This paper presents WAM Studio, an open source, online Digital Audio Workstation (DAW) that takes advantages of several W3C Web APIs, such as Web Audio, Web Assembly, Web Components, Web Midi, Media Devices etc. It also uses the Web Audio Modules proposal that has been designed to facilitate the development of inter-operable audio plugins (effects, virtual instruments, virtual piano keyboards as controllers etc.) and host applications. DAWs are feature-rich software and therefore particularly complex to develop in terms of design, implementation, performances and ergonomics. Very few commercial online DAWs exist today and the only open-source examples lack features (no support for inter-operable plugins, for example) and do not take advantage of the recent possibilities offered by modern W3C APIs (e.g. Au-dioWorklets/Web Assembly). WAM Studio was developed as an open-source technology demonstrator with the aim of showcasing the potential of the web platform, made possible by these APIs. The paper highlights some of the difficulties we encountered (i.e limitations due to the sandboxed and constrained environments that are Web browsers, latency compensation etc.). An online demo, as well as a GitHub repository for the source code are available. CCS CONCEPTS • Software and its engineering → Abstraction, modeling and modularity.