Software as a Service (SaaS) is a cloud computing delivery model in which fully functional applications are hosted and maintained by a provider and delivered to users over the internet via a web browser or thin client, with the provider managing all underlying infrastructure, platform, and application layers. SaaS eliminates the need for local installation and enables subscription-based access with automatic updates, multi-tenancy, and built-in scaling. Prominent examples include Salesforce CRM, Microsoft 365, Google Workspace, Slack, and Zoom.
Overview
- Salesforce.com (1999) pioneered on-demand CRM as the first major SaaS company, establishing the subscription-per-seat business model.
- Google Apps (2006) and Microsoft Office 365 (2011) extended SaaS to productivity suites previously dominated by installed software.
- Modern SaaS products integrate via APIs and webhooks, forming ecosystems of interconnected services.
- Identity federation (SSO, SAML, OIDC) enables enterprise access control across SaaS portfolios.
- Data portability and vendor lock-in are persistent concerns requiring contractual and technical mitigation.
Key aspects
- Multi-tenant architecture: multiple customer organisations share infrastructure with logical data isolation.
- Automatic updates: provider deploys new versions transparently; users always access current version.
- Usage-based and seat-based pricing models predominate.
- SLA-backed uptime guarantees with transparent status pages.
- Integration platforms (Zapier, MuleSoft) connect SaaS products into business workflows.
Mechanisms
- Tenant isolation via database-per-tenant, schema-per-tenant, or row-level security in shared databases.
- Continuous deployment pipelines enable frequent feature releases without customer action.
- CDN and edge caching reduce latency for globally distributed user bases.
- RBAC and attribute-based access control manage authorisation within multi-tenant environments.
Applications
- CRM systems (Salesforce, HubSpot) for sales pipeline and customer data management.
- Communication platforms (Slack, Microsoft Teams, Zoom) for collaboration.
- ERP systems (SAP S/4HANA Cloud, NetSuite) for financial and operational processes.
- Security tools (Okta, CrowdStrike) delivered as managed services.
- AI writing assistants and code completion tools delivered via browser or IDE plugin.