What a Visitor Waits For

Performance is how long a person waits and what they see while waiting. Measure before changing anything: the bytes a page downloads, the moment readable content appears, and how often the browser has to recalculate the page. On this site, shipping stylesheets without their commentary cut the compressed core download by 40% without changing a rule, and the full week-by-week history can be rebuilt from git.

#>performance_essentials

Performance Essentials

What people feel

Web Vitals name loading, responsiveness, and visual stability as measurable targets.

web.dev: vitals

The field guide

MDN's overview of how pages load, render, and respond.

mdn: performance

Watch it happen

Record a trace and read where the time goes.

devtools: performance

Skip what is off screen

Let the browser defer layout for content no one can see yet.

mdn: content-visibility