“The cloud” is everywhere in business technology, but the terms around it can be confusing. You’ll often see three acronyms: IaaS, PaaS, and SaaS. These describe the three main cloud service models, and understanding them helps you choose the right technology, control costs, and know who is responsible for what.
This guide explains each model in plain language, with examples, pros and cons, and tips for deciding which one your business needs.
What Is Cloud Computing?
Cloud computing means using computing resources — servers, storage, databases, software, and more — over the internet instead of owning and running them yourself. You typically pay for what you use, and the provider handles some or all of the underlying infrastructure.
The three service models differ in how much the provider manages and how much you manage.
The Pizza Analogy
A popular way to explain the models is with pizza:
- On-premises is making pizza at home from scratch — you handle everything.
- IaaS is buying ingredients and using a rented kitchen — you still do the cooking.
- PaaS is ordering a take-and-bake pizza — you just add toppings and bake.
- SaaS is eating at a restaurant — everything is done for you.
IaaS: Infrastructure as a Service
IaaS provides the basic building blocks of computing — virtual servers, storage, and networking — on demand. You manage the operating system, software, applications, and data, while the provider manages the physical hardware and data centers.
Examples
- Amazon Web Services (AWS) EC2
- Microsoft Azure Virtual Machines
- Google Compute Engine
- DigitalOcean Droplets
Pros
- Maximum flexibility and control in the cloud
- Scale resources up or down as needed
- No need to buy or maintain physical hardware
Cons
- Requires technical skills to configure, secure, and maintain
- You’re responsible for updates, patches, and much of the security
- Costs can grow unexpectedly without careful monitoring
Best for: IT teams that need full control, businesses migrating existing servers to the cloud, and custom or complex workloads.
PaaS: Platform as a Service
PaaS provides a ready-made platform for building, running, and managing applications. The provider handles the infrastructure, operating systems, and runtime environments, so developers can focus on writing code.
Examples
- Google App Engine
- Azure App Service
- AWS Elastic Beanstalk
- Heroku
- Managed database services
Pros
- Faster development and deployment
- Less infrastructure management
- Built-in scaling and tools
Cons
- Less control over the underlying environment
- Potential vendor lock-in if you rely on platform-specific features
- May not support every language or configuration
Best for: Development teams building web apps, APIs, and custom software who don’t want to manage servers.
SaaS: Software as a Service
SaaS delivers complete, ready-to-use software over the internet, usually through a web browser or app, on a subscription basis. The provider manages everything — infrastructure, platform, application, updates, and security of the service.
Examples
- Google Workspace and Microsoft 365
- Salesforce and HubSpot
- Slack and Zoom
- Accounting tools like QuickBooks Online and Xero
- Project management tools like Asana and Trello
Pros
- Ready to use with minimal setup
- No infrastructure or software maintenance
- Accessible from anywhere
- Predictable subscription pricing
Cons
- Limited customization
- Your data is stored with the provider
- Subscription costs can add up across many tools
- Dependence on the provider’s availability and roadmap
Best for: Most businesses for everyday tools like email, CRM, accounting, and collaboration. See our comparisons of project management software, accounting software, and CRM and SaaS solutions.
Side-by-Side Comparison
| Feature | IaaS | PaaS | SaaS |
|---|---|---|---|
| What you get | Servers, storage, networking | Platform to build and run apps | Finished software |
| You manage | OS, apps, data, security settings | Apps and data | Your data and user access |
| Provider manages | Physical infrastructure | Infrastructure, OS, runtime | Everything else |
| Control | High | Medium | Low |
| Technical skill needed | High | Medium | Low |
| Typical users | IT and infrastructure teams | Developers | Everyone |
The Shared Responsibility Model
Security in the cloud is a shared responsibility. The provider secures its infrastructure, but you are always responsible for some things, including:
- Your data and how it’s classified and shared
- User access — who has accounts and what they can do
- Account security, such as strong passwords and MFA (see 2FA methods ranked)
- Configuration of the services you use
With IaaS, you’re responsible for more — including operating system patches and network settings. Misconfigured cloud services are a common cause of data exposure, so review settings carefully.
Other “as a Service” Terms
- Serverless / FaaS (Function as a Service): Run code in response to events without managing servers.
- DBaaS (Database as a Service): Managed databases.
- BaaS (Backup as a Service): Managed backups — see cloud backup vs cloud storage.
- DaaS (Desktop as a Service): Virtual desktops delivered from the cloud.
How to Choose
- Need a ready-made tool for email, accounting, or CRM? Choose SaaS.
- Building a custom app and want to focus on code? Consider PaaS.
- Need full control or migrating existing servers? Consider IaaS.
- Consider your team’s skills — more control means more responsibility.
- Estimate total costs, including staff time, not just subscription or usage fees.
Most businesses use a mix of all three. For a closer look at major providers, see our cloud hosting comparison for enterprises and hosting types explained.
Frequently Asked Questions
Is web hosting IaaS, PaaS, or SaaS?
It depends. A cloud virtual server is IaaS, managed WordPress hosting is closer to PaaS, and hosted website builders are SaaS.
Which cloud model is cheapest?
There’s no single answer. SaaS has predictable subscription costs, while IaaS can be cheaper or more expensive depending on how efficiently you manage resources.
Is the cloud secure?
Major cloud providers invest heavily in security, but you must configure services properly and protect accounts. Most cloud security incidents involve customer-side mistakes, such as weak passwords or misconfigured storage.
Final Thoughts
IaaS gives you flexible infrastructure with maximum control, PaaS gives developers a ready platform to build on, and SaaS delivers finished software that’s ready to use. Understanding the differences helps you choose the right tools, estimate costs, and know your security responsibilities. For most small businesses, SaaS covers daily needs, while PaaS and IaaS become more relevant as you build custom software or scale your infrastructure.
This article is for general informational purposes. Services and features vary by provider.