Q: After replatforming, rankings slipped even with redirects — was it the new templates?

Q: After replatforming, rankings slipped even with redirects — was it the new templates?

This is the migration problem nobody warns you about.

Short answer: very likely yes — the HTML changed, not just the URLs.

Long answer: a site moved CMS, kept URLs and 301s clean, but rankings still slid 15%. The culprit: the new platform's templates dropped the H1 on category pages, shortened title tags, and lazy-loaded body text in a way Google rendered as thin. Content looked the same to humans, weaker to crawlers.

We restored proper H1s, full titles, and server-rendered the main copy. Rankings recovered over 6 weeks and the worst pages came back fastest.

Next step: don't only diff URLs — diff the rendered HTML of old vs new pages (titles, H1, word count, schema). Redirects preserve the address; they don't preserve the content.