Dementia-related behavioral and psychology symptoms (BPSD) are undertreated and have negative consequences. However, families do not have access to disease information, tailored problem-solving  and effective management strategies, and with COVID-19, are more socially isolated and distressed. To address this dementia care gap, we describe a Phase III efficacy trial testing an online platform, WeCareAdvisor, and design modifications necessitated by COVID-19. WeCareAdvisor provides caregivers with disease information, daily tips, and a systematic approach for describing behaviors, investigating underlying causes, creating tailored strategies, and evaluating their effectiveness (DICE). The trial will enroll 326 caregivers nationwide, randomly assign them to immediately receive WeCareAdvisor (treatment), or a 3-month waitlist (control) and evaluate short (1- and 3-month) and long-term (6-month) outcomes for caregiver distress with and confidence managing BPSD, and BPSD occurrences. We will also evaluate utilization patterns with different prompting conditions: high-intensity (telephone and email reminders), low-intensity (email reminders), or no reminders to use WeCareAdvisor. COVID-19 necessitated design modifications resulting in greater inclusivity of caregivers from diverse races, ethnicities, and geographic areas. Key modifications include shifting from in-home, in-person interviewing to telephone; adjusting tool functionality from operating on a grant-funded iPad to caregivers' personal internet-capable devices; and expanding recruitment from one metropolitan area to nationwide. Study modifications necessitated by COVID-19 facilitate national outreach, easier tool adoption, and enable more diverse caregivers to participate. This study addresses a critical dementia care need, and design modifications may shorten timeline from efficacy testing to commercialization.