Recent results from rare flavour decays searches achieved using proton-proton collision data at $\sqrt{\mathrm{s}}=13$ TeV by ATLAS and CMS are presented. They include the studies of $B^{0}_{\mathrm{(s)}}\to\mu^{+}\mu^{-}$ decays carried out by both experiments and the first observation of the $\eta\to4\mu$ double Dalitz decay by CMS using Run 2 data. The trigger strategies allowing for rare decays searches involving soft muons in Run 3 are also discussed.