  Recent advancements in 2D materials have revealed the potential of van der
Waals magnets, and specifically of their magnetic anisotropy that allows
applications down to the 2D limit. Among these materials, CrSBr has emerged as
a promising candidate, because its intriguing magnetic and electronic
properties have appeal for both fundamental and applied research in spintronics
or magnonics. Here, nano SQUID-on-tip (SOT) microscopy is used to obtain direct
magnetic imaging of CrSBr flakes with thicknesses ranging from monolayer (N=1)
to few-layer (N=5). The ferromagnetic order is preserved down to the monolayer,
while the antiferromagnetic coupling of the layers starts from the bilayer
case. For odd layers, at zero applied magnetic field, the stray field resulting
from the uncompensated layer is directly imaged. The progressive spin
reorientation along the out-of-plane direction (hard axis) is also measured
with a finite applied magnetic field, allowing to evaluate the anisotropy
constant, which remains stable down to the monolayer and is close to the bulk
value. Finally, by selecting the applied magnetic field protocol, the formation
of N\'eel magnetic domain walls is observed down to the single layer limit.
