Core Web Vitals Checklist | Web Development Checklist

Measurement Setup

Establish a repeatable performance baseline for important templates.

Record device, network settings, URL, cache state and test time. Compare available real-user measurements with repeated lab tests and identify the affected element or interaction. A single Lighthouse score is a diagnostic observation, not a reliable before-and-after conclusion.

Measure field data where available Critical Strategist Screenshot, report export, URL, test submission, or implementation note
Use PageSpeed Insights and Search Console Critical Strategist Screenshot, report export, URL, test submission, or implementation note
Segment mobile and desktop High Strategist Screenshot, report export, URL, test submission, or implementation note
Identify template-level issues High Strategist Screenshot, report export, URL, test submission, or implementation note
Record LCP, INP, and CLS baselines Recommended Strategist Screenshot, report export, URL, test submission, or implementation note
Prioritize pages with traffic and conversions Recommended Strategist Screenshot, report export, URL, test submission, or implementation note

LCP Improvements

Make the main visible content discoverable and efficient to load.

Identify the actual LCP element before changing assets. Check image dimensions, responsive sources, loading priority and server response, then inspect the request waterfall. Avoid lazy loading the primary image or preloading multiple competing versions that waste bandwidth.

Optimize hero images Critical Marketing Team Screenshot, report export, URL, test submission, or implementation note
Use correctly sized images Critical Marketing Team Screenshot, report export, URL, test submission, or implementation note
Preload critical hero assets when appropriate First confirm the actual LCP asset and its discovery path. Preload only the required responsive resource when testing shows a benefit; duplicate or unnecessary preloads can waste bandwidth. High Marketing Team Screenshot, report export, URL, test submission, or implementation note
Improve server response time High Marketing Team Screenshot, report export, URL, test submission, or implementation note
Reduce render-blocking CSS Recommended Marketing Team Screenshot, report export, URL, test submission, or implementation note
Avoid lazy loading the primary LCP image Inspect the first visible hero image and its network request. It should be discoverable without scrolling or interaction; keep below-the-fold lazy loading where it remains appropriate. Recommended Marketing Team Screenshot, report export, URL, test submission, or implementation note

INP Improvements

Reduce work that blocks real interactions.

Test menu opening, typing, filtering and form submission on a representative mobile device. Identify long tasks and unnecessary script work before delaying dependencies. Retest essential controls and tracking after each change so an improvement in rendering does not break interaction.

Reduce long JavaScript tasks Critical Marketing Team Screenshot, report export, URL, test submission, or implementation note
Delay non-critical third-party scripts Classify dependencies before delaying scripts. Retest navigation, forms, consent controls and conversion recording so a faster audit does not conceal a broken interaction. Critical Marketing Team Screenshot, report export, URL, test submission, or implementation note
Optimize event handlers High Marketing Team Screenshot, report export, URL, test submission, or implementation note
Remove unused JavaScript High Marketing Team Screenshot, report export, URL, test submission, or implementation note
Break up heavy work Recommended Marketing Team Screenshot, report export, URL, test submission, or implementation note
Test real interactions on mobile Recommended Marketing Team Screenshot, report export, URL, test submission, or implementation note

CLS Improvements

Keep the layout stable while resources arrive.

Watch the complete loading sequence, including fonts, consent banners and embedded content. Reserve space for media and avoid inserting late content above what someone is reading. Check slow-load conditions where movement may be more visible than on a warm developer machine.

Reserve image and video dimensions Critical Marketing Team Screenshot, report export, URL, test submission, or implementation note
Avoid injecting content above existing content Critical Marketing Team Screenshot, report export, URL, test submission, or implementation note
Stabilize fonts and layout High Marketing Team Screenshot, report export, URL, test submission, or implementation note
Handle ad or embed spaces carefully High Marketing Team Screenshot, report export, URL, test submission, or implementation note
Avoid late-loading banners pushing content Recommended Marketing Team Screenshot, report export, URL, test submission, or implementation note
Test pages during full load Recommended Marketing Team Screenshot, report export, URL, test submission, or implementation note

Asset and Delivery

Deliver the right assets with verified cache behavior.

Size and compress media for its display, review unnecessary third-party requests and inspect actual cache headers. Confirm CDN and cache rules on ordinary public URLs. A configured optimization option is not evidence that a visitor received the optimized response.

Use compression Critical Marketing Team Screenshot, report export, URL, test submission, or implementation note
Use browser caching Critical Marketing Team Screenshot, report export, URL, test submission, or implementation note
Serve assets through a CDN when appropriate High Marketing Team Screenshot, report export, URL, test submission, or implementation note
Minify CSS and JavaScript High Marketing Team Screenshot, report export, URL, test submission, or implementation note
Audit third-party tags Recommended Marketing Team Screenshot, report export, URL, test submission, or implementation note
Use modern image formats Recommended Marketing Team Screenshot, report export, URL, test submission, or implementation note

Monitoring and QA

Prevent regressions through repeatable acceptance checks.

Retest the same page and device conditions after a change, and compare distributions or repeated runs where practical. Record functional checks alongside performance metrics. Keep performance budgets tied to important templates and user journeys rather than a score target alone.

Retest after fixes Critical Strategist Screenshot, report export, URL, test submission, or implementation note
Track regressions after plugin updates Critical Strategist Screenshot, report export, URL, test submission, or implementation note
Review performance before launches High Strategist Screenshot, report export, URL, test submission, or implementation note
Set a performance budget High Strategist Screenshot, report export, URL, test submission, or implementation note
Monitor high-value pages Recommended Strategist Screenshot, report export, URL, test submission, or implementation note
Document development standards Recommended Strategist Screenshot, report export, URL, test submission, or implementation note

Official References

Use the current documentation for platform-specific settings and requirements.

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