IaaS vs PaaS vs SaaS: The Cloud Service Models, Layer by Layer
Every introduction to cloud computing eventually draws the same stack of boxes: IaaS, PaaS, SaaS. It looks like jargon, but it is really just one simple question repeated three times: how much of the stack do you want to manage yourself, and how much do you want someone else to handle for you?
Updated 2026-08-06
One stack, four ways to consume it
Running an application always requires the same stack of layers underneath it: physical hardware, an operating system, a runtime environment, and finally your actual application and its data. The only question is where the line gets drawn between "the provider manages this" and "you manage this."
IaaS — Infrastructure as a Service
IaaS gives you the raw building blocks: virtual servers, storage, and networking, with nothing installed on top. You get a blank virtual machine and decide everything from the operating system upward — what software runs, how it's configured, and how it's secured. It is the closest cloud equivalent to owning a physical computer, minus the physical computer.
IaaS suits teams who need maximum control and are comfortable managing servers — for example, running a custom application with very specific requirements that a pre-built platform doesn't support.
PaaS — Platform as a Service
PaaS hands you a ready-made platform for running your code, so you no longer manage the operating system, patching, or underlying servers at all. You upload your application, and the platform handles deployment, scaling, and infrastructure maintenance for you. You still write the application and configure it, but the "computer" underneath essentially disappears from your responsibilities.
PaaS suits developers who want to focus purely on building an application rather than operating servers — a huge share of modern web and mobile development happens this way.
SaaS — Software as a Service
SaaS is the layer nearly everyone touches daily without thinking about it: a finished application delivered entirely over the internet, with the provider managing absolutely everything underneath — servers, platform, and the software itself. Webmail, streaming services, and online office suites are all SaaS. You don't install anything or manage any infrastructure; you simply use the product through a browser or app.
A simple analogy: getting a meal
- On-premises is like buying groceries, cooking the meal yourself, in your own kitchen, with your own appliances.
- IaaS is like renting a fully equipped kitchen — you still cook everything yourself, but you don't own the stove.
- PaaS is like a meal-kit delivery — the ingredients and recipe are provided, you just do the cooking steps.
- SaaS is like ordering food from a restaurant — you simply receive the finished meal.
Why this matters
When you compare cloud providers or plan a project, "which service model do we need?" is usually the very first real decision — it determines how much your team has to build versus how much you get for free.