  Cuprate superconductors still hold many open questions, in particular
concerning their normal state properties, including the role of charge
ordering. Nuclear magnetic resonance on $^{63,65}$Cu and $^{17}$O in the
CuO$_2$ plane is a very sensitive bulk probe of charge variations, but not
properly understood. Since early NMR, the oxygen satellite line splittings in
YBa$_2$Cu$_3$O$_{6+y}$ were attributed to the orthorhombic distortion, while
they could also be due to charge ordering. We employ high pressure NMR on
YBa$_2$Cu$_3$O$_{6.9}$ hoping that charge order would respond to pressure
differently than the chemical lattice. That is what we find, and we prove the
existence of charge ordering even at ambient conditions. As pressure increases
we can follow its local symmetry and amplitude as function temperature. Our
finding differ from what has been reported with other techniques so far, but
also show similarities that will be discussed. We also offer evidence from
literature NMR data that this charge ordering is ubiquitous to the CuO$_2$
plane.
