Internationalization / locales

Hi, is there a guide or resource on how to handle internationalization i18n in the _locales folder? I am trying to understand if the syntax is similar to Chrome’s guide (

Specifically, I wanted to know how to handle the locale formatting. For example, Chrome requires zh_CN, zh_TW, while other sites use zh, and zh-TW. Is there a guide for this? I spent time searching and did not find it. Thank you


Do what Chrome docs says and it will work just fine also in Firefox, they both uses underscore.

Great, thank you for the link and quick reply