Glossary Updates6 new terms added to the glossaries · October 11, 2026, 13:38 CEST
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Glossary · 4 · Platform SDKs and extensions

Software as a service (SaaS)

Also known as: SaaS, Software-as-a-Service, Hosted software

In cloud computing, software as a service (SaaS) is a service model in which a provider runs an application on its cloud infrastructure and customers use it over a network, typically through a web browser or an API, without managing the underlying infrastructure, operating systems or the application itself apart from limited user-specific settings.

  • Platform SDKs

In one sentence

Software as a service (SaaS) is the cloud service model in which a provider runs an application and customers use it over the network.

Example

A company uses a hosted CRM in the browser and extends it with a custom app built with the vendor's platform SDK; the vendor operates and updates the application for all customers.

How it applies

  • Platform SDKs: Because SaaS customers cannot change the provider's code, providers offer extension SDKs, APIs, webhooks and marketplaces instead. Customizations live in extensions that the platform hosts, sandboxes and upgrades with it. The SDK defines what can be customized and what stays under the provider's control.
  • Developer SDKs: SaaS APIs are reached through client libraries; documentation covers authentication, rate limits, data residency options and the API's deprecation policy, since the provider changes the service on its own schedule.
  • Multi-tenancy: Most SaaS applications are multi-tenant; one version runs for all customers, and extensions must be built for an application that is updated without the customer's involvement.
  • Publishing SDKs: Hosted authoring tools, content delivery portals and documentation platforms are often delivered as SaaS and extended through their APIs.
  • Responsibility: In SaaS the provider operates the application; the customer remains responsible for its own data, user accounts and configuration. Contracts and the provider's documentation define the split; the service model itself does not make a use compliant.

SaaS vs. PaaS and IaaS

NIST SP 800-145 names three service models. With SaaS the customer uses the provider's application. With platform as a service (PaaS) the customer deploys its own applications on the provider's platform. With infrastructure as a service (IaaS) the customer runs its own operating systems and applications on provided computing, storage and network resources. See cloud computing.

External references