How to read PageSpeed Insights (without the noise)

What PageSpeed Insights actually does

PageSpeed Insights runs Google’s Lighthouse tool and shows you a performance report. It simulates loading your page on a device and network, then scores and lists opportunities and diagnostics [1]Source 1 .

The score is useful as a rough health check, but it is not a goal in itself. What matters is whether real users get a fast, stable experience [7]Source 7 .

Which numbers to focus on

Lighthouse reports Core Web Vitals and other metrics. For most small sites, these are the ones that map to what people feel [2]Source 2 .

Largest Contentful Paint (LCP)

LCP measures when the main content (e.g. hero image or big block of text) appears on screen [3]Source 3 .

• Good: Under 2.5 seconds. The page feels like it has “arrived”.
• Needs work: Over 4 seconds. People may assume the site is slow or broken.

Common causes of bad LCP: huge images, slow server, render-blocking CSS or JavaScript, heavy third-party scripts.

Interaction to Next Paint (INP)

INP measures how quickly the page responds to taps and clicks [4]Source 4 .

• Good: Under 200 milliseconds. Clicks and taps feel instant.
• Needs work: Over 500 milliseconds. Buttons and links feel laggy.

Common causes: too much JavaScript running on interaction, heavy scripts blocking the main thread.

Cumulative Layout Shift (CLS)

CLS measures how much the layout jumps while the page loads [5]Source 5 .

• Good: Under 0.1. The page stays stable.
• Needs work: Over 0.25. Content moves and people click the wrong thing or lose their place.

Common causes: images or ads without dimensions, fonts loading and shifting text, content injected above existing content.

What to treat as background noise

• The single overall score: Helpful as a trend, but do not optimise for the number. Optimise for LCP, INP, and CLS on the pages that matter (e.g. homepage, key landing pages, checkout).
• Every “opportunity” as mandatory: Some suggestions have tiny impact. Prioritise fixes that improve LCP, INP, or CLS on real devices.
• Lab vs field: PageSpeed Insights runs in a lab (simulated device and network). For a fuller picture, use Google Search Console’s Core Web Vitals report, which is based on real user data [6]Source 6 .

What to do with the results

1. Pick key pages: Homepage, main service or product pages, and any high-traffic or high-conversion pages.
2. Run PageSpeed Insights on mobile: Use the mobile report; that is where most issues show up and where Google’s index is biased.
3. Note the three numbers: LCP, INP, CLS. If any are in the “Needs work” band, that is your priority.
4. Use the opportunities list: Focus on “Reduce unused JavaScript”, “Properly size images”, “Reduce render-blocking resources” if they appear and map to your worst metric.
5. Fix, then re-test: Make one or two changes, then run the test again. Do not chase a perfect score; chase “good” on the metrics that affect real users.

For more on what “fast” means and how to measure it, see fast websites: what fast means in 2026 and Core Web Vitals for business owners.

Summary

Use PageSpeed Insights to see how your key pages perform on LCP, INP, and CLS. Ignore the noise: one score and every minor suggestion. Prioritise fixes that improve those three metrics, then check real-user data in Search Console when you can.