The fastest website is the website that is already loaded, and that’s exactly what HTTP caching delivers. HTTP caching is a powerful technique that lets web browsers reuse previously loaded resources like pages, images, JavaScript, and CSS without downloading them again. Understanding HTTP caching headers is essential for web performance optimization, but misconfiguration can cause big performance problems.

GTMetrix used to be the go-to tool for checking website speed, but let’s be honest—paying for one-off synthetic tests isn’t worth it. If you’re still relying on synthetic testing alone, you’re missing a big part of the web performance picture. If you care about Core Web Vitals, SEO performance, and user experience, you need more than just lab data. The good news? There are better (and free) alternatives like PageSpeed Insights and WebPageTest for synthetic testing.

HTTP/3 is here, and it’s a big deal for web performance. See just how much faster it makes websites! Wait, wait, wait, what happened to HTTP/2? Wasn’t that all the rage only a few short years ago? It sure was, but there were some problems. To address them, there’s a new version of the venerable protocol working its way through the standards track. Ok, but does HTTP/3 actually make things faster? It sure does, and we’ve got the benchmarks to prove it.

Images are big. Really big. The bytes required for an image dwarf most site’s CSS and JavaScript assets. Slow images will damage your Core Web Vitals, impacting your SEO and costing you traffic. Images are usually the element driving Largest Contentful Paint and load delays can increase your Cumulative Layout Shift. If you’re not familiar with these metrics, check them out in the Definitive Guide to Measuring Web Performance.