Background Informal caregivers of people with dementia provide the majority of health-based care to people with dementia. Providing this care requires knowledge and access to resources, which caregivers often do not receive. We set out to evaluate the effect of online educational tools on informal caregiver self-efficacy, quality of life, burden/stress, depression, and anxiety, and to identify effective processes for online educational tool development. Methods We conducted a scoping review of articles on online educational interventions for informal caregivers of people with dementia searching CINAHL, MEDLINE, EMBASE, and PubMed from 1990 to March 2018, with an updated search conducted in 2020. The identified articles were screened and the data were charted. Results 33 articles that reported on 24 interventions were included. There is some evidence that online interventions improve caregiver-related outcomes such as self-efficacy, depression, dementia knowledge, and quality of life; and decrease caregiver burden. Common findings across the studies included the need for tailored, stage-specific information applicable to the caregiver’s situation and the use of psychosocial techniques to develop the knowledge components of the interventions. Conclusion We demonstrate the importance of having caregivers and health-care professionals involved at all stages of tool conceptualization and development. Online tools should be evaluated with robust trials that focus on how increased knowledge and development approaches affect caregiver-related outcomes.