Smart cities aim to address social issues in the community using Internet of Things (IoT). IoT has traditionally been used to address various challenges in different regions. Recently, efforts have focused on defining smart cities and addressing regional issues horizontally as they are often shared by other regions. There are two technological approaches to IoT services: the ‘vertical approach,’ which involves building unique IoT services tailored to regional characteristics, and the ‘horizontal approach,’ which enables new services by horizontally linking data collected in each region within City OS in the cloud. This paper categorizes technological approaches into three groups: ‘service-specific type,’ ‘cloud-intensive type,’ and ‘edge-cloud cooperation type,’ and compares their respective features.