You can auto-redirect store visitors to their preferred language based on their browser language settings if we support the matching (the list of supported language is available here).

To choose your preferred store languages, go to: Store > Settings > General > Store languages.
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Depending of your subscription plan you can select between 1 to 7 languages.

In the starter plan, you are limited to one store language of your choice.
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To modify your default locale language:

You can chose to translate your store in 2 languages of your choice.
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You unlock store translation in 7 languages:

Then, you can enable them by clicking on the switch button :