Libervia is a versatile XMPP client with multiple frontends, developed using Python. The web frontend, inclusive of browser code, is uniquely crafted in Python, leveraging Brython. In this talk, I will delve into Brython's essentials – a Python implementation in JavaScript. I'll discuss the rationale behind choosing Brython and demonstrate its application in enabling functionalities like instant messaging, blogging/social networking, video calling, and so on. Utilizing Brython facilitates code reuse across backend and frontend, eliminating the need for language and context switching. This approach significantly enhances overall development efficiency. Furthermore, employing Python in the browser, as enabled by Brython, introduces exciting possibilities. It simplifies the development process and broadens the scope for innovative features and interactions within web applications.