SaaS

SaaS (Software as a Service) is a delivery model in which an application runs on the provider's cloud infrastructure and users access it remotely — most often through a web browser — on a subscription. The customer does not buy a perpetual licence or install anything locally; they pay for access, while the provider maintains the entire technical stack.

How the SaaS model works

In the traditional model a company bought software, installed it on its own servers and handled updates, backups and security itself. SaaS shifts those burdens onto the provider. The application is usually multi-tenant: a single instance serves many customers, whose data is logically isolated from one another. The provider is responsible for availability, scaling under load, patching vulnerabilities and rolling out new features that reach all users without any manual upgrade.

Billing is typically a subscription — monthly or annual — often tiered by number of users or feature scope. Integration with other systems happens through an API, and reliability is underpinned by a high availability architecture on the provider's side.

Practical application

The SaaS model dominates many software categories: email and office suites (Google Workspace, Microsoft 365), CRM (Salesforce), messaging (Slack), project tools and invoicing systems. For a business it means a lower barrier to entry (no large hardware investment), predictable costs and access from any device. It is worth remembering the trade-offs, though: dependence on the provider, questions of data location and regulatory compliance. SaaS is the most "ready-made" tier of the cloud — unlike IaaS and PaaS, where the customer builds the application on the supplied infrastructure or platform.