JavaScript is enabled by default in Firefox. However, some websites may display a message saying that JavaScript is required or ask you to make sure that JavaScript is enabled, which can make it seem like JavaScript may not be working in your browser. In most cases, this happens because a content-blocking extension is interfering with JavaScript. In that situation, you may need to review your extensions, especially those related to privacy or ad blocking or JavaScript, by adjusting their settings or by temporarily disabling them to identify the issue. If you find that a specific extension is causing the problem, it's best to contact the developer or visit the extension's support page for help.