Technical SEO Every Developer Should Know Even If You're Not a Marketer

Most developers treat SEO as "someone else's job" — a marketing concern that happens after the site ships. But a huge chunk of SEO is actually decided at the code level, long before a marketer ever touches the content. If you're building sites — for clients, for yourself, or as side projects — a few technical fundamentals can make or break how discoverable that work ever becomes. Here's the technical SEO checklist I use when reviewing or building sites, from a digital marketing + web perspective. Core Web Vitals Aren't Optional Anymore Google uses three core metrics as direct ranking signals: LCP (Largest Contentful Paint) — how fast the main content loads INP (Interaction to Next Paint) — how responsive the page feels to input CLS (Cumulative Layout Shift) — how visually stable the page is while loading A site can have perfect content and still underperform in search if these numbers are bad. Common culprits: unoptimized images, render-blocking JS, and layout shifts from late-loading ads or fonts. Quick wins: Lazy-load offscreen images Serve modern image formats (WebP/AVIF) Reserve space for dynamic content (ads, embeds) to avoid layout shift Defer non-critical JavaScript Structured Data Is a Developer Task, Not a Marketing One Schema.org markup (JSON-LD is the recommended format) helps search engines — and increasingly AI-driven search summaries — understand what's actually on the page: is this a product, an article, a recipe, an FAQ? Sites with well-implemented structured data are more likely to get rich results (star ratings, FAQ dropdowns, breadcrumbs) in search — which directly impacts click-through rate even without a ranking change. If you're building a site and skip this step, you're leaving visibility on the table for something that's usually a few hours of implementation work. Rendering Strategy Affects Crawlability Client-side rendered (CSR) React/Vue apps can still get indexed, but it's inconsistent and slower than server-rendered or statically generate