Website migration SEO: the discipline of redirects

The new site goes live and everyone's happy: fresh design, fast pages, a tidy admin panel. Two weeks later someone opens the analytics dashboard and the mood changes — organic traffic has been cut in half. This is the most common and least discussed risk in any website migration: SEO is the furniture that falls off the truck.

The cause is almost never "Google didn't like the new site." It's far more mundane: the old URLs died, and nobody built bridges to the new ones. The good news is that this is an entirely preventable loss. Website migration SEO isn't magic — it's discipline.

Why do migrations lose rankings?

Google doesn't know you as a site; it knows you as a collection of URLs. Over the years, each of your pages has accumulated its own history: the links it earned, the rankings it won, the click data behind it. If /services/web-design ranks third, that ranking is attached to that address.

When the same content moves to /what-we-do/websites on the new site, Google has no way of knowing on its own. The old address starts returning 404; Google sees a page with years of accumulated value dying and a page with no history being born. The value doesn't vanish overnight, but the direction it drains in is not in doubt. The fix has a name: the 301 redirect — the signal that says "this page has permanently moved here." A 301 passes most of the old address's accumulated value to the new one. But only if someone actually sets it up.

Not every migration carries the same risk

"Migration" is not one thing; the risk scales with what changes. If only the design is being refreshed and URLs and content stay put, risk is low — though speed and internal links will still shift, so you measure anyway. If the URL structure changes, risk is medium-to-high, and the redirect map this post is really about becomes the core deliverable. If the domain changes, risk is highest: Google has to re-attach everything it knows about you to a new identity.

The riskiest scenario is doing all of it at once: new domain, new URL structure, new content, new design. When something goes wrong, you can't tell what went wrong, because four variables moved together. Stage the changes in layers if you can; if you can't, at least write down which layer changed what.

Before the move: no truck gets loaded without an inventory

The most critical work in migration SEO happens before a line of the new site is written: a complete URL inventory of the old one.

It comes from three sources. Search Console gives you the pages earning clicks and impressions — the ones actually doing work. Analytics gives you landing pages, which also catches non-organic traffic. And a crawler (Screaming Frog's free tier covers small sites) gives you every URL the site physically has.

This inventory reveals two things. First, where the value lives: you may have five hundred pages, but thirty of them probably carry most of the traffic. Second, the forgotten corners: old campaign pages, PDFs, a single blog post that picked up links years ago. The redirect plan needs a row for those too.

The redirect map: the real engineering of a migration

With the inventory done, every old URL gets its new counterpart written next to it. It's tedious spreadsheet work, which is exactly why it gets skipped. A few rules:

Map one to one. Every old page should point to the closest matching new page. Product page to product page, blog post to the same post's new address.

Don't redirect everything to the homepage. This is the most common shortcut: four hundred old URLs, all pointed at the front door. Google tends to treat this as a soft 404, and it's terrible for humans too — someone looking for a specific product lands on a generic brochure.

Keep chains short. If old address A points to B, and B points to C, flatten the chain: A goes straight to C. Sites that have migrated before accumulate these chains silently.

Be honest about deleted content. For pages with no equivalent on the new site, redirecting to the nearest category makes sense; for content with no remaining relevance, a proper 404 or 410 is better than a misleading redirect.

There's also the option of not changing URLs at all — and it's often the best one. If content stays at the same address, most of the redirect problem never exists. "New site" does not have to mean "new URLs."

Launch day: the checklist

Launch day is when mistakes are most expensive, because an unnoticed error runs for weeks. Check before you flip the switch, and again right after:

Has the noindex tag from staging been removed, along with any Disallow: / in robots.txt? This classic kills traffic even faster than missing redirects — it's an explicit instruction telling Google to forget you. Are the redirects actually returning 301, not 302 (which means "temporary")? Visiting your twenty or thirty most valuable old URLs by hand and watching them land on the right pages is half an hour well spent. Is the new sitemap live and submitted to Search Console? Are HTTPS, the www preference, and any hreflang tags consistent with the new structure?

Keep the old sitemap accessible for a while too — Google will crawl the old URLs from it and discover your redirects faster. And if the domain itself is changing, use Search Console's change-of-address tool; that's how you formally notify Google of the move.

After the move: what the first weeks tell you

A dose of realism: even the cleanest migration takes time for Google to digest, and a few weeks of fluctuation is normal. Most panic decisions — "roll it back!" — get made in this window, and they're usually wrong.

But fluctuation and bleeding are different things. The place to watch is Search Console: old URLs piling up in the 404 report are the signature of a forgotten redirect, and they can surface weeks after launch. Comparing rankings page by page is far more reliable than a general feeling about traffic. And when you find a lost page, it is never too late to add its redirect — a bridge built late still beats a bridge never built.

Whose job is this?

Migration SEO belongs to neither the developer alone nor the marketer alone; it lives at the intersection, and above all it depends on existing as a line item in the project plan. One question to ask whoever is building your new site cuts through everything: "Where in your proposal is the redirect map for our old URLs?" If the answer is a blank stare, think twice before loading your traffic onto their truck.

At Vucod, the redirect map is the non-negotiable part of every migration project — the new site doesn't launch until the old site's inventory is done. If you're planning a move like this, write to us at vucod.com; every inquiry gets an answer within 48 hours.