 Gauss's law for magnetism

Gauss's law for magnetism is $\nabla \cdot \mathbf{B}=0$. Its integral form says that the net magnetic flux through every closed surface vanishes, so the normal magnetic field is continuous across an ordinary interface.

Gauss's law for magnetism is one of the four Maxwell's equations, which are fundamental to electromagnetism. Specifically, Gauss's law for magnetism states that the total magnetic flux passing through a closed surface is zero.