I keep hitting the "something's using port 3000" thing constantly with side projects running in parallel, and I used to just run lsof -i and squint at PIDs to figure out what was safe to kill. Port Radar sits in the menu bar and just tells you in plain English, which process, spun up by which app, and whether it's actually safe to stop. The on-device explanation is the part that matters most to me since I didn't want yet another background process phoning home about what I'm running locally.