A JavaScript site can pass every classic SEO check and still be effectively invisible, because the crawler saw an empty shell. Test rendering first.
Rendering
- 1.Fetch the page with JavaScript disabled and read the HTML that arrives — the main content and internal links should be present
- 2.Use the URL Inspection tool in Search Console and read the rendered HTML, not the screenshot
- 3.Confirm the title, canonical and meta description exist in the server response rather than being injected on the client
- 4.Check that route changes update the title and canonical, which client-side routers frequently fail to do
Indexation
- One self-referencing canonical per page — frameworks often emit two when a layout and a page both declare one
- No accidental sitewide noindex left over from a staging environment
- A sitemap listing only canonical, indexable, 200-status URLs
- robots.txt that does not block the JavaScript and CSS bundles needed to render the page
Links must be links
A div with a click handler is not a link. Crawlers follow anchor elements with href attributes. If your framework offers a link component, use it and let it emit a real href — this single issue orphans more pages than any other on modern sites.
Core Web Vitals in the field
Lab scores are a debugging tool, not a verdict. Use the Core Web Vitals report in Search Console and field data from real users. On JavaScript sites the usual offenders are oversized hydration bundles hurting Interaction to Next Paint, and hero images without dimensions causing layout shift.
Structured data
Emit JSON-LD server-side. Match the schema type to the page: Organization or WebSite sitewide, Article on posts, Product on product pages, FAQPage where a genuine question and answer block exists. Validate with the Rich Results Test after every template change.
Migration safety
Before any replatform: crawl and archive the current URL set, map every URL to its new destination, keep content parity on the pages that earn traffic, and monitor Search Console daily for the first month. Most ranking losses attributed to redesigns are redirect failures.