What is render-blocking (and why it slows your site)?

Render-blocking resources are files — usually CSS and JavaScript — that the browser must load before it can display your page. Too many, or badly-handled ones, delay how quickly visitors see anything.

Why it matters

• •It slows down First Contentful Paint — the first thing people see.
• •A slow first paint feels sluggish and loses visitors.
• •It's a common Core Web Vitals issue.

How it's reduced

Techniques like deferring non-critical JavaScript, streamlining CSS, and loading fonts efficiently cut render-blocking. These are handled by a well-built site's tooling, but they're a big reason some sites feel instant and others crawl.