Language best practise

We have applications that are in dutch. What are the pro's cons or keeping the language on english, but writing your content in dutch? vs Changing the language to dutch? (we currently do both depening on the app, which is probably even worse, legacy things, so looking for a best practice moving forward) :D 
4 answers

There is quite a lot to this question, I prefer to develop in en_US (and leave that language in there)* name all the entities in en_US as well.

  • Development language and language used by users (content) are two separate things, you could have only Dutch users but still name entities, microflows in English
    • For future proofing your development process, I would advice to opt for English as development language. Even if your team is currently fully Dutch, will that still hold in 2-3 years?
    • What if you want to create generic components and publish it in the marketplace, it will need additional translations.
  • Marketplace modules provide at least en_US, (some even depend on it, which is imho an issue)
  • More consistency in your project (API's, external modules, custom code, logging) will almost always be in English
  • What content language you want to use, is up to each project to decide. It does not need to include en_US (even if that is your development language, just disable translation completeness checking for that language to avoid getting spammed with warnings)


*Mendix should offer the option to disable a language to users (e.g. en_US) but still have that language in Studio for development and consistency. If you delete a language it will delete every translation in that language, while Mendix already supports some sort of disabled languages: import a marketplace module with a language not in your project the additional language (e.g. es_US or es_MX) is still imported and translations exists.


Another thing to consider is the calculations based upon the locale setting (if only Mendix had the option to set a default locale...), i.e. date functions.

For example: if your language is set to en_US and you’ll want to retrieve the week number of a given date (i.e. 22-jun-2022), using formatDateTime, it will give you a week number based upon the en_US locale settings (so you’ll get week 26). If your language is set to nl_NL, it will give you the week number based upon the nl_NL locale settings, which will return week 25 for that same date. So the language setting has additional side effects which are not always evident.


Hi Jason,

The main problem I see with keeping the language on English but writing content in Dutch, is that you will have a problem if you decide to add English as a second language later on. 

Because of that I would always recommend to set the language to Dutch if you are writing content in Dutch. For projects that are already going for sometime I guess you will have to decide if there is a chance that you will add a second language and if it is still doable to actually add Dutch as a language and fill in all the captions. Most of the time it is probably not worth doing that work, unless you might add a second language.


In Java or Javascript code: I'd say that programming language-defined keywords and class names, function names, variables, database tables and columns should be in English, as accented characters like ç, é, è, ù may not get saved/interpreted correctly. And the decimal separator might not be the comma, for example – and date formatting issues.
Comments, technical specifications, protocols and documentation are probably better readable and maintainable when written in a native language.

But Mendix is a low-code platform and has a lot less of these challenges. When working with teams from other countries, the blocks and their code within can be hard to read in a native language.