Most French courses, apps included, teach Metropolitan French, specifically a fairly standard Paris-region register. That's a reasonable default, but it means a learner who's only ever studied app-French can open a Quebec news site or a Belgian newspaper and hit vocabulary that never came up in any lesson, not because it's advanced French, but because it's regional French the course simply didn't cover.
Numbers: Belgium and Switzerland diverge from France and Quebec
This is the most immediately practical difference. In France and Quebec, 70, 80, and 90 are constructed compositionally: soixante-dix (sixty-ten), quatre-vingts (four-twenties), quatre-vingt-dix (four-twenty-ten). In Belgium (and Switzerland), these have simpler dedicated words: septante (70), and in Switzerland huitante (80), with nonante (90) used in both Belgium and Switzerland. Quebec follows the French system for numbers despite its other regional differences.
If you've only ever practiced the standard French number system, seeing septante or nonante in a Belgian news article can genuinely stop you, not because the number is hard, but because it's a word you were never taught exists.
Everyday vocabulary that shifts by region
Quebec French carries a distinct everyday vocabulary shaped by its separate development and English-language contact, but often resolved with different French coinages rather than English loanwords, unlike the borrowings common in Metropolitan French. Common examples: magasiner (to shop) where France uses faire du shopping or faire les courses; char, informally, for car, alongside voiture; and courriel, a deliberately coined French alternative to email that's used more consistently in Quebec than in France, where email itself is common in everyday use.
Belgian French vocabulary overlaps heavily with Metropolitan French but includes its own regionalisms: dringuelle for a tip (France: pourboire), spéculoos as a specific regional pastry term now widely known even outside Belgium, and septante/nonante as covered above. Belgian French also tends to retain some formality markers, like a more consistent use of the formal register, that vary from casual Metropolitan usage.
Metropolitan French itself isn't monolithic either. Regional expressions vary within France, and app-taught French tends to reflect a fairly neutral, broadcast-standard register that doesn't fully match any single region's everyday speech, including Paris's own informal register.
Why this matters more for reading than it did for your course
A course has to pick one variety to teach, and standard Metropolitan French is a defensible default because it's widely understood everywhere French is spoken. But real reading doesn't respect that choice. A Quebec news site, a Belgian paper, an African Francophone outlet, each will use the vocabulary and number conventions of its own region, and a learner who only recognizes the France-standard forms will hit unexpected words that have nothing to do with proficiency level and everything to do with which French they happened to be taught.
The practical fix isn't studying every regional variety in advance, which isn't a realistic use of time for most learners. It's recognizing, the first time septante or magasiner stops you, that this isn't a gap in your French, it's a gap in which French you were taught, and noting the regional equivalent as you encounter it rather than assuming you've forgotten a word you never learned in the first place.
A short reference for the most common trip-ups
Beyond numbers and the examples above, a few other frequent regional swaps worth knowing: déjeuner means breakfast in France but lunch in Quebec (where breakfast is déjeuner in the older sense, closer to historical French usage, and dîner shifts similarly, meaning lunch in Quebec and dinner in France). This single pair causes real confusion in anything from restaurant listings to daily-schedule references, precisely because both words exist in both varieties, just mapped to different meals.
Cell phone terminology is another common trip-up: a mobile phone is un portable or un téléphone portable in France, while Quebec French favors un cellulaire, closer to the English-influenced coinage pattern common there. Weekend itself is le week-end in France, borrowed directly from English, while Quebec French more often uses la fin de semaine, a homegrown alternative avoiding the English loanword the way Quebec French frequently does compared to Metropolitan usage.
What this means for choosing what to read
None of this is a reason to avoid Quebec or Belgian sources while you're still building reading confidence. If anything, exposure to regional variation earlier rather than later prevents the surprise from feeling like a setback later on, when you assume your French should be further along than a single unfamiliar regionalism suggests. A practical approach: once you're comfortable with Metropolitan French news, deliberately read a Quebec or Belgian source on a topic you already understand well from French coverage. The shared topic gives you context to work out regional vocabulary from, rather than hitting both new content and new regional words at the same time.