People living with dementia or cognitive impairment (PwD) and their carers often have unmet needs for informational and social support postdiagnosis. Web-based platforms have the potential to address these needs, although few have been developed for use by both PwD and carers. The CAREGIVERSPRO-MMD platform was developed to provide both user groups with informational and peer-to-peer social support. Platform logging data were analyzed to assess the extent to which PwD (n = 37) and carers (n = 37) engaged with the platform and its social/informational features in their daily lives. Participants also provided feedback on the usefulness and usability of the platform. The majority of PwD and carers found the platform and its social/informational features useful and usable, and significant subsets of both groups utilized the platform regularly. However, carers engaged with the informational and social features to a greater extent than PwD, and users highlighted that PwD typically required regular support to use the platform.