Actions Builder and the Actions SDK both support localization of your Action. When you serve your Action in multiple languages, the user-facing content of your Action requires translation. For example, intents should have multilingual training phrases.
By default, your Action projects support the following:
Supports all regions (countries), as long as your users have set their Google Assistant device to a geographic region supported by Assistant and a language supported by your Actions project.
Uses a Text-To-Speech voice that corresponds to the user's Assistant locale. You can override this behavior and choose a specific TTS voice that doesn't change based on the user's Assistant locale.