The verdict in three sentences
A botched site migration cuts organic traffic by 20 to 40 %, but a well-run one keeps the loss below 5 %. The key is a URL-by-URL 301 redirect plan, preserved tags and a before/after crawl so nothing slips through. Count on 3,000 to 9,000 EUR depending on URL volume, with a risk window of 4 to 8 weeks.
Migration budget by URL volume
Cost is driven mainly by the number of URLs to map and the mapping complexity (merges, splits, structure changes). Here are the 2026 ranges.
| URL volume | 2026 budget | Duration | Mapping complexity |
|---|---|---|---|
| < 500 URLs | 3,000 - 4,500 EUR | 2-3 weeks | Simple, 1:1 |
| 500 - 1,500 URLs | 4,500 - 6,500 EUR | 3-5 weeks | Medium, some merges |
| 1,500 - 5,000 URLs | 6,500 - 9,000 EUR | 5-8 weeks | High, tree rework |
| > 5,000 URLs | On quote | 8-12 weeks | Very high, e-commerce |
Preserving title, meta, Hn, canonical tags and structured data is included in a serious budget: never cut this line, it's the number-one cause of drops.
Migration checklist and causes of decline
SEO success rides on a rigorous checklist. Here are the critical steps and the most common causes of loss in 2026.
| Step | Action | Cause of drop if neglected |
|---|---|---|
| Pre-crawl | Full URL inventory | Forgotten, orphan URLs |
| 301 mapping | Old URL to new one | Missing redirects = 404 |
| Tag preservation | Title, meta, Hn, canonical | Loss of semantic relevance |
| Structured data | JSON-LD carried over | Loss of rich results |
| Robots + sitemap | Update, resubmit | Deindexation, crawl budget |
| Post-crawl | Verify 200/301/404 | Redirect chains, loops |
| Technical QA | Speed, mobile, HTTPS | CWV drop = ranking drop |
A redirect chain (301 to 301 to 200) dilutes PageRank and slows the page: each redirect must point directly to the final URL. Typical recovery time is 4 to 8 weeks after correction.
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Mini case study
Thomas is digital lead at a B2B services SME migrating from WordPress to a headless CMS, with 1,800 URLs. He budgets 6,000 EUR for the migration, of which 1,200 EUR for 301 mapping and QA alone. Without a plan, a comparable migration had lost a competitor 28 % of traffic. Thanks to the before/after crawl and URL-by-URL mapping, his loss is limited to 4 % in week one, fully recovered by week 6. On 55,000 organic visits/month valued at 1.10 EUR/visit, he avoids a ~16,000 EUR traffic-value loss over the quarter.
FAQ
How long is the risk window? Count 4 to 8 weeks after go-live, the time for Google to recrawl and reindex. Monitor Search Console daily during this period.
Should I keep old URLs? No, but every old URL must 301-redirect to its most relevant equivalent. A blanket redirect to the homepage is treated as a soft 404 and loses SEO equity.
When does recovery show? First recoveries appear in 2 to 3 weeks; full stabilization takes 4 to 8 weeks for an average site, longer for a large e-commerce.
Can I migrate with zero loss? A transient 2 to 5 % loss is normal during recrawl. The realistic goal is < 5 %, back to baseline within 8 weeks.
What's the worst time to migrate? Avoid activity peaks (sales, campaigns) and Fridays. Migrate early in the week, off-peak, with the team on hand to react.
Let's scope your project. Tell us your current platform, the target and your URL volume: we'll price the redirect plan, QA and a safe go-live window. 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.
