The verdict in three sentences
A botched migration can drop traffic by 30 to 50 % for months: a well-scoped one keeps the loss to under 10 %, recovered in 6 to 10 weeks. The key is an exhaustive 301 redirect plan covering 100 % of indexed URLs, backed by a before/after comparative crawl. Plan an SEO support budget of 1,500 to 4,000 EUR and a 4 to 8 week vigilance window.
The costed pre- and post-launch checklist
A migration is decided as much before as after the switch. Here are the essential steps and their criticality.
| Step | Timing | Criticality | Deliverable |
|---|---|---|---|
| Full crawl of current site | D-30 | Critical | 100 % URL inventory |
| URL mapping old -> new | D-21 | Critical | Correspondence table |
| Content freeze | D-7 | High | No last-minute changes |
| 301 redirects in place | D-day | Critical | 100 % redirect testing |
| Submit new sitemap to GSC | D+1 | High | Accelerated reindexing |
| Comparative crawl post-switch | D+3 | Critical | Detect 404s/chains |
| Monitor rankings/errors | D+1 to D+56 | High | Weekly GSC tracking |
The content freeze avoids last-minute fixes that break the mapping. The comparative crawl is your safety net: it immediately spots orphaned URLs and redirect chains to fix.
Budget and tolerance thresholds
How much does support cost, and which thresholds should you accept without panic?
| Item | Budget (EUR) | What it covers |
|---|---|---|
| Pre-migration audit | 500 - 1,200 | Crawl + mapping |
| 301 redirect plan | 400 - 1,000 | Mapping + tests |
| Post-launch support (8 wk) | 600 - 1,800 | GSC monitoring + fixes |
| Total support | 1,500 - 4,000 | Safe migration |
Tolerance thresholds to keep in mind: a temporary 5 to 10 % traffic dip in the first week is normal while Google reindexes. Beyond 15 %, or if the drop persists after 4 weeks, audit the redirects urgently.
Mini case study
Marie, digital manager of a services SME in Berlin, rebuilds a 240-page indexed site generating 12,000 visits/month. She invests 2,800 EUR in support: crawl, mapping of the 240 URLs, 301 redirects tested at 100 %, GSC monitoring over 8 weeks. Maximum drop observed: 8 % in week 2, back to baseline by week 7. With 45 monthly leads at stake, she avoids an estimated 15-20 lead loss that an unscoped migration would have cost.
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FAQ
Do I really need to redirect 100 % of URLs?
Yes, every indexed URL or one with backlinks. A forgotten URL returns a 404, loses its SEO equity and frustrates visitors arriving from an external link.
How long does the traffic dip last?
With a clean plan, 4 to 8 weeks of fluctuation then a return to baseline around week 6 to 10. Without a plan, the drop can last several months.
Is the sitemap enough to prevent loss?
No: the sitemap speeds reindexing but does not replace 301 redirects. Both are complementary and indispensable.
When should I worry after the switch?
If the drop exceeds 15 % or persists beyond 4 weeks. A comparative crawl then reveals 404s, redirect chains or badly transferred canonical tags.
Can I migrate and redesign at the same time?
Yes, it is common during a rebuild. You just need to isolate the variables: URL structure, content and technical must be tracked to diagnose any drop.
Let's scope your project. Tell us your number of indexed pages and target launch date, and we will cost a migration support package with a guaranteed redirect plan. 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.
