SaaS vs PaaS vs IaaS
IaaS rents you virtual servers that you manage from the operating system up, PaaS runs your code on a managed runtime, and SaaS is a finished application you log in to. Choose IaaS for full control, PaaS to deploy without managing servers, and SaaS when you only need the software.
For founders and developers deciding how much of the stack to run themselves before choosing a host or a cloud platform.
knowledge
- Read time
- 4 min
- Sections
- 6
- Updated
- 14 Nov 2026
- Written by
- WebJi® team
Last editorial update: 14 November 2026. Prices follow the dated sources on this page; checkout confirms current charges.
SaaS, PaaS and IaaS in one line each
IaaS rents you virtual servers, storage and networks to run as you like; PaaS runs your code on a managed runtime; SaaS is a finished application you simply log in to. The three models differ in how much of the stack the provider runs for you.
- IaaS (Infrastructure as a Service): you install and patch the operating system, runtime and database on rented virtual machines.
- PaaS (Platform as a Service): you push code; the provider manages servers, operating system, scaling and TLS.
- SaaS (Software as a Service): nothing to deploy; you configure accounts and data in software the vendor operates.
These are the three service models in NIST Special Publication 800-145, The NIST Definition of Cloud Computing (Mell and Grance, September 2011), the definition most contracts and cloud certifications still use. NIST pairs them with five essential characteristics (on-demand self-service, broad network access, resource pooling, rapid elasticity and measured service) and four deployment models: private, community, public and hybrid cloud. The wider picture is in what cloud computing is.
Who manages what in SaaS, PaaS and IaaS?
The dividing line is the runtime: in IaaS you manage everything from the operating system up, in PaaS you manage only your application and data, and in SaaS you manage only users, settings and data.
| Layer | IaaS | PaaS | SaaS |
|---|---|---|---|
| Application code | You | You | Provider |
| Runtime and middleware | You | Provider | Provider |
| Operating system and patches | You | Provider | Provider |
| Virtualisation and host | Provider | Provider | Provider |
| Network, storage, power | Provider | Provider | Provider |
| Accounts, permissions, data | You | You | You configure; provider secures the platform |
Responsibility for data never leaves you. On every model you decide who can log in, what is stored and how long it is kept; a provider hosting the database does not take over your obligations to your customers.
Examples of IaaS, PaaS and SaaS
AWS EC2 and a Linux VPS are IaaS, Heroku, Render, Vercel and Google App Engine are PaaS, and Gmail, Zoho CRM, Canva and Shopify are SaaS. The list describes the layer each service sells, not a recommendation.
| Model | Examples | What you receive |
|---|---|---|
| IaaS | AWS EC2, DigitalOcean Droplets, a WebJi® Linux VPS | A virtual machine with root access, a network and a disk |
| PaaS | Heroku, Render, Vercel, Google App Engine | A deploy command and a running app with TLS |
| SaaS | Gmail, Google Workspace, Zoho CRM, Canva, Shopify | An account in software someone else runs |
Serverless functions (FaaS), such as AWS Lambda, are usually counted as a narrow form of PaaS: you upload a function, not an app. PaaS options for Indian developers are compared in Vercel alternatives in India.
When each cloud model is the wrong choice
Each model fails in a predictable way: IaaS when nobody will maintain the server, PaaS when the app needs something the platform does not expose, and SaaS when the vendor cannot meet your data or exit needs.
- IaaS is wrong when nobody on the team will patch an OS, read a log or restore a backup at 2 a.m. The bill is low; the unmanaged risk is not.
- PaaS is wrong when you need a custom kernel module, a raw TCP port, a long-running daemon or a filesystem the platform does not offer.
- SaaS is wrong when the vendor cannot meet your data-residency, integration or exit requirements, or when per-seat pricing outgrows a self-hosted equivalent.
Two smaller traps: a PaaS free tier that sleeps after inactivity is not production hosting, and a metered IaaS bill without budgets and alerts can outrun a fixed-price server in a quiet month. If you choose IaaS but want someone else on call, see managed vs unmanaged hosting.
Which model is cheapest, and how hard is it to switch?
SaaS is cheapest to start, IaaS is usually cheapest at steady scale, and the cheapest model at the start is often the most expensive one to leave. Compare the total bill including the hours someone spends maintaining it.
A team that starts on PaaS often moves to IaaS when a background worker, cron job or custom port appears, and that move means rebuilding deployments and backups. Choose for the next twelve months: if the product will need a queue worker and a tunable database, start on IaaS; if it is a frontend and a small API, PaaS is cheaper than the hours spent patching. Whatever you pick, keep code versioned, migrations scripted, backups off the host and configuration in environment variables, so a move is a deploy rather than a rebuild. Server sizing for SaaS products is in the SaaS hosting guide.
Frequently asked questions
Is a VPS IaaS or PaaS?
A VPS is IaaS. You get a virtual machine, root access and a network, and you install and patch the operating system, runtime and database yourself. A control panel on top changes the convenience, not the model.
Is Google Drive SaaS or IaaS?
Google Drive is SaaS: a finished application you sign in to. Raw object storage such as Amazon S3, where you build your own application on top of storage buckets, is generally treated as IaaS.
Which model should a small team start with?
Start with PaaS if the product is a web app with no background workers or custom ports, because it removes server maintenance. Start with IaaS when you need cron jobs, a queue worker, a tunable database or a fixed monthly bill.
Where do public, private and hybrid cloud fit in?
They are deployment models, a separate axis from SaaS, PaaS and IaaS. Any service model can run on a public cloud shared by many customers, a private cloud for one organisation, or a hybrid of the two, as NIST SP 800-145 describes.
Definitions checked against NIST SP 800-145 on 15 November 2026 · Reviewed by the WebJi® team, Jaipur.
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