The ultra-rare $K\rightarrow\pi\nu\bar{\nu}$ decays are considered golden modes in flavour physics. The charged $K^{+}\rightarrow\pi^{+}\nu\bar{\nu}$ decay mode is under investigation by the NA62 fixed-target experiment at CERN.
NA62 collected the world's largest dataset of charged kaon decays in 2016-2018, leading to the first measurement of the branching ratio BR($K^{+}\rightarrow\pi^{+}\nu\bar{\nu}$) based on 20 signal candidates. This provides evidence for the ultra-rare $K^{+}\rightarrow\pi^{+}\nu\bar{\nu}$ decay, observed with a significance of $3.4\sigma$.
NA62 restarted operation in 2021, and will continue taking data until CERN long shutdown 3, with the main goal of improving the precision on the measurement of BR($K^{+}\rightarrow\pi^{+}\nu\bar{\nu}$).
The search for the neutral $K_{L}\rightarrow\pi^{0}\nu\bar{\nu}$ mode is currently being addressed by the KOTO experiment, located at the J-PARC accelerator complex in Japan. KOTO is expected to reach the Standard Model sensitivity for the $K_{L}\rightarrow\pi^{0}\nu\bar{\nu}$ decay in three to four years of data taking.
The status of and prospects for
$K\rightarrow\pi\nu\bar{\nu}$ measurements at NA62 and KOTO experiments are reviewed.