What is the difference between lab and field data?

Lab tests use controlled conditions and are useful for diagnosis. Field data reflects eligible real visits over time and is the better indicator of what users experience.

Will optimisation cause layout shifts or new interaction problems?

Changes are tested with visual stability and responsiveness in mind. I avoid trading a faster headline metric for a worse overall experience.

WordPress service

Core Web Vitals Optimization Service

I review available real-user and lab data, identify issues affecting loading, responsiveness, and visual stability, and prioritise fixes that make sense for the website. I do not promise that every URL will receive an all-green score.

The problem

A single test score does not explain the user experience

Core Web Vitals can vary by template, device, connection, visitor behaviour, and data collection period. Useful optimisation starts by separating loading, interaction, and layout problems and identifying what actually controls them.

What I review on a WordPress site

Available CrUX, Search Console, and lab data
Largest Contentful Paint elements and delivery
Interaction delays and long-running scripts
Layout shifts caused by media, fonts, or embeds
Critical rendering and resource priority
Differences across important page templates

What you receive

Template-level Core Web Vitals assessment
Prioritised LCP, INP, and CLS findings
Agreed fixes and validation tests
Explanation of third-party or platform constraints
Monitoring recommendations for field data

Comparison of real user Chrome field measurements against simulated lab test data for performance analysis — Field data (real Chrome users over 28 days) versus lab data (synthetic Lighthouse tests) in Core Web Vitals optimization.

Process

A clear process from review to handover

01
Gather
Review available field data and test representative pages under controlled conditions.
02
Trace
Identify the resources, scripts, and layout behaviour behind each material issue.
03
Fix
Implement the highest-value changes while protecting functionality and visual stability.
04
Observe
Validate lab results and explain the time needed for field data to reflect changes.

Frequently asked questions

Useful answers before we talk

If your situation is not covered, send the details and I will confirm whether I can help.

No. I can diagnose and improve the factors within the site's control, but field results also depend on visitors, devices, hosting, content, and third-party services.

Discuss your website