Solid matter that can rapidly and reversibly switch between adhesive and non-adhesive states is desired in many technological domains including climbing robotics, actuators, wound dressings, and bioelectronics due to the ability for on-demand attachment and detachment. For most types of smart adhesive materials, however, reversible switching occurs only at narrow scales (nanoscale or microscale), which limits the realization of interchangeable surfaces with distinct adhesive states. Here, we report the design of a switchable adhesive hydrogel via dynamic multiscale contact synergy, termed as DMCS-hydrogel. The hydrogel rapidly switches between slippery (friction ~0.04 N/cm²) and sticky (adhesion ~3 N/cm²) states in the solid-solid contact process, exhibits large span, is switchable and dynamic, and features rapid adhesive switching. The design strategy of this material has wide applications ranging from programmable adhesive materials to intelligent devices.