Most traffic collapses after a relaunch are not caused by the new site being worse. They are caused by the old URLs no longer resolving. Every ranking you hold is attached to a specific address, and if that address returns a 404, the ranking has nowhere to go.
Start with a full inventory
Before anything is designed, export every URL that exists today: from your sitemap, from Search Console, from analytics, and from a crawl of the live site. You are looking for the union of all four, because each misses something the others catch.
Sort by traffic and by inbound links. Those pages are the ones whose addresses matter most.
Map old to new, one by one
Every old URL needs a destination. The rule is that a redirect should land on the closest equivalent page, not the homepage. A blanket redirect of everything to the homepage is treated as a soft 404 and passes almost nothing.
Use permanent redirects. Next.js emits 308 for permanent redirects rather than 301, which Google treats as equivalent, so that is not a defect to chase.
Keep what already ranks
If a page ranks well and you cannot improve it, keep its URL exactly as it is. Renaming a URL to be tidier is a real cost with no upside. Redesign the page, keep the address.
Do not let staging get indexed
A staging site that Google crawls creates a duplicate of your entire website. Protect it with authentication, not just a robots directive, because a robots rule does not prevent indexing of a URL that is linked elsewhere.
Launch day
- Verify redirects with a crawler before DNS changes, using the new host directly.
- Confirm the sitemap is regenerated and submitted. A sitemap baked at build time will not reflect content added after that build.
- Check that analytics and conversion tracking still fire on the new templates.
- Watch server logs for 404 spikes; that is your fastest signal of a missed mapping.
The first thirty days
Expect movement. Rankings usually dip for one to three weeks while the new pages are recrawled and reassessed, then recover. What is not normal is a dip that keeps deepening after a month; that indicates a structural problem, most often missing redirects or blocked resources.
Keep the old site's redirect map in place indefinitely. There is no expiry date on an inbound link from 2019.
Frequently asked questions
Should I migrate content and design at once?
If you can avoid it, no. Changing URLs, content and design simultaneously makes it impossible to tell which change caused a drop.
How long do I keep redirects?
Permanently. They cost nothing to serve and continue passing value for years.
