SaaS is the top layer of cloud computing and is typically built on top of the solution given by PaaS. SaaS uses the web to deliver software applications, which are managed by third-party vendors, to end users. Thus, it's the most popular cloud service for consumers because it reduces the cost of software ownership by removing the need for technical staff to manage the installation, upgrades, and licensing of the software.

The service is typically charged on a per-user or per-month basis and provides the flexibility to add or remove users at runtime without additional costs. Office 365, Google Apps, DropBox, and OneDrive are some well-known examples of SaaS.