Adding French after launch costs three to six weeks of rework. What bilingualism demands of your data model, your interface and your documents.
A translated product is a product designed in one language with the strings swapped out. It shows immediately, and for reasons that have almost nothing to do with translation quality.
Layout.
French runs 15 to 20% longer than English on average. A button drawn for Save receives Enregistrer. Navigation calibrated on Settings receives Paramètres. Labels overflow, get clipped, or wrap to two lines and break the alignment — on mobile first.
Data, not only the interface.
A product name, a category, a cancellation policy, a transactional email: these are data. If your products table has a name column, you have a monolingual product with a translated interface. Adding the second language means migrating the schema, rewriting the queries and redoing search indexing. That's where the three to six weeks of rework live.
Formats.
Dates, numbers, currencies, alphabetical sorting, addresses, phone numbers. A sort that ignores accents places Étienne after Zoé. A Quebec user notices, and draws a conclusion about how serious the product is.
Documents and support.
Terms, policy, invoices, automated emails, customer service replies. That's where most “bilingual” products give themselves away: interface in French, invoice in English.
What the law requires in Quebec.
This isn't only a quality question. For a product offered in Quebec, French must be available on terms at least as favourable as any other language — that covers the interface, but also contracts of adhesion, invoices and commercial communications. A contract of adhesion must be presented in French before another language can be chosen.
The French version can't be the second one, nor the one that arrives next sprint.●
Five decisions for week 1.
Is language a property of the user or of the session? Should a user who switches language find that choice on another device? If so, it's a database column, and an explicit fallback rule.
What content is translatable? Distinguish three categories: the interface, user-created content, and regulatory content — mandatory in both languages. That distinction structures the data model.
What happens when a translation is missing? Show the default language, hide the field, or block publication? For regulatory content the answer is block. For a product description, probably show the original with a note. Decide once, apply everywhere.
One URL per language? With reciprocal hreflang tags. A single URL that switches language on a cookie is invisible to search engines in one of the two languages — and you lose half your ranking without seeing it.
And who validates the language? Machine translation reviewed by someone who doesn't work in that language produces text that is correct and wrong. Quebec business French isn't French from France: courriel not e-mail, magasinage not shopping. Name a validator per language, from the start.
The comparative cost.
Designed bilingual from the start, the premium sits around 10 to 15% of the interface budget — mostly design time to allow for length variation, and discipline about strings. Added after launch: schema migration, query rework, search reindexing, revising every mockup, rebuilding the documents. The factor is three to five, and it grows with every month of accumulated content.
What we don't do.
We don't ship an interface where French was dropped into components drawn in English. If the longest label doesn't fit the component, the component changes — not the word.