Redirect Mistakes That Kill SEO After a Migration

The most expensive mistake is shipping a redirect map that was never tested against real URLs, including trailing slashes, upper case, and legacy query parameters. Search engines may see soft 404s or redirect loops while the team believes the map is "done."

Using 302s for permanent moves, or mixing redirect plugins with server rules, creates inconsistent signals. You want one canonical source of truth for HTTP rules, and 301 (or 308) for permanent URL changes. Long chains and hop limits waste crawl budget and dilute signals.

Forgetting faceted, filtered, and paginated URLs is common. If old parameter URLs 404 or redirect incorrectly, you can lose long-tail traffic without noticing until Search Console shows steep drops. Test parameter handling explicitly.

After launch, monitor coverage, redirect errors, and server log samples for 404 spikes. Do not treat SEO migration as a launch-day task only; the first two to four weeks often need surgical fixes as edge URLs surface.

If rankings fall, start with indexation and redirect integrity before assuming "content quality." Many recoveries are technical, not editorial.