Multi-platform products and services are becoming ubiquitous. Front-end applications are increasingly accessed from a variety of devices, from smartphones, to embedded touch panels, to web browsers. While “Code Once, Deploy Everywhere” has long been a motto for Qt, it has never been truer than today with the addition of two new major platforms, micro-controllers and the Web, thus enabling a variety of new use cases. Using a single concrete example, we will see how a Qt application can be built to target desktop, mobile, microprocessor and microcontroller based embedded systems, and web browsers, reusing most of the code. We will first go through the different elements to keep in mind through development to accommodate these very different platforms. Then, as it is not possible in most projects to write only cross-platform code, we will see what exactly might or must be platform-specific, and how Qt can help in this case. Finally, we will analyze the development breakdown to see what the true value of Qt is in this type of project.