How can I migrate 2,000–3,000 static HTML pages to a CMS without losing SEO?

You may not need a traditional CMS at all if the site is mostly static content. A static-site generator or a lightweight CMS could provide a modern responsive design while retaining much of the existing architecture. That can avoid unnecessary URL changes and reduce maintenance overhead. If you do choose WordPress, import the content as pages or posts and configure its permalink structure to match the old paths as closely as possible.

Do it in batches instead of moving all 2,000–3,000 pages at once. Start with a group of lower-risk or lower-traffic pages, compare their performance with the old versions, and fix any issues before expanding the migration. Put the new setup on staging first, but make sure it cannot be indexed there. Test redirects, canonicals, XML sitemaps, robots.txt, internal links, mobile rendering, and page speed before changing DNS.

Plan for some volatility after the migration, but you can reduce the risk considerably. Crawl and archive the current site first, including every URL, title, meta description, heading, canonical tag, status code, and internal link. Preserve the existing URL structure wherever possible. For URLs that must change, create a carefully tested one-to-one 301 redirect map rather than sending everything to the homepage. Keep the important content and on-page signals intact, then monitor rankings, traffic, crawl errors, and indexing after launch.

Before deciding what to migrate, audit the content itself. Identify pages that attract traffic, earn links, or support important topics, and review stale or duplicate pages rather than automatically carrying everything over. A CMS switch alone will not solve declining traffic, and changing the domain, URLs, software, and content at the same time creates much more risk. Preserve valuable pages and improve them in a controlled sequence.