SEO for Developers: Practical Checklist for Next.js

SEO has two modes: “this is fine” and “why is Google indexing my 404 page with my login screen title.” This is a practical checklist for Next.js apps using the App Router.

1) Get the basics right (Metadata)

• Set a unique title + description per page.
• Add canonical URLs to avoid duplicate pages competing with themselves.
• Use Open Graph + Twitter metadata so links look good when shared.

In Next.js App Router, prefer export const metadata for static pages, and generateMetadata() when it depends on route params.

2) Make pages crawlable (no accidental “invisible site”)

• Ensure robots.txt doesn't block your whole site (it happens more than you'd think).
• Don't hide important content behind client-only rendering if you can avoid it.
• Avoid requiring auth/cookies for public pages (bots don't RSVP).

3) Ship a sitemap (and keep it correct)

A sitemap is a polite list of URLs you want indexed. It won't magically rank you, but it makes discovery and recrawling easier—especially for new sites.

• Include only canonical, indexable pages.
• Exclude staging/preview domains.
• Update it when routes change (you will forget once).

4) Use structured data where it matters

If you have articles, add JSON-LD (Article schema). If you have projects/products, consider the relevant schema types. Structured data helps search engines understand your content; it doesn't guarantee fancy rich results, but it's the closest thing SEO has to documentation.

• Validate it using Google's Rich Results test.
• Don't lie in schema (you'll just get ignored or penalized).

5) Performance is SEO (because users bounce, and Google notices)

• Optimize images with next/image and sane sizes.
• Avoid shipping a nightclub of JS to render three paragraphs of text.
• Watch LCP/CLS/INP in the field, not just Lighthouse on your laptop.

6) Content hygiene (the boring part that wins)

• Write headings like you mean them (H1 once, H2/H3 for structure).
• Make URLs stable and human-readable.
• Keep your internal links intentional (help crawlers, help users).

7) A quick Next.js checklist

• Per-route metadata via metadata/generateMetadata
• Canonical URLs
• Open Graph + Twitter cards
• Sitemap
• Robots
• Accessible, semantic HTML
• Fast pages, minimal client JS

The trade-off: doing SEO "properly" means being disciplined about content structure and performance. It's not glamorous—like tests—but it saves you from explaining to your manager why your homepage ranks for “untitled document.”