I'm trying to test my website with Selenium but I don't manage to change the language of the browser. I tried with Firefox, changing the profile also but it's not working. That's a pity because much of my content is changing regarding the language. Here is my Python code: @classmethod def setUpClass(cls): super(SeleniumTestCase, cls).setUpClass() options = Options() options.add_argument('--lang=en') cls.selenium = WebDriver(chrome_options=options) So normally I change the language but nothing happens... Just to clarify. I already checked on stackoverflow and if I post this question it's really because I tried most of the solutions I saw. Continue reading...