We demonstrate the microwave signatures of individual Abrikosov-vortex penetration events in superconducting microwave resonators. $\lambda /4$ resonators with a narrowed region near the grounded end acting as a vortex trap were fabricated and studied using microwave transmission spectroscopy at millikelvin temperatures. Sharp stepwise drops in resonance frequency are detected as a function of increasing external magnetic field, attributed to the entry of individual Abrikosov vortices in the narrow region. This interpretation is confirmed by nitrogen-vacancy center magnetometry, revealing discrete vortex entry events on increasing field and the absence of such drops in a device with a wider narrowed region. Our results establish a method to investigate and manipulate the states of Abrikosov vortices with microwaves access and readout vortex configurations using magnetic-field sweeps and microwave drive.

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• Magnetic vortices
• Magnetometry
• Nitrogen vacancy centers in diamond
• Superconductivity
• Superconducting devices
• Type-II superconductors
• Microwave techniques