301 redirects without breaking SEO: how we build the redirect map

Migrator's diary. If there's one moment where a migration can go down the drain, it's this one: the redirects. It's the boring, invisible, critical part. Doing it right goes unnoticed (everything stays the same in Google); doing it wrong gets noticed a lot (traffic drops and it takes months to recover). This is how we do it, no shortcuts.

What a 301 is and why it matters so much

A 301 redirect tells Google: "this address has moved here, permanently". And —this is the important part— it passes almost all the authority the old URL had built up over the years on to the new one. Without a 301, every URL that changes starts from zero in Google. With a well-made 301, you keep your rankings even if the structure changes.

The process, in four steps

1. Full URL inventory. Every address Google knows about: from the current sitemap, from Search Console and from crawling the site. Whatever isn't on the list gets lost.
2. 1:1 map. Every old URL pointed at its new URL. Ideally most of them don't change (same address → zero redirects needed).
3. Redirects for what does change. Only where the address really changes, one clean 301. No redirect chains (A→B→C): always direct, A→C.
4. Validation. Each old URL is checked one by one to confirm it leads to the right new one, with a 301 code, before touching the DNS.

The most common mistake: changing what doesn't need changing

When we migrate from WordPress, our number one priority is keeping the URLs exactly as they are. If your post lived at /blog/my-article, on the new site it still lives at /blog/my-article. Zero redirects, zero risk. Only when the old structure is a mess —URLs with ?p=123, duplicate categories, plugin parameters— do we take the chance to clean up, and that's where the 301s come in.

Be wary of anyone selling you "migration with redirects" as if redirecting a lot were a good thing. The best migration is the one that needs the fewest redirects possible, because it keeps your URLs. Redirecting is plan B for what can't stay the same, not a trophy.

After the switch: monitor, don't pray

The work doesn't end on switch day. Over the following weeks we watch Search Console for coverage (that Google is crawling properly), 404 errors (URLs that slipped past us) and rankings. If a 404 shows up, it gets fixed with its 301 on the spot. It's the difference between "we hope it goes well" and "we know it's going well".

SEO preservation isn't an extra: it's the foundation of how we migrate. Full context in the migration guide, and if you want us to audit your current URLs, the audit is free.