The verdict in three sentences
Changing CMS or domain name without a method loses 20 to 40% of organic traffic, sometimes for good. A controlled migration plan — URL mapping, 301 redirects, SEO QA, content freeze — budgets EUR 2,000 to 6,000 in 2026 and restores traffic in 4 to 12 weeks. The risk is never in the new design: it is in broken URLs and forgotten redirects.
The 6-step migration plan
An SEO migration is a project running parallel to the redesign, with its own deliverables. Here is the sequence that protects traffic.
| Step | Key action | Deliverable | Indicative cost (EUR) |
|---|---|---|---|
| 1. Mapping | Full crawl of old site + top pages | URL + traffic + backlinks table | 300 to 800 |
| 2. Redirect plan | 1:1 old → new URL mapping | Exhaustive 301 file | 500 to 1,500 |
| 3. Content freeze | No content edits during cutover | Content held iso | included |
| 4. Pre-prod QA | Test redirects, tags, sitemap | QA report | 400 to 1,200 |
| 5. Cutover + Search Console | Go live, new sitemap, indexing | Indexing request | 300 to 800 |
| 6. Post-migration monitoring | Rank tracking 4-12 weeks | Weekly report | 500 to 1,500 |
The most critical item is the 301 redirect plan: a single forgotten category can mean thousands of lost visits and dead backlinks.
The quantified risks of a botched migration
Putting a number on each mistake helps set the budget. Here are the typical 2026 losses.
| Common mistake | Estimated traffic loss | Recovery time | Fix cost |
|---|---|---|---|
| No 301 redirects | 30 to 40% | 8 to 16 weeks | Emergency, 2x the budget |
| Redirect chains (301→301→301) | 5 to 15% | 2 to 6 weeks | EUR 300 to 800 |
| URLs changed without mapping | 20 to 35% | 6 to 12 weeks | EUR 500 to 1,500 |
| Lost meta/H1 tags | 5 to 10% | 3 to 8 weeks | EUR 300 to 900 |
| Sitemap not updated | 3 to 8% | 2 to 4 weeks | EUR 150 to 400 |
| robots.txt block left in prod | 100% (deindexing) | 4 to 12 weeks | Critical emergency |
A blocking robots.txt left over from pre-prod is accident number one: it deindexes the entire site within days.
Mini case study
Karim runs a real-estate agency with 12,000 organic visits/month, 60% landing on listings and neighborhood pages. He moves from WordPress to a headless CMS. Without a plan he would lose ~4,000 visits/month. He invests EUR 4,500: mapping 380 URLs, full 301 mapping, pre-prod QA, 8-week monitoring. Result: a controlled 12% dip the cutover week, back to level by week 6, then +8% at week 10 thanks to the new site's performance gains. The avoided loss (4,000 visits at EUR 1.20 value/visit) far exceeds the project cost within the first month.
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FAQ
How long does an SEO migration take?
The SEO work spans 6 to 10 weeks: 2 to 3 before cutover (mapping, redirects, QA) and 4 to 12 after for monitoring and adjustments. The technical cutover itself takes a few hours.
Can you migrate with zero loss?
A temporary 5 to 15% dip in the first or second week is normal while Google recrawls. A well-run migration recovers everything, and often exceeds the starting level thanks to the new site's speed.
Should I keep the old URLs?
If possible, yes: preserving the URL structure avoids redirect risk. When change is unavoidable (new CMS, new domain), an exhaustive 301 mapping is non-negotiable.
Is changing the domain name risky?
More so than a plain CMS change, since all authority must transfer. With clean 301s and Search Console's change-of-address tool, recovery usually takes 4 to 8 weeks.
When in the year should I migrate?
Avoid your seasonal peaks. A real-estate agency should migrate in low season; an e-commerce site never before the holidays. A stable-traffic window lets you measure impact cleanly.
Let's scope your project. Tell us your current CMS, URL volume, and target date, and we'll price a secured SEO migration plan (EUR 2,000 to 6,000) with guaranteed post-cutover 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.
