Mandatory caveat: beware of ground loops when using a USB oscilloscope! Most budget USB scopes share ground with your PC via the USB port. If you're probing high-voltage circuits (e.g., mains power, switching supplies), this can create a dangerous potential difference, risking damage to your computer or worse. Some scopes offer isolated inputs, but if yours doesn’t, use differential probes or an isolation transformer. Otherwise, you might end up debugging your laptop’s fried USB controller instead of your circuit.