What Is a Good Lighthouse Score? (And What to Do If Yours Is Bad)

So you ran a Lighthouse audit. You got a bunch of numbers between 0 and 100, some red, some orange, maybe a couple in green. And now you're staring at the screen wondering what any of it means and whether you should be worried.

I get it. I've looked at hundreds of these reports with business owners who felt the same way. The good news is that once you understand what the scores actually measure, the whole thing becomes a lot less intimidating.

Let me walk you through it in plain English.

What Is Google Lighthouse?

Google Lighthouse is a free, open-source auditing tool built into Chrome. It loads your website in a simulated browser, runs a series of tests, and produces a report with scores across four categories. You can run it yourself from Chrome's DevTools (right-click your page, select Inspect, click the Lighthouse tab), or you can use Google's PageSpeed Insights which runs Lighthouse for you and adds some extra data from real Chrome users.

Lighthouse is not a Google ranking factor on its own. But the things it measures (how fast your site loads, whether it's usable on mobile, whether it's accessible to people with disabilities) do affect how people experience your site, and Google does care about that. If you want the full picture on how Google measures real-world speed, I've written a separate guide on Core Web Vitals that goes deeper into the specific metrics Google uses.

For now, the key point is this: Lighthouse gives you a structured way to understand what's working and what's broken on your website. It's a diagnostic tool, not a pass-or-fail exam.

The Four Categories, Explained

Lighthouse scores your site across four categories. Each one gets a number from 0 to 100.

Performance

This is the one most people fixate on, and it's usually the one that looks the worst. Performance measures how fast your page loads and becomes usable. Lighthouse looks at things like:

• How long until the first bit of content appears on screen (First Contentful Paint)
• How long until the largest element (usually a hero image or headline) finishes loading (Largest Contentful Paint)
• How long until the page is mostly interactive and responds to clicks (Time to Interactive)
• How much the layout shifts around while loading (Cumulative Layout Shift)

These are the same metrics Google uses for Core Web Vitals, so improving your Performance score generally improves your real-world speed too. I've seen sites where shaving 1.5 seconds off load time improved mobile conversion rates by 15% or more. Speed directly affects whether people stay or leave. I wrote about this in more detail in how slow websites lose customers.

Accessibility

Accessibility measures whether your site is usable by people with disabilities. That includes people using screen readers, people who can't use a mouse and navigate by keyboard, people with colour blindness, and people with low vision who need to zoom.

Lighthouse checks things like:

• Do your images have alt text describing what they show?
• Do your form fields have proper labels?
• Is there enough contrast between text and background colours?
• Can you navigate the page using only the Tab key?

A low Accessibility score means you're potentially locking out customers and, depending on where you operate, you may have legal exposure under accessibility regulations like the UK's Equality Act 2010 or the Americans with Disabilities Act. I've seen plenty of sites scoring 60 or 70 here when simple fixes (adding alt text, fixing colour contrast) would push them to 90+.

Best Practices

This category checks whether your site follows general web development good practices. It looks at things like:

• Are you using outdated or insecure protocols (HTTP instead of HTTPS)?
• Are there console errors in your JavaScript?
• Are your images sized appropriately for the screen?
• Are you using deprecated APIs that browsers will eventually stop supporting?

Best Practices is usually the easiest category to get a high score in. If you're on HTTPS and your site isn't throwing JavaScript errors, you're probably already in the green. But if you're seeing a low score here, it often points to underlying problems that will eventually cause bigger issues if left alone.

SEO

SEO checks whether your site is discoverable and indexable by search engines. Lighthouse looks at things like:

• Does your page have a meta description?
• Is the page title descriptive?
• Are links crawlable?
• Does your robots.txt block important pages?
• Is the font size large enough to be readable on mobile?

A low SEO score usually means you're making it harder for Google to understand and rank your page. These are basic on-page optimisation factors. Fixing them won't magically put you at the top of Google, but ignoring them can hold you back. A lot of the issues that show up here overlap with the problems I cover in common website mistakes businesses make.

What Do the Colours Mean?

Each category score gets a colour, and the colour matters as much as the number. Lighthouse uses a traffic light system:

• 0 to 49: Red (Poor). This means there are real problems. A red Performance score means your site is slow enough that visitors are probably leaving. A red Accessibility score means people with disabilities likely can't use your site properly. You should prioritise fixing these.
• 50 to 89: Orange (Needs Improvement). Your site is functional but not great. There are specific issues you should address, but you're not in crisis mode. Most small business websites sit in this range, especially on mobile Performance.
• 90 to 100: Green (Good). Your site is in good shape for this category. You can stop worrying about it and focus your attention elsewhere.

The colour bands are the same for all four categories. A 90 in Performance is green. A 90 in Accessibility is green. The thresholds don't change.

One thing to keep in mind: a 90 and a 100 are both green. The difference between them is much smaller than the difference between an 85 and a 92. Don't obsess over the exact number once you're in the green.

Lab Data vs Field Data: What's the Difference?

This is one of the most confusing parts of a Lighthouse report, and it trips up nearly everyone I talk to.

When you run Lighthouse through Chrome DevTools or through PageSpeed Insights, the scores come from lab data. That means Lighthouse loads your page in a simulated environment with a simulated mobile device, a simulated network connection, and a simulated CPU. It runs the test the same way every time so you get consistent, repeatable results. Lab data is good for diagnosing problems because it's controlled and predictable.

But lab data is not the same as what your actual visitors experience. Real visitors use different phones, different network speeds, different browsers. Some are on fibre broadband. Some are on a creaky 3G connection on a train. Their experience varies.

That's where field data comes in. If you use PageSpeed Insights, you'll see a separate section (usually below the Lighthouse scores) labelled "Origin" or "Field Data." This comes from Google's Chrome User Experience Report (CrUX). It's data collected from real Chrome users who visited your site over the previous 28 days. It shows the actual Largest Contentful Paint, Cumulative Layout Shift, and First Input Delay that real people experienced.

Here's the important bit: your Lighthouse lab score can be 95, but your CrUX field data might show something worse, because real users on slow phones over slow connections have a harder time than Lighthouse's simulated test. Both numbers matter. Lab data helps you diagnose and fix problems. Field data tells you what's actually happening to your visitors.

If your Lighthouse score is green but your field data is orange or red, it usually means your site works fine on fast devices but struggles on slower ones. The fix is the same either way: make the page load less stuff and load it faster.

"My Desktop Score Is 95 But Mobile Is 40. Why?"

I hear this one all the time. Here's what's happening.

When Lighthouse runs a desktop audit, it simulates a fast desktop computer on a fast network. Your site probably loads fine under those conditions because it was likely built and tested on a desktop machine by someone sitting at a desk with good broadband.

When Lighthouse runs a mobile audit, it simulates a mid-range mobile phone on a throttled 4G connection. The CPU is slower. The network is slower. Everything takes longer. Images that loaded instantly on desktop now take 3 seconds. JavaScript that ran in 200 milliseconds on desktop takes 800 milliseconds on mobile. Layout shifts that were barely noticeable on a large monitor become jarring on a small screen.

Most websites are built desktop-first, even in 2026. Developers test on their laptops, everything looks great, and nobody checks mobile until the client runs a Lighthouse audit and panics.

The gap between desktop and mobile scores is completely normal. But it's also a sign that your site needs mobile-specific optimisation. Compressing images, reducing JavaScript, using responsive layouts that don't load desktop-sized assets on phones, and deferring non-essential scripts can all close that gap significantly.

I've taken sites from a mobile Performance score of 35 to 90+ by doing exactly those things. It's not magic, it's just cleaning up the stuff that shouldn't have been loading on mobile in the first place.

Do You Need a Perfect 100?

No. And I say that as someone who used to chase 100s when I first started running audits.

Here's the reality. Going from a 50 to a 90 is a meaningful improvement that your visitors will notice. Going from a 90 to a 100 is increasingly difficult with diminishing returns. The last 10 points often require trade-offs that don't make sense for a small business website. You might need to strip out functionality your customers actually use, or spend hours optimising something that saves 50 milliseconds.

Google itself says a score of 90 or above is "good." That's the target I recommend to my clients. If you're at 90 or above in Performance and Accessibility, you're in good shape. Focus your energy on other things: your content, your actual business, your customers.

The exception is if your score is sitting at 88 or 89 and you can see a specific, simple fix that would push you over 90. In that case, do it. But don't spend a week chasing a 100 when you've got a business to run.

What to Fix First

If you've got red or orange scores across multiple categories, it's tempting to try and fix everything at once. Don't. Prioritise.

1. Fix Performance first if it's red. A slow site drives visitors away before they can read your content, buy your product, or contact you. Nothing else matters if people leave before the page loads. Start with image optimisation (compress them, serve them in modern formats like WebP, size them properly for the screen) and removing unnecessary third-party scripts.
2. Fix Accessibility next. Many accessibility fixes are quick: add alt text to images, ensure form fields have labels, check your colour contrast. These changes make your site usable by more people and reduce legal risk.
3. Then look at SEO and Best Practices. These are usually lower effort. Add a meta description, fix console errors, make sure you're on HTTPS. Most of these take minutes.

If you want a deeper look at the kinds of issues that drag scores down, I wrote about common website mistakes businesses make which covers the problems I see most often.

A Quick Note on Running the Audit

If you're running Lighthouse yourself, run it in an incognito window with no browser extensions. Extensions can interfere with the results and give you inaccurate scores. Run it a couple of times and take the average, because scores can vary slightly between runs depending on network conditions and how your server responds.

And always test the mobile version. That's the one Google cares about most for ranking, and it's the one your customers are most likely to see. Over 60% of web traffic in 2026 comes from mobile devices. If your mobile experience is poor, that's where to focus.

What to Do If Your Score Is Bad

If you've run the audit and you're sitting in the red or orange, don't panic. Bad scores are fixable. I've seen sites go from a mobile Performance score of 25 to 92 in a single round of fixes.

The challenge for most small business owners is that the Lighthouse report tells you what's wrong but not how to fix it in terms a non-developer can understand. It says things like "Eliminate render-blocking resources" and "Reduce JavaScript execution time" and "Serve images in next-gen formats." If you don't know what render-blocking resources are, that's not very helpful.

That's exactly why I started WL Tech. I spent over a decade as a sysadmin and DevOps engineer fixing infrastructure problems for large organisations. Now I help small businesses understand and fix their websites without the jargon and without the agency price tag.

If you've run a Lighthouse audit and you're not sure what to do next, I'll run a full audit for free at wltech.pro. I'll translate the report into plain English, tell you exactly what's dragging your scores down, and explain what it would take to fix them. No obligation, no sales pitch. If you want to go further, I offer a detailed Developer Report for $150, a Quick Fix for $250, and a Full Fix starting at $500 depending on what your site needs.

Run your audit, have a look at your scores, and if you want someone to help you make sense of it, you know where to find me.