In the years following the COVID‐19 pandemic, online assessment has emerged as an increasingly popular method for testing children. This review aims to review key advantages and disadvantages of online assessment in young children, specifically in the area of literacy and mathematics assessment. We first consider the recent history of online assessment and give evidence from our own experiences with online assessments in both Cebu, Philippines and Hong Kong. We then discuss the benefits of conducting assessments online. One of the key strengths of online assessments is the efficient use of resources, such as ease of staff training, increased participation and decreased costs for both participants and researchers. Difficulties related to testing environment, parental interference and exclusion of certain populations are also highlighted as focal challenges that must be considered when designing and implementing online assessment. The reliability and validity of online assessments are then specifically discussed in relation to the question of how to best ensure that online measures function as intended, stressing the importance of establishing separate norms for the various administration modes. Notably, online assessments delivered via phone screen must have separate norms than those delivered on a computer screen, as device differences may account for differences in performance. Finally, we present broader considerations for designing online assessments with young children. This includes practical tips for pilot testing, user interface design, data confidentiality and automatic scoring, both to enhance the efficiency of future online assessments and increase participation. Specifically, online assessments for children must account for their developing attentional abilities, meaning assessments should be brief, engaging and contain clear task instructions. The implementation of these considerations will support the development of more reliable, valid and inclusive assessments which will allow researchers and practitioners to support equitable and feasible online testing moving forward.