To rank well on both sides of the language border, a Belgian site needs three things: a complete version per language with its own indexable URL structure, correctly paired hreflang tags, and content written from the keywords actually typed in each language, not translated word for word. Raw machine translation, published without review, almost always does more harm than good.

The figures argue for bilingualism. According to the estimates compiled by Université Laval, the country has roughly 6.9 million Dutch speakers versus 4.7 million French speakers, broadly a market that is 60% Dutch-speaking and 40% French-speaking. And language is no detail: according to the “Can't Read, Won't Buy” study by CSA Research (8,709 consumers, 29 countries), 76% prefer to buy a product presented in their language and 40% never buy on a site that does not offer it.

For a Belgian SME, the calculation is quickly made: a French-only site ignores the majority of national purchasing power. Conversely, a sloppy Dutch version, riddled with Netherlands-Dutch phrasings, can scare off precisely the Flemish customers it was meant to win over.

One market, two audiences: what the language border changes for your visibility

Google does not serve “Belgium” as a single market: it serves queries, in the language they are formulated in. A site without a Dutch version will never appear for “boekhouder Antwerpen” or “tuinaanleg Limburg”, however good its French-language SEO.

According to the Market Monitor by Becom, the digital commerce federation, Belgians spent €17.4 billion online in 2024, a rise of 6.7% in one year, spread over 179 million transactions. A majority share of these purchases is decided in Dutch: every page missing in one language is a closed shopfront for half the country.

One bilingual site or two separate sites?

For most SMEs, the answer is clear: a single .be domain with two language trees. This approach concentrates the domain's authority (inbound links, age, trust) instead of splitting it between two sites each starting from scratch. Two separate domains are only justified if brands, teams and offerings genuinely differ from one region to another. This decision is ideally made at the design stage: a point we systematically frame in our website creation in Belgium projects.

The technical structure that decides who sees which page

Which URL structure to choose for an FR/NL site?

Three options, which are not equal:

• Subdirectories (your-site.be/fr/ and your-site.be/nl/): the recommended solution for a Belgian site. A single domain authority, simple maintenance, clean tracking by folder.

• Subdomains (fr.your-site.be): technically valid, but they fragment the signals and complicate the setup with no real benefit for an SME.

• URL parameters (?lang=nl): to be avoided, hard to index, illegible, fragile for hreflang.

Golden rule: each page must exist at a stable, clean URL in each language. Sites that change language without changing URL are almost invisible to search engines, which index only one version.

The hreflang, that little attribute that avoids crossed pages

The hreflang tag tells search engines which version to serve to which audience: fr-BE for your French pages, nl-BE for the Dutch speakers. Without it, Google may show your French page to a Flemish user: first click, first disappointment, first step back.

The black spot: almost no one implements it correctly, and the mechanism is unforgiving. A single incorrect annotation can be enough to have the entire page group ignored.

The most frequent errors:

• Missing return links: the FR page declares the NL page, but not the reverse. Without reciprocity, the tags are ignored.

• Incorrect codes: be-fr (country before language) instead of fr-BE, or an invented code.

• Forgotten self-reference: each page must also declare itself.

• Pointing to redirected or error pages: each declared URL must respond directly and be indexable.

Translating or localising: the machine-translation trap

Flemish and Netherlands-Dutch: the same language, not the same vocabulary

It's the most underestimated trap: machine-translation tools are trained on Netherlands-Dutch, and a Flemish reader spots it within seconds. In Flanders, people say GSM, not “mobieltje”; solden, not “uitverkoop”; a frigo, not “koelkast”. A text riddled with Netherlands-Dutch phrasings sounds foreign to the audience it was meant to convince.

The nuance also applies to register: Netherlands-Dutch uses informal address readily, where Flemish commercial communication favours a more measured form. Localisation by a native Flemish speaker settles these details the machine does not see.

What does Google think of raw machine translation?

Google's anti-spam policies explicitly cite text translated automatically and published without human review as an example of content equivalent to spam. The risk is not only commercial, it is algorithmic: a Dutch version mass-translated and never reviewed can drag the whole domain down.

Best practice: machine translation as a first draft, then post-editing by a native Flemish speaker who adapts terminology, tone and examples.

Different keywords on each side of the border

Translating a keyword is not researching a keyword. The French speaker types “comptable Bruxelles”; their Flemish counterpart types “boekhouder”, not “accountant”, which rather refers to the certified chartered accountant. A construction company will target “maison clé sur porte” in French, but “sleutel-op-de-deur woning” in Flanders: the literal translation would give a phrasing no one searches for.

Volumes, competition and intent also differ from one language to another: some queries heavily contested in French are almost open in Dutch, and vice versa. That's an opportunity: run keyword research separately in each language.

The five-step method:

1. List the French queries that already bring you customers (positions, clicks, conversions).

2. Have the real Dutch equivalents established by a native speaker, not by a machine translator.

3. Check the volumes and competition of each NL query before producing the content.

4. Write fully fledged Dutch pages: title, meta description, subheadings and examples designed for Flanders.

5. Track your positions separately by language, a dashboard per tree.

Frequently asked questions

My site is only in French: where do I start to make it bilingual?

Start with your most profitable pages: the five to ten pages that generate your quote requests. Have them localised into Dutch, place them in a clean /nl/ tree with hreflang, then expand section by section, measuring as you go.

Is machine translation with human review acceptable for SEO?

Yes, provided the review is real: a native speaker who adapts Flemish terminology, tone and examples, not a simple spelling correction.

Should the blog be translated too, or only the service pages?

The service pages first: that's where conversion happens. For the blog, a few original Dutch articles, designed for Flemish queries, are better than a systematic translation of French articles targeting keywords no one types.

Is an English version useful for a Belgian site?

Rarely a priority for a local business: your customers search in French or Dutch. English is justified for international B2B, export or Brussels institutions. When in doubt, invest first in a flawless Dutch version: the return is almost always higher.

Priority action plan

1. Audit your visibility by language: positions, traffic and conversions of the FR queries, an inventory of what is missing on the NL side.

2. Choose a subdirectory structure (/fr/ and /nl/), a stable, indexable URL per page and per language.

3. Have localised your strategic pages by a native Flemish speaker: Belgian terminology, adapted tone, local examples.

4. Research the real Dutch keywords before writing: volumes, competition and intent, language by language.

5. Implement the hreflang (fr-BE, nl-BE, self-reference, reciprocal return links) and check it with an audit tool before going live.

The Belgian market rewards companies that take its linguistic reality seriously. A well-structured bilingual site not only doubles your audience: it places you on often less-contested Dutch-language queries, with a level of rigour that most of your competitors have not yet reached. The language border is not an obstacle; handled well, it's a competitive advantage.

Are you considering a Dutch version of your site? NTO Digital supports Belgian SMEs with SEO on both sides of the language border: here's how we approach these projects.