A technical SEO checklist for modern JavaScript sites

Rendering, routing and metadata mistakes that quietly keep well-designed sites out of search results.

Search crawlers need a real URL for every meaningful page. Sections that only exist behind a hash fragment or a client-side tab share one URL, one title and one description — so only one of them can ever rank.

Give every route its own title, meta description and canonical URL, and make sure the canonical points at the page itself. A canonical that points at the homepage tells search engines to ignore everything unique about the page.

Check what the server actually returns. If the initial HTML is empty and content only appears after hydration, indexing becomes slower and less reliable. Server rendering or static generation removes that uncertainty.

Then measure Core Web Vitals on real devices rather than a fast laptop. Largest Contentful Paint is usually dominated by one hero image or web font, and both are fixable in an afternoon.