  The characterization of the magnetic field distribution is essential in
experiments and devices that use magnetic field coil systems. We present an
open-source application software, MFV (Magnetic Field Visualizer), for the
visualization of the distribution of the magnetic field produced by circular
coil systems. MFV models, simulates, and plots the magnetic field of coil
systems composed by any number of circular coils of any size placed
symmetrically along the same axis. Therefore, any new design or well known coil
system, such as the Helmholtz or the Maxwell coil, can be easily modeled and
simulated using MFV. A graph of the homogeneity of the magnetic field can be
also produced, showing the work region where the magnetic field is homogeneous
according to a percentage of homogeneity given by the user. An standardized
input and output file format is employed to facilitate the exchange and
archiving of data. We include some results obtained using MFV, showing its
applicability to characterize the magnetic field in different coil systems.
Furthermore, the magnetic field results provided by MFV were validated by
comparing them with results obtained experimentally in a Helmholtz coil system.
