The advantages of HTML5 in web development include enhanced multimedia support, better semantic elements, and improved performance. HTML5 has built-in features for audio, video, and animation, eliminating the need for external plugins, thereby providing a more consistent user experience. The semantic elements improve the structure of web content, making it more accessible for search engines and screen readers. Additionally, HTML5 is designed for mobile responsiveness, allowing developers to create applications that function seamlessly across devices, improving engagement and usability.