Exotic Higgs decays (and Long-Lived Particles) at future colliders

In this contribution I have summarized the existing studies on exotic Higgs decays at current and future collliders. While the proton-proton machines would in principle be the best option due to their larger energies and luminosities, we have also seen that the phase space regions where the LHC and FCC-hh lose steam, namely, low X masses and low lifetimes provide a unique window of opportunity for both e −p and e +e − colliders. The latter two kind of machines have been only recently studied, and thus there is naturally a lot of room for improvement. We also stress that these kind of studies can help to optimize the detector design of future colliders.