The verdict in three sentences
A poorly prepared site migration is the fastest way to destroy years of SEO in one night. In 2026, a 301 redirect plan costs 800-3,000 € depending on URL count and keeps traffic loss under 5 %, versus -30 to -50 % without a plan. It is insurance, not an option.
What a redirect plan covers in 2026
The core issue: every old URL that ranked must point, via a 301, to its most relevant equivalent on the new site. That requires exhaustive mapping, 404 handling, a before/after control crawl, and 4 to 8 weeks of post-migration monitoring.
| Service | 2026 range (€ excl. VAT) | Depends on | Deliverable |
|---|---|---|---|
| URL mapping (small site < 100 URLs) | 800 - 1,300 | Volume | Complete 1:1 table |
| URL mapping (100-1,000 URLs) | 1,400 - 2,400 | Volume | Mapping + prioritization |
| URL mapping (> 1,000 URLs) | 2,500 - 3,000+ | Volume | Semi-automated mapping |
| Before/after control crawl | 400 - 800 | Complexity | Gap report |
| Post-migration monitoring 4-8 wks | 500 - 1,200 | Duration | Rankings reporting |
The quantified risks of a botched migration
Without a plan, errors stack up: orphan URLs, redirect chains, mass 404s, unpublished content. Each carries a measurable SEO cost.
| Common error | Organic traffic impact | Fix |
|---|---|---|
| No 301 redirects | -30 to -50 % | Full mapping plan |
| Redirect chains (>2 hops) | -5 to -10 % | Direct 1:1 redirects |
| 404s on ranking pages | -10 to -25 % | Redirect or recreate |
| Lost meta tags | -5 to -15 % | Migrate metadata |
| Sitemap not updated | Slower recrawl | Submit new sitemap |
Mini case study
Sophie, acquisition lead at a software vendor, rebuilds her 600-URL site, 180 of which drive organic traffic. Without a plan, a -40 % scenario would drop her 5,000 visits/month to 3,000, i.e. 2,000 lost visits and ~8 monthly leads gone. She invests 2,100 € in a redirect plan plus 900 € monitoring. Result: loss capped at -4 % in month one, back to baseline in 6 weeks. 3,000 € spent protects the equivalent of 8 leads/month, i.e. tens of thousands of euros in pipeline.
FAQ
Need a professional website?
Kolonell builds websites that attract clients, optimized for the Sénégalese market. Free quote in 2 minutes.
301 or 302 for a redesign?
Always 301 (permanent). A 302 is temporary and does not fully pass SEO authority. Using a 302 by mistake on a permanent migration dilutes your rankings.
How long before traffic recovers?
With a good plan, 2 to 6 weeks to regain the baseline as recrawl completes. Without a plan, recovery can take 6 months or never fully happen.
Should I keep old URLs when possible?
Yes, when realistic. Preserving the URL structure avoids thousands of redirects and removes the associated risk. A design redesign does not require changing URLs.
What about pages with no equivalent on the new site?
Redirect to the closest parent page (category, service), not the homepage. An irrelevant redirect is barely better than a 404 in Google's eyes.
Can I migrate without an SEO agency?
On a small site, yes, with method. Beyond 100 ranking URLs, the financial risk far exceeds the cost of a professional plan. It is one of the few areas where saving costs you dearly.
Let's scope your project. Share your URL count and switch-over date, and we'll deliver a redirect plan and post-migration monitoring. Detailed quote within 48 h. WhatsApp +221 77 596 93 33.
Mohamed Bah
Fondateur, Kolonell
Passionate about digital and entrepreneurship in Africa, Mohamed has been helping Sénégalese businesses with their digital transformation since 2020. Founder of Kolonell, he believes every SME deserves a professional and accessible online présence.
