A website that feels fast on office Wi-Fi can behave differently on a phone. Device capability, signal and the files the page requests all affect the experience. Test the conditions your visitors are likely to face.
Measure the experience, not just a score
Core Web Vitals cover loading, interaction responsiveness and visual stability. The current measures are Largest Contentful Paint (LCP), Interaction to Next Paint (INP) and Cumulative Layout Shift (CLS).
The published “good” thresholds are LCP at or below 2.5 seconds, INP at or below 200 milliseconds and CLS at or below 0.1, evaluated at the 75th percentile of visits. These are useful targets, not a promise that every visit will be identical.
Separate lab tests from real visits
A local Lighthouse run is a controlled diagnostic. Field data describes real visits over time. A site with little traffic may not have enough field data for a public report, and a high lab score does not establish a field result.
Use both where available. Record the page, device settings and date when comparing test runs.
Check the largest downloads first
Look for oversized images, unnecessary video and fonts that delay text. Supply appropriately sized images, reserve their dimensions and avoid loading every gallery image at once.
Review scripts individually. Chat tools, embeds and trackers can add work, but their effect depends on implementation. Measure what is actually loaded rather than assuming every plugin affects every page.
Keep the important content available
The main copy and navigation should not depend on a long sequence of scripts before they appear. Use a sensible font fallback, reduce unnecessary requests and keep the first screen focused.
A static build can simplify delivery, but it can still be slow if it ships heavy assets. Performance is a set of implementation decisions, not a label attached to a platform.
Test what visitors need to do
Open menus, follow service links and complete the form. Watch for jumping layouts and delayed controls. A quick initial load does not compensate for an enquiry route that fails.
Performance checks belong alongside routine website maintenance, particularly after adding integrations or large amounts of content.
Next step: request a free Website Check, or see Baken’s website maintenance plans.