Field note · Website performance · · 3 min read
Use Core Web Vitals to investigate customer friction
A visitor taps the enquiry button and waits. They tap again because the page has not responded. Your analytics may record a visit without an enquiry, but that alone will not explain what happened. Performance measurements can help identify whether the interface got in the way.
Core Web Vitals describe three parts of that experience. Google's Web Vitals guidance gives each measurement a good threshold. At least 75% of measured visits should meet it, assessed separately for mobile and desktop. A single fast test on an office connection is not enough to establish that visitors have a good experience.
What the measurements describe
Loading: LCP
Largest Contentful Paint measures when the largest visible content element appears. Example: a visitor waits for the main image or headline.
Response: INP
Interaction to Next Paint measures responsiveness to interactions. Example: the page gives no visible response after a visitor taps a button.
Stability: CLS
Cumulative Layout Shift measures unexpected movement. Example: content appears above a form and moves the control the visitor was about to use.
Layout shifts can occur while someone uses the page, as well as during its initial load. A banner or late-loading component can move content after the visitor has started interacting. Reserving the correct space for that content can prevent a particular shift; the measurement helps the team find where to look.
Read a change against the customer journey
Suppose mobile responsiveness gets worse after a release and fewer visitors complete the enquiry form. That is a reason to investigate the form on affected devices. It is not yet evidence that response time caused the drop. The same release might have changed validation, and the marketing team might have changed where visits come from.
A useful report puts the performance change beside the relevant customer action and the release date. Keep the page group, device category, and measurement window visible. Ask whether enough real-visitor data is available before drawing a conclusion. Controlled tests can then help reproduce a problem that field measurements suggest.
Google says its ranking systems use Core Web Vitals, but meeting the targets does not guarantee a high search position. A strong performance score also cannot establish whether your offer is persuasive. These measurements answer a narrower question about how the page behaves.
Give the report an owner
Assign someone to review material changes after releases and decide what needs investigation. For each finding, record the affected page, the observed behavior, and the proposed correction. After the fix, check that the behavior improved, then watch the field data over its reporting window.
For the enquiry page, the useful result is a form that responds when a visitor acts, with evidence that the correction holds for the devices people use. Keep enquiry completion and lead quality beside the performance measures so the team can see whether the broader journey also improved.
Written by the Moga principals.