One-to-one redirect map vs regex pattern rules — migration tool choice

One-to-one redirect map vs regex pattern rules — migration tool choice
Replatformed a 12k-page site. Dev wanted a single regex to map old to new. It mangled 400 edge cases.
— Regex/pattern rules: one rule covers thousands of URLs when the structure maps cleanly (/old-cat/X to /new-cat/X). Fast, light on the server.
— One-to-one map: explicit row per URL, zero surprises, but a nightmare to maintain at scale.
The move: regex for the clean 90% where the pattern truly holds, then a one-to-one map layered on top for the messy 10% — renamed categories, merged pages, killed SKUs.
Always test regex redirects against your full old-URL export before launch. One greedy pattern can silently 301 your homepage into a product page. Crawl the old list, confirm every target 200s.