Before you start
- A verified Search Console property (URL prefix) for the site you are tuning.
- Staging or off-peak window if you will change caching, themes, or ad tags.
Separate lab vs field data
Lighthouse in Chrome is synthetic; Search Console shows aggregated field data from real users (when thresholds are met).
Prioritize URLs that fail in the field report — that is where revenue and rankings quietly leak.
LCP: hero image, fonts, and server TTFB
Identify the LCP element in DevTools Performance recording on a cold load — often a hero image or large heading block.
Serve responsive sizes, avoid loading a 4000px asset into a 800px slot, and consider fetchpriority="high" only for the true hero (not every image).
Reduce webfont weight: fewer families/weights, font-display: swap or optional, and subset if your license allows.
INP: interactions blocked by long JS tasks
Heavy page builders, tag managers, chat widgets, and poorly written sliders inflate interaction delays.
Defer non-critical scripts, lazy-load embeds below the fold, and test logged-out vs logged-in because admin bars skew measurements.
CLS: reserve space for ads, embeds, and dynamic banners
Set explicit width/height on images and iframes; avoid injecting banners above existing text without reserving height.
Web fonts swapping line heights can cause CLS — preload only critical fonts.
Caching layers: object cache, page cache, CDN
Pick one coherent stack; stacking three page caches often breaks cart sessions or admin previews.
Purge caches after template changes, then re-test URL Inspection live render.
Prove the fix
Re-check the URL group in Search Console after a deployment cycle — CWV moves slowly because it is rolling user data.
If field data is still green but rankings lag, look to content and links — CWV is not the only lever.