Spatiotemporal metasurfaces are analyzed from an information perspective, in which two information transition mechanisms on group extension and independent control of multiple harmonics are revealed and characterized. The information transition efficiencies of these mechanisms are analyzed as well, which could be used to predict the channel capacity of the spatiotemporal metasurfaces for wireless communications. The presented framework and gained results would be helpful to lay the groundwork for information-based spatiotemporal metasurfaces.