Despite the growing attention on the use of online scaffolding to enhance argumentation skills, there has not been a comprehensive review conducted in this specific area. There is a lack of understanding of both the current state of online scaffolding for acquiring argumentation skills and the specific research gaps that exist. This article presents a scoping review of 32 empirical studies, published between 2000 and 2023, that addressed online scaffolding in the context of argumentation skills. Overall, the review indicates that online scaffolding is generally associated with positive results in developing argumentation skills. Surprisingly, customisation of scaffolding was often neglected in online scaffolding designs. When it is applied, limited consideration was paid to contingency, fading and transfer of responsibility aspects in online scaffolding customisation designs. The authors discuss the implications of their findings in terms of the design for online scaffolding and share recommendations for further research.