XML Sitemaps: Best Practices for Large Websites
XML Sitemaps are machine-readable lists of all indexable URLs. In Next.js 15, the sitemap.ts file convention replaces third-party plugins and enables dynamic generation from CMS data.
Key Takeaways
- ✓Maximum 50,000 URLs or 50MB per sitemap file
- ✓Only update lastmod when content actually changes
- ✓Only include indexable URLs (no noindex, no 404)
- ✓Sitemap index for more than 50,000 URLs
- ✓In Next.js: sitemap.ts file convention with ISR revalidation
- ✓Hreflang in sitemaps for international sites
XML Sitemaps are a cornerstone of technical SEO — especially for large websites with dynamic content.
Limits and Format
Maximum 50,000 URLs or 50MB per sitemap file. For larger sites: sitemap index with references to individual sitemaps. Set lastmod only when content actually changes — automatic daily updates without changes dilute the signal.
Next.js Implementation
The sitemap.ts file convention in Next.js App Router replaces third-party plugins and enables dynamic generation from Payload CMS data with ISR revalidation.
“A sitemap is like a roadmap for search engines. It helps them discover pages that might not be found through normal crawling.”
— Gary Illyes, Google Search Analyst