software as a service

Software as a service (SaaS /sæs/) is a cloud computing service model in which a provider delivers application software to clients while managing the required physical and software resources. SaaS applications are accessed via either a web application or locally-installed software. Unlike other software delivery models, SaaS separates "the possession and ownership of software from its use." SaaS use began around 2000, and by 2023 was the main form of software application deployment.

SaaS products typically run on rented infrastructure as a service (IaaS) or platform as a service (PaaS) systems including hardware and sometimes operating systems and middleware, to accommodate rapid increases in usage while providing instant and continuous availability to customers. SaaS customers have the abstraction of limitless computing resources, while economy of scale drives down the cost. SaaS architectures are typically multi-tenant; usually they share resources between clients for efficiency, but sometimes they offer a siloed environment for an additional fee. Common SaaS revenue models include freemium, subscription, and usage-based fees. Unlike traditional software, it is rarely possible to buy a perpetual license for a certain version of the software.