As streaming video continues its meteoric rise, content monetization is becoming increasingly critical to rights holders and streaming service providers. This paper looks at the two major approaches to ad insertion – Client-Side Ad Insertion (CSAI) and Server-Side Ad Insertion (SSAI) – providing new insights into the two methods as well as outlining the key advantages and challenges for each. The paper also covers factors that should be considered when choosing CSAI or SSAI, and whether a combination of the two could be the optimal solution.