Most major web browsers let users modify their experience through extensions or add-ons. Extensions are bits of software that you can add to your browser to customize it or add functionality. Extensions can do all kinds of fun and practical things like enabling new features, foreign language dictionaries, or visual appearances and themes.
绝大多数主流 Web 浏览器都允许用户通过扩展或附加组件来改善使用体验。扩展是一类为浏览器添加功能或进行其他定制的“软件”。扩展可以做到很多有趣又实用的事情，例如启用新功能、查询外语词典、更换视觉外观或主题。