· 1 min read
Core Web Vitals: the fixes that pay off first
Where to look first when a website feels slow — images, fonts, scripts and layout shift.
- Website performance
- React
- Development lessons
Performance work can feel endless, but a handful of causes explain most slow websites. Fix these first and you will usually see the biggest change.
Images
Oversized images are the most common culprit. Serve modern formats, size them to how they are actually displayed and load off-screen images lazily. The largest image above the fold should load with priority, since it often defines the Largest Contentful Paint.
Fonts
Custom fonts can block text from appearing. Self-host them, limit the number of families and weights, and make sure text stays visible while the font loads.
JavaScript
Every kilobyte of JavaScript has to be downloaded, parsed and executed. Audit what ships to the browser, remove unused dependencies, and load heavy or rarely used features on demand instead of up front.
Layout shift
Content that jumps as the page loads is frustrating and hurts your Cumulative Layout Shift score. Reserve space for images, embeds and late-loading elements so the layout stays still.
Third-party scripts
Analytics, chat widgets and tag managers add up. Load only what you need, and defer everything that is not essential for the first view.
Measure, then change
Use real measurements — Lighthouse for a quick check, field data for the truth — and change one thing at a time. Improvements you can measure are improvements you can keep.