This work reviews the capabilities of cathodoluminescence spectroscopy to monitor several key performance indicators in GaN-based High Electron Mobility Transistors (HEMTs) manufacturing. In particular, high throughput threading dislocation (TD) density measurements in the 10 8 -10 9 cm -2 range are presented, together with dislocation type discrimination capabilities. Beyond these applications, other relevant topics such as buried AlGaN layers composition and Mg dopant concentration for normally off devices are introduced.