SaaS
Software as a Service
- Pronunciation
- SASS
In short
SaaS (software as a service) is software delivered over the internet as a subscription; users sign in while the provider runs, updates and secures it.
What is SaaS?
Instead of buying a license and installing software on your own computers or servers, you use it online: Gmail, Slack, Notion, Figma, Salesforce and GitHub are all SaaS. The provider hosts the application, stores the data, applies updates and handles backups, and customers usually pay per user or per month.
SaaS is the top layer of the cloud service models. Under IaaS you manage virtual machines and everything on them, under PaaS you deploy your own code to a managed platform, and under SaaS you manage nothing but your account, settings and data. Each step up trades control for convenience.
For the companies that build it, SaaS shapes the architecture. Most SaaS products are multi-tenant: one running system serves many customers, with each customer's data kept separate. Recurring revenue, gradual feature rollouts, uptime commitments in SLAs and metrics such as churn and monthly recurring revenue all follow from the model.
A common misconception is that SaaS means the provider is fully responsible for security. Under the shared responsibility model, the provider secures the service, but customers are still responsible for who has access, strong authentication, configuration and the data they put in.
Key takeaways
- SaaS is software used over the internet as a subscription.
- The provider hosts, updates, secures and backs up the application.
- It is the top layer above PaaS and IaaS, with the least to manage.
- Most SaaS products are multi-tenant: one system serves many customers.
- Customers still own access control, configuration and their data.
Readers ask
What is the difference between SaaS, PaaS and IaaS?
IaaS gives you raw infrastructure, such as virtual machines and networks. PaaS gives you a platform to run your own code without managing servers. SaaS gives you a finished application. You manage less with each step up.
What are examples of SaaS?
Gmail, Microsoft 365, Slack, Zoom, Notion, Figma, Salesforce, Shopify and GitHub are all used as SaaS: you sign in and use them without installing or running servers.
What does multi-tenant mean?
One running instance of the software serves many customers, called tenants, while keeping each one's data and settings separate. It lets SaaS providers run efficiently and update everyone at once.
See also
- PaaSDevOps & Cloud, p. 40PaaS (platform as a service) is a cloud model where you deploy your code and the provider runs everything under it: servers, operating systems and scaling.
- IaaSDevOps & Cloud, p. 27IaaS (infrastructure as a service) is a cloud model where you rent virtual machines, storage and networks on demand and manage the OS and above yourself.
- Cloud ComputingDevOps & Cloud, p. 10Cloud computing is the on-demand delivery of computing resources, such as servers, storage, and databases, over the internet with pay-as-you-go pricing.
- SLADevOps & Cloud, p. 50An SLA (service level agreement) is a provider's commitment to customers about the level of service, such as 99.9% uptime, and what happens if it isn't met.
- ServerlessDevOps & Cloud, p. 47Serverless is a cloud model in which the provider runs your code on demand, manages all the servers, scales automatically, and bills only for actual use.
- APIBackend & APIs, p. 2An API is a set of rules that lets one piece of software request data or actions from another in a predictable, documented way.
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