  We investigated the spin dynamics by electron spin resonance (ESR) of the
Yb-based, effective spin-1/2 delafossites NaYbO$_{2}$, AgYbO$_{2}$,
LiYbS$_{2}$, NaYbS$_{2}$, and NaYbSe$_{2}$ which all show an absence of
magnetic order down to lowest reachable temperatures and thus are prime
candidates to host a quantum spin-liquid ground state in the vicinity of long
range magnetic order. Clearly resolved ESR spectra allow to obtain well-defined
$g$ values which are determined by the crystal field of the distorted
octahedral surrounding of the Yb-ions in trigonal symmetry. This local crystal
field information provides important input to characterize the effective $S =
1/2$ Kramers doublet as well as the anisotropic exchange coupling between the
Yb ions which is crucial for the nature of the groundstate. The ESR linewidth
$\Delta B$ is characterised by the spin dynamics and is mainly determined by
the anisotropic exchange coupling. We discuss and compare $\Delta B$ of the
above mentioned delafossites focussing on the low temperature behaviour which
is dominated by the growing influence of spin correlations.
