Following vortices around When stirred, superfluids react by creating quantized vortices. Studying the dynamics of these vortices, especially in the strongly interacting regime, is technically challenging. Sachkou et al. developed a technique for the nondestructive tracking of vortices in thin films of superfluid helium-4. Their system contained a microtoroid optical cavity coated by a thin film of helium-4, in which vortices were created by using laser light. When imaging the subsequent dynamics of the vortices, the researchers found that coherent dynamics strongly dominated over dissipation. Science, this issue p. 1480 Quantized vortices are fundamental to the two-dimensional dynamics of superfluids, from quantum turbulence to phase transitions. However, surface effects have prevented direct observations of coherent two-dimensional vortex dynamics in strongly interacting systems. Here, we overcome this challenge by confining a thin film of superfluid helium at microscale on the atomically smooth surface of a silicon chip. An on-chip optical microcavity allows laser initiation of clusters of quasi–two-dimensional vortices and nondestructive observation of their decay in a single shot. Coherent dynamics dominate, with thermal vortex diffusion suppressed by five orders of magnitude. This establishes an on-chip platform with which to study emergent phenomena in strongly interacting superfluids and to develop quantum technologies such as precision inertial sensors. Nondestructive tracking of vortices in thin films of superfluid helium-4 finds that coherent dynamics dominate over dissipation. Nondestructive tracking of vortices in thin films of superfluid helium-4 finds that coherent dynamics dominate over dissipation.