iA Writer for Mac supports writing in many languages, and is localized in English, German, Japanese, French, Spanish, Italian, Russian, Chinese, Korean and Portuguese. At present languages such as Thai, Hebrew, and Arabic are not yet officially supported.
On macOS iA Writer will automatically use the system settings (Language & Region), however it is possible to designate a desired language for the app. To do so:
- Launch System Preference
- Navigate to
Language & Region
- Click ＋ (if iA Writer is not selected, select it from the list of apps)
- Select language from list of available localizations
You can learn more about this for your specific OS at the following Apple resource: