Screaming Frog vs a redirect-mapping script for a 12k-URL migration

Screaming Frog vs a redirect-mapping script for a 12k-URL migration
A publisher moved CMS. I tested both approaches on the real cutover.

Screaming Frog (list mode + redirect audit)
➕ Crawled all 12k old URLs post-launch, flagged 340 redirect chains and 28 loops in one pass
➕ The redirect chain report showed exact hop counts to flatten
➖ Mapping old→new still needed a manual VLOOKUP beforehand

DIY script
➕ Free, fast to generate the map
➖ No verification — it can't tell you a rule fired wrong in production

The case: Frog caught 340 chains that would've leaked equity through 3-hop redirects. We flattened all to single 301s pre-deindex. Result: organic traffic dipped only 4% post-migration and fully recovered in 18 days — vs the 20-30% drop the client feared.

Best for: Frog for post-launch verification; nothing else does it as fast.
Price-vs-value: £199/yr to de-risk a migration is trivial.

Pick Frog for any migration over 500 URLs.
Skip it only for tiny static sites.