It is possible to translate apps created in Web Designer into multiple languages by using the Language feature. Users view apps in their own language if you have configured them. If you have not configured them, the user will see the UI in the Fallback language configured in the Region component.
As of version 5.6, Web Designer uses two-letter language codes instead of locale codes to simplify internationalization. For a complete list of language codes, see List of ISO 639-1 codes.
To internationalize the app:
While editing your app in Web Designer, in the Language menu at the top-right, select the language you want to provide alternative translations for. For example, fr for French.
In the Components panel, set the desired text settings for that locale. For example, change the Title setting of all components.
Click File | Save.