Core Web Vitals in 2026
The three Core Web Vitals are LCP (Largest Contentful Paint, ≤2.5s), INP (Interaction to Next Paint, ≤200ms), and CLS (Cumulative Layout Shift, ≤0.1). INP replaced FID in March 202…
Read article →INP Replaces FID — What Changed
FID measured the delay before the browser could start handling the first input. INP measures the round-trip latency of every interaction, then reports the worst…
Read article →CLS Root Causes
The four classic CLS sources: images without explicit dimensions, ads and embeds, dynamically injected content above existing content, and fonts loading after the initial render.Fi…
Read article →AVIF vs WebP for Real Sites
AVIF typically delivers 30–50% smaller files than WebP at the same perceived quality, but encodes much more slowly.The right pattern: serve AVIF if the browser…
Read article →Font Subsetting Saves Real Bytes
A typical web font ships every Latin glyph plus extensive language coverage you do not use. Subsetting to just the characters you render trims it…
Read article →font-display: swap vs optional
font-display: swap shows fallback text immediately, swaps to the web font when ready. The cost is a visible swap on slow connections.font-display: optional gives the…
Read article →Critical CSS in the Modern Era
Inline the CSS needed to render above-the-fold content; load the rest asynchronously. The savings on slow networks are real — first paint happens on the…
Read article →HTTP/3 in Practice
HTTP/3 runs over QUIC, which uses UDP. The big win is head-of-line blocking elimination at the transport layer — one slow packet does not stall…
Read article →Brotli vs gzip: When Brotli Wins
Brotli compresses 15–25% better than gzip for HTML, CSS, and JS at higher compression levels. The catch is encoding cost — Brotli level 11 is…
Read article →Schema.org JSON-LD: What to Emit
Five high-value types: WebSite with SearchAction, Organization or Person for brand identity, BreadcrumbList on every inner page, Article/BlogPosting on posts, and Product on commer…
Read article →