**Software as a service** (**SaaS**) is a [[Cloud computing|cloud computing]] delivery model in which software applications are hosted by a [[Service provider|service provider]] and made available to customers over the [[Internet|internet]], typically through a [[Web browser|web browser]], without requiring the customer to install, manage, or maintain the underlying [[IT infrastructure|infrastructure]] or [[Platform (computing)|platform]]. Under the SaaS model, the provider assumes responsibility for hosting, operating, updating, and securing the application, while customers access functionality on a [[Subscription business model|subscription]] or usage-based basis. SaaS is one of the three primary cloud service models alongside [[Infrastructure as a service|infrastructure as a service]] (IaaS) and [[Platform as a service|platform as a service]] (PaaS), and has become the dominant delivery model for a wide range of business [[Application software|applications]]. SaaS emerged from earlier concepts of [[Application service provider|application service providers]] (ASPs) in the late 1990s and gained widespread commercial adoption in the 2000s as [[Broadband internet access|broadband internet]] penetration increased and [[Multi-tenancy|multi-tenant]] cloud architectures matured. In a typical SaaS architecture, a single instance of the application serves multiple customers—or **tenants**—simultaneously, with data isolation maintained through logical separation rather than separate installations. This **[[Multi-tenancy|multi-tenant]]** model enables providers to achieve economies of scale in infrastructure and operations, delivering continuous updates and new features to all customers simultaneously without requiring individual deployments. Prominent SaaS applications include [[Salesforce]] for [[Customer relationship management|customer relationship management]] (CRM), [[Microsoft 365]] and [[Google Workspace]] for [[Productivity software|productivity]] and [[Collaboration software|collaboration]], [[ServiceNow]] for [[IT service management|IT service management]], [[Workday]] for [[Human resources|human resources]] and [[Financial management|financial management]], and [[Slack]] for [[Team communication|team communication]]. SaaS offers several advantages over traditional [[On-premises software|on-premises]] software, including reduced upfront capital expenditure, rapid deployment, automatic updates, and accessibility from any device with an internet connection. However, the model also introduces dependencies on provider uptime and [[Service level agreement|service level agreements]], potential concerns around [[Data privacy|data privacy]] and [[Data sovereignty|sovereignty]] when data resides in provider-managed environments, and reduced customization compared to on-premises deployments. [[Application integration|Integration]] with other enterprise systems is a common challenge, addressed through [[Application programming interface|APIs]], [[Integration platform as a service|integration platforms as a service]] (iPaaS), and pre-built connectors. The proliferation of SaaS applications within organizations has given rise to the discipline of **[[SaaS management|SaaS management]]**, focused on governing software procurement, license utilization, [[Shadow IT|shadow IT]], and security posture across an organization's SaaS portfolio.