Why Technical SEO Actually Matters Now
For years, technical SEO was treated as a nice-to-have. Get your keywords right, get some backlinks, and you'd rank. That calculus has shifted.
Core Web Vitals — Google's user experience metrics — are now confirmed ranking signals. A site that loads slowly, shifts layout unexpectedly, or responds sluggishly to interaction will rank below a competitor with comparable content but better performance.
For startups, this is both a challenge and an opportunity. Most startup websites are not technically optimised. Getting ahead of this is a genuine competitive advantage.
The Three Metrics That Matter
Largest Contentful Paint (LCP) measures how long the main content of a page takes to load. Good: under 2.5 seconds. Needs improvement: 2.5–4.0 seconds. Poor: above 4.0 seconds.
Cumulative Layout Shift (CLS) measures visual stability — how much elements move around while the page loads. Good: under 0.1. Anything above 0.25 is a significant user experience problem.
Interaction to Next Paint (INP) replaced FID in March 2024. It measures responsiveness — how quickly your page responds to user interactions. Good: under 200ms. Poor: above 500ms.
Diagnosing Your Current State
Start with Google Search Console's Core Web Vitals report. This shows your real-user data (field data) segmented by page. It's more reliable than lab data because it reflects actual user conditions.
Supplement with:
- PageSpeed Insights: Lab data + field data, with specific recommendations
- Chrome DevTools Performance tab: Deep-dive diagnostics for LCP and INP
- Lighthouse: Comprehensive audit in CI/CD pipelines
For CLS specifically, the Layout Instability API lets you log shifts in production and attribute them to specific elements.
Fixing LCP
The most common LCP culprits:
Slow server response: Add a CDN. For Next.js sites on Vercel, this is automatic. For others, Cloudflare's free tier provides global edge caching.
Render-blocking resources: CSS and JavaScript that block rendering delay LCP. Audit your <head> for non-critical stylesheets loaded synchronously. Move them to deferred loading.
Unoptimised images: The LCP element is almost always an image. Use next/image (or equivalent) for automatic WebP conversion, responsive sizing, and lazy loading. Set the priority attribute on your hero image so it's not lazy-loaded.
No preloading: If you know what the LCP element will be, add a link preload tag to fetch it before the browser discovers it in the HTML.
Fixing CLS
CLS is caused by layout shifts — elements that move after the page appears to have loaded.
Always size images: Include explicit width and height attributes on every img element. Without them, the browser doesn't know how much space to reserve.
Reserve space for dynamic content: Ads, embeds, and async-loaded content (like chat widgets) should have a fixed-size container so their arrival doesn't push content down.
Avoid inserting content above existing content: The most damaging shifts are at the top of the page. Cookie banners, notification bars, and sticky headers that appear after load are frequent offenders.
Fixing INP
INP is the newest and often most misunderstood metric. It measures interaction responsiveness across the entire page visit, not just the first interaction.
Common causes:
- Long JavaScript tasks blocking the main thread during interactions
- Heavy event handlers (search, filtering, form validation) doing synchronous work
- React re-renders touching too many components on user input
Solutions:
- Break up long tasks with scheduler.yield() or setTimeout(fn, 0)
- Move expensive work to Web Workers
- Debounce expensive event handlers (search, resize)
- Use React's startTransition for non-urgent state updates
The On-Page SEO Layer
Core Web Vitals are one part of technical SEO. Don't neglect:
- Proper heading hierarchy (one H1 per page)
- Descriptive title tags (under 60 characters)
- Meta descriptions (under 160 characters)
- Canonical tags to avoid duplicate content
- Schema markup for your content type (Article, FAQPage, Product, LocalBusiness)
- XML sitemap submitted to Google Search Console
A site with excellent Core Web Vitals and solid on-page SEO will outperform a fast site with poor fundamentals — and certainly outperform a slow site with great keywords.
Want an SEO audit for your site? Get in touch →