What is page speed?
Page speed is how quickly your page loads its content and becomes usable: not the raw file size, but the experience of waiting. It is measured rather than felt, which is what makes it the least arguable lens: a page is either fast or it is not, and the same tools measure everyone. Google has spent years turning that experience into a small set of named metrics, the Core Web Vitals, so that "it feels slow" can become "your Largest Contentful Paint is 4.1 seconds."
Speed is judged on mobile first, on a mid-range device over an average connection, not on the fast laptop and fibre line the site was built on. That gap is why so many teams are genuinely surprised by their score: the page is quick where they work and slow where their customers actually are.
The Core Web Vitals
Three metrics make up the Core Web Vitals, each capturing a different way a page can feel slow: how long the main content takes to appear, whether the layout stays still, and how quickly the page responds to input. Google publishes the thresholds for "good", so these are targets, not opinions.
| Metric | What it measures | Good |
|---|---|---|
| LCP (Largest Contentful Paint) | How long until the main content is visible | 2.5 seconds or less |
| CLS (Cumulative Layout Shift) | How much the page jumps around as it loads | 0.1 or less |
| INP (Interaction to Next Paint) | How quickly the page responds to a tap or click | 200 milliseconds or less |
Alongside the field vitals, a lab test like Lighthouse reports supporting diagnostics (First Contentful Paint, Speed Index and Total Blocking Time) that help explain why a vital is failing. They are the trail of clues; the vitals are the verdict.
Why slow pages cost you
Speed is not a vanity metric. It shows up on the bottom line through three doors at once.
- Visitors leave. Every second of delay before the page is usable loses some share of the people who arrived, and they leave before they have seen your offer or your proof.
- Rankings suffer. Page experience, Core Web Vitals included, is a signal search engines use. A slow page competes at a disadvantage against a fast one saying the same thing.
- Conversion drops. The same friction that makes a page feel slow makes it feel unreliable, and an unreliable-feeling page converts worse even when everything else is right.
How the audit scores page speed
Page speed is worth 10 of the audit's 100 points, and it is the one lens scored by a third party rather than by us: the audit runs Google PageSpeed Insights against your page on its mobile strategy and reads the Lighthouse Performance result. That Performance score drives the points, and the Core Web Vitals (LCP, CLS, and the supporting lab metrics) become the checklist of findings.
It is weighted at 10 rather than higher on purpose. Speed is real and it matters, but it is also the most solvable problem here (usually a handful of engineering fixes rather than a rethink) and it should not be able to sink a page that is otherwise excellent, or rescue one that is empty but fast.
How to make your page faster
- Fix the biggest image first: compress it, serve modern formats, size it correctly, and make sure the main hero image is not lazy-loaded: it is usually your LCP.
- Reserve space for anything that loads late (images, ads, embeds, fonts) so the layout does not shift and wreck your CLS.
- Cut and defer JavaScript: ship less of it, split it, and stop blocking the main thread while the user is trying to interact: that is what tanks INP.
- Serve assets from a CDN, cache aggressively, and load fonts without blocking render.
- Re-test on mobile after each change, because the score that matters is the one your phone-using customers get, not your laptop.
Frequently asked questions about page speed
What is a good page speed score?
For the Core Web Vitals, aim for Largest Contentful Paint at 2.5 seconds or less, Cumulative Layout Shift at 0.1 or less, and Interaction to Next Paint at 200 milliseconds or less. The audit reads the overall Lighthouse Performance score on mobile, where higher is better.
Why is my site fast for me but slow in the test?
Because the test uses a mid-range mobile device on an average connection, not your fast laptop on fast internet. The gap between where you build and where your customers browse is the whole reason mobile-first measurement exists.
What usually has the biggest impact?
For most sites, the hero image and JavaScript. An oversized or lazy-loaded hero image wrecks LCP, and heavy JavaScript blocks the page from responding. Fixing those two moves the score more than anything else.
How does the free audit measure speed?
It runs Google PageSpeed Insights against your page on the mobile strategy and reads the Lighthouse Performance score, worth 10 points. The Core Web Vitals become the checklist, so you see which metric is dragging you down and by how much.
Get the next post in your inbox
One email when a new post lands — audit patterns, guides and fixes, written like the findings. No filler, unsubscribe any time.