PageSpeed & Performance

Server-side compression methods that shrink text resources like HTML, CSS and JavaScript before transmission — Brotli usually delivers better ratios than Gzip today.

A distributed server network that delivers static — and increasingly dynamic — content from the geographically nearest edge server to the user.

The critical rendering path is the sequence the browser runs to turn HTML/CSS/JS into pixels parsing, render tree, layout, paint. Optimizing it shortens first paint and LCP.

CrUX is Google's public field-data dataset of real performance values from Chrome users (opt-in). It's the source of Core Web Vitals scoring in Search Console and PageSpeed Insights — not synthetic.

FCP measures when the browser renders the first visible DOM element (text, image, SVG). "Good" at ≤ 1.8 s. The earliest signal that the page is responding — not a Core Web Vital, but an important PageSpeed metric.

Field data are real performance values from actual users (CrUX, RUM). Lab data are synthetic measurements under controlled conditions (Lighthouse, WebPageTest). Google ranks by field data — lab data only hints at trends.

Modern versions of the HTTP protocol that deliver parallel requests over a single connection (HTTP/2) or via the faster QUIC transport (HTTP/3).

Using modern image formats (WebP, AVIF) plus appropriate sizes and compression to dramatically shrink image payloads without visible quality loss.

Lazy loading is a technique where images, iframes, or JavaScript modules load only when actually needed — usually when scrolled into the viewport.

Lighthouse is Google's open-source audit tool that synthetically measures a page's performance, accessibility, best practices, and SEO in a controlled environment.

PageSpeed Insights is Google's free web tool that combines Lighthouse lab scores with CrUX field data from real Chrome users and outputs concrete optimization suggestions.

Resource hints in the HTML head that tell the browser to fetch resources earlier, set up connections in advance, or accelerate DNS lookups.

Render-blocking resources are CSS and JavaScript files the browser must load and parse before it can render. They delay FCP and LCP — minimize them with async/defer, inline critical CSS, and remove unused CSS.

TTFB measures the time from request start to the first byte received. It sums DNS, TCP, TLS, and server processing. Rule of thumb — good < 200 ms, problematic > 600 ms; directly affects LCP and FCP.