The verdict in three sentences
Migrating a multilingual site is not migrating one site three times: it is managing hreflang and per-language 301 redirects that must stay mutually consistent. Budget 14,000-28,000 GBP for the full migration and 1,800-3,500 GBP for the international SEO audit, over 8 to 14 weeks. The main risk: cross-language cannibalization or per-market loss if hreflang is misconfigured.
The budget step by step, by language
Each language is a mini SEO project. Here is the item breakdown for an EN/FR/DE migration. 2026 ballpark figures for London.
| Step | Scope | 2026 GBP range |
|---|---|---|
| International SEO audit | Multilingual crawl, hreflang mapping | 1,800 - 3,500 |
| Core technical migration | New platform, i18n | 4,500 - 9,000 |
| Per-language 301 redirects | Separate EN, FR, DE mapping | 3,000 - 5,500 |
| hreflang re-implementation | Tags + per-language sitemaps | 1,700 - 3,400 |
| Multilingual SEO QA | Per-market ranking tests | 2,200 - 4,400 |
| Monthly maintenance | Upkeep, monitoring | 900 - 2,000 / month |
The per-language 301 item is tripled: a distinct mapping per language, because localized URL structures differ.
Comparing per-language risks
The danger of a multilingual migration is that one language error contaminates the others. Here are the risks and their estimated impact.
| Risk | Cause | Estimated impact | Fix cost |
|---|---|---|---|
| Cross-language cannibalization | missing/wrong hreflang | -25 to -40% per market | 3,500 - 7,000 GBP |
| Per-language ranking loss | incomplete 301s | -30% language traffic | 2,200 - 4,500 GBP |
| Redirect loops | incorrect cross mapping | 404s + crawl budget | 1,100 - 2,800 GBP |
| Monolingual sitemap | missing per-language sitemap | partial indexing | 900 - 1,700 GBP |
A prior audit at 1,800-3,500 GBP avoids far costlier post-launch fixes and lost revenue on key markets.
Mini case study
Sarah, digital lead at an industrial SME in London, migrates an EN/FR/DE site of 180 pages generating 40% of its sales pipeline. Quote: international audit 3,000 GBP + migration 18,000 GBP + SEO QA 3,000 GBP = 24,000 GBP. Without correct hreflang, a -30% cannibalization on German traffic (her most profitable market) would have cost about 9 leads/month. At 1,000 GBP margin per contract (12% conversion), that is 1,080 GBP of lost monthly margin on the DE market alone. The audit pays for itself in under three months of protected traffic.
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FAQ
Why is hreflang riskier in migration than in a new build?
In migration, old hreflang tags point to URLs that change. If re-implementation is not synced with the 301s, Google receives contradictory signals.
One 301 plan or one per language?
One per language: localized slugs differ (EN /products/, DE /produkte/), so mappings are distinct and must be tested separately.
How long to stabilize per-market rankings?
With correct hreflang and 301s, positions stay stable within 1-2 weeks. On error, per-market recovery takes 3 to 6 months.
Can we migrate languages in waves?
Yes, but hreflang must stay consistent at each wave. An orphan language without its counterpart triggers cannibalization.
Is the international SEO audit mandatory?
For a multilingual site generating pipeline, yes: it is the insurance against a -25 to -40% per-market loss.
Let's scope your project. Specify your languages, page volume and priority markets: we will price the audit, migration and per-language hreflang 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.
