We printed a perfect score and forgot to say which page

On 20 September 2026 we rebuilt our homepage around a small panel that prints the four Lighthouse scores: performance, accessibility, best practices and SEO. All four read 100. It sat next to a screenshot of one of our own pages, and it was meant as evidence that we measure what we build.

A review of it found that it broke a rule we had written for ourselves. Our notes said the numbers had to be labelled with the page, the device and the date. The panel named the device and nothing else.

What the panel said, and what it left out

The panel’s only caption was “measured, mobile, throttled”, and then four 100s. It didn’t say which page had been measured. It didn’t show a date either: the date was in the source code, but nothing on the page displayed it.

A visitor reads a score panel at the top of a homepage as a statement about the homepage. That was the problem, because the homepage no longer scored 100.

What the homepage actually scored

The four numbers had been true of the homepage when we first built the panel. Later that same day we rebuilt the top of the page with the screenshot, and performance dropped to 99. The main content took 2.0 seconds to appear on a throttled phone connection, against 1.7 seconds on pages we hadn’t changed. The panel stayed as it was.

We measured the live homepage several times over two days. It scored 99 every time.

How we nearly explained it away

Runs on our own machine had varied between 94 and 99, and our first reading was noise. Machines do vary, so that isn’t an unreasonable guess, but it was wrong. When we measured the live site and included pages we hadn’t touched as a comparison, the gap was steady: the homepage was always a little behind, and the other pages never were.

A spread of a few points can hide a real difference. The way to tell them apart is a control, a page you didn’t change and measure in the same way, not a shrug. It is the same lesson as measuring in production, not just locally.

We don’t know why the homepage is slower. The image at the top is small, about 10 KB, and it downloads in a fraction of a second. Most of the two seconds is the browser waiting before it paints, not downloading anything. We haven’t found the cause, and we’re not going to pretend we have.

The fix: say what was measured

We had three options. We could find the cause and get the homepage back to 100, but we didn’t know where to look. We could print “99–100”, which makes an exact readout vague and still doesn’t say which page it describes. Or we could make the panel say exactly what it measures. We did the third.

The panel now names the page (/services/web-design, the page in the screenshot beside it), then “mobile, throttled”, then the date, then that page’s real scores. The page, the date and the scores are a single value in the code, and the address bar of the screenshot takes its text from the same value, so the label and the numbers can’t drift apart.

Is the 100 true? We measured that page six times on 21 September. Five runs scored 100. One scored 99, because a single timing, the one Lighthouse calls Speed Index, came out at 3.4 seconds instead of the usual 1.1, while the other timings barely moved. So 100 is that page’s usual score, not a guarantee, and our notes say so.

Checking a score on your own site

If someone shows you a Lighthouse score, these are the questions worth asking:

• Which page? A homepage score says nothing about a checkout or a contact page.
• Phone or desktop, throttled or not? Desktop scores are usually higher, and a phone on a slow connection is what most visitors have.
• When, and on the live site? A developer’s laptop and the real server can give different answers.
• How many runs? Scores wobble from run to run. Ask for several and look at the spread, not the best one.
• Compared with what? Measuring a page you didn’t change tells you whether a change did anything.

What this means for your site

A number with no page, device and date next to it is a decoration. That is how we report figures on our own site now, and how we would on yours. If your site is slow on a phone, or you have a score you can’t trace back to anything, that is what our speed fix is for, and if you need a new site built with this kind of checking from the start, that is our web design service.