<p>A laser Doppler vibrometer is an interferometric sensor with broadband demodulation of the photodetector signal used to measure movements, vibrations and deformations that occur in biological and technical systems. These time-dependent displacements can span many orders of magnitude in velocity, frequency bandwidth and amplitude. The velocity of movement can vary from zero to hundreds of metres per second, frequencies can range from microhertz to gigahertz and displacement amplitudes can occur down to the femtometre regime. Huge structures with kilometre-scale dimensions may be analysed, or structures may have micrometre or even nanometre dimensions. The immense breadth of scale and the potentially inaccessible or extremely sensitive nature of these motions make them difficult to measure with traditional sensors but can be probed with laser Doppler vibrometry. This Primer gives a comprehensive overview of laser Doppler vibrometry with different methods and applications presented. Although a wide diversity of sensing solutions exists, the field still offers many research opportunities, for example, gigahertz vibrometry with resolutions in the attometre regime using squeezed light on nanostructures, fast tracking of moving targets or measuring on rapidly moving or extremely sensitive surfaces.</p>