shows the same numbers. Our mobile Lighthouse performance target is 90+; that is a build standard, not a fleet average. In this example, Performance reads 99, not 100. A clean sweep of four hundreds is rarer than agency marketing suggests, and a page that claims one is usually showing you a desktop run.
Slow sites are common. In data from real visitors, only 48% of mobile sites pass all three of Google's Core Web Vitals. (HTTP Archive, 2024)
What each number means for your business
They're technical, but each one maps directly to customers and revenue.
A low Performance score
A slow site loses customers before they ever see it. Google's own research found 53% of mobile visitors leave a page that takes longer than three seconds to load. If a competitor loads in one second and you load in six, half your visitors are gone before your homepage even appears. (Google (Think with Google), 2017)
A low SEO score
This score checks the basics Google needs to read a page: a title, a description, links it can follow. Passing them won't rank you on its own, but missing them can hold a good page back, and almost nobody clicks past the first handful of results.
A low Accessibility score
It means real customers can't use your site comfortably: someone on a phone in bright sun, an older customer, anyone with a disability. It's also a fast-growing source of lawsuits for small businesses.
A low Best Practices score
This covers security and whether the site sits on solid, current foundations. A low score chips away at the quiet trust a customer needs before they hand over a credit card or fill in a form.
Picture two businesses
Two businesses in the same town offer the same service at similar prices. A customer pulls out their phone and searches for what you both sell.
With everything else that close, speed can be the tiebreaker, and Google puts the faster website first. The customer taps the top result. It loads instantly, looks sharp, and the call button is right there. They call.
The other business, with the slow site three spots down, never even knew that customer existed. That's the kind of customer a slow site loses every day while you're busy running the place.
So why does my site score low?
If your site sits in the 50s and 60s, it's almost certainly not your fault. It's the tools. Most of the low-scoring sites we see are built on page-builders like Wix and Squarespace, or on WordPress weighed down with plugins. They're easy to start with, but they pile on heavy, generic code that browsers and Google have to wade through. Speed is the first casualty.
A website built properly, on a modern foundation, sends the browser a lean, finished page. That's how it lands in the high 90s. If you want the slightly more technical version, here's what we build on and why.
If rebuilding isn't on the table this year, you can still move the scores on the site you already have. That's the whole job in performance optimization: find what's actually slowing the page down and take it out. It's worth doing because the gains show up in sales. Deloitte and Google studied 37 brand sites and found a 0.1-second mobile speed improvement lifted retail conversions 8.4%. (Deloitte and Google, 2020)
Sources
Each source opened and verified · last checked- Google (Think with Google), Find Out How You Stack Up to New Industry Benchmarks for Mobile Page Speed (2017) · 53% of mobile site visitors leave a page that takes longer than three seconds to load, per Google/SOASTA research published by Think with Google in February 2017.
- Deloitte and Google, Milliseconds Make Millions (2020) · A 0.1s mobile speed improvement lifted retail conversions 8.4% and average order value 9.2% across 37 brand sites and 30M+ sessions.
- HTTP Archive, Web Almanac 2024, Performance (2024) · Only 48% of mobile sites pass all three Core Web Vitals; LCP is the weakest metric at a 59% pass rate.
Lighthouse Scores, Answered
Yes, and it's free. The tool is built into Google Chrome, and there are free online versions too. We're also happy to run the full report on your site and walk you through what it means, with no obligation.
Each category is scored 0 to 100. Ninety and above is the green, healthy range and the goal for any serious business website. Most page-builder sites we see sit somewhere in the 50s to 70s, especially on Performance.
Indirectly. Google uses Core Web Vitals from real visitors as one signal among many, not your Lighthouse score. Lighthouse lab-tests two of those vitals and stands in for the third with Total Blocking Time, so a low score usually means real visitors are waiting too.
Almost never. It's usually the tools. Page-builders and plugin-heavy platforms pile on generic, heavy code. A site built properly on a modern foundation sends a lean, finished page, which is how it lands in the high 90s.
Want to know where your site stands?
We'll run the full Lighthouse report on your website for free and show you exactly what it means for your customers, in plain English and with no obligation.