What Is SaaS? Meaning, Examples and What It Takes to Build One

What is SaaS? SaaS, short for software as a service, is software you use through a browser or an app while the provider runs it on their own servers, keeps it updated and charges you for access, usually by subscription. You do not install it, patch it or back it up yourself. If you read your email in a browser, keep files in a cloud drive or take payments through an online shop platform, you already use SaaS every day. This guide explains the model in plain terms, shows how it differs from the other cloud models, looks at real examples, and covers the questions a business should ask before renting software or building its own SaaS product.

What is SaaS? A short definition

The most widely quoted definition comes from the US National Institute of Standards and Technology. In its definition of cloud computing (NIST SP 800-145), SaaS is the capability to use the provider's applications running on a cloud infrastructure, where the customer does not manage the underlying network, servers, operating systems or storage, and at most adjusts a limited set of user-specific settings.

In practice that means three things. First, the software lives in one place, run by the vendor, and every customer reaches it over the internet. Second, the vendor is responsible for availability, security patches, backups and new versions. Third, you pay for the right to use it for a period of time rather than buying a copy. Everything else, such as pricing per user, per seat, per location or per transaction, is a business decision layered on top of that model.

SaaS vs PaaS vs IaaS: who manages what

SaaS is one of three service models in the same NIST document. The difference between them is simply how much of the stack the provider manages for you:

• IaaS (infrastructure as a service): you rent virtual servers, storage and networks. You install and maintain the operating system and everything above it. Typical users are development and operations teams.
• PaaS (platform as a service): you deploy your own code onto a managed platform. The provider runs the servers, runtime and databases; you are responsible for your application.
• SaaS (software as a service): you use a finished application. The provider manages the whole stack, from hardware to the features you click on.

A useful way to remember it: with IaaS you rent a kitchen, with PaaS you rent a kitchen with a cook who follows your recipe, and with SaaS you order the meal. A SaaS company itself is often built on IaaS or PaaS underneath, which is why the three terms appear together so often.

How SaaS works behind the login screen

From the outside a SaaS product looks like a website with a login. Behind it, a few design decisions shape everything else.

One application, many customers

Most SaaS products are multi-tenant: one running application serves many customers, and each customer's data is kept separate by the software rather than by giving everyone their own server. This is what makes the model affordable, and it is also where the most serious engineering risk sits, because a single missing check can expose one customer's data to another. Single-tenant setups, where each customer gets an isolated instance, exist too and are common for larger or regulated clients.

Subscriptions, plans and limits

Billing is part of the product, not an afterthought. Plans decide which features, how many users or how much usage each customer gets, and the application has to enforce those limits, handle upgrades and downgrades, send invoices and react when a payment fails.

Continuous updates

Because there is only one version in production, the vendor can ship improvements and security fixes to every customer at once. The flip side is that customers cannot stay on an old version when they dislike a change, so good SaaS vendors announce changes early and avoid breaking existing workflows.

SaaS examples, and when a licence is the better deal

Familiar examples include office and email suites such as Google Workspace and Microsoft 365, CRM systems such as Salesforce, online shop platforms such as Shopify and team chat tools such as Slack. Many smaller, specialised products follow the same model for a single industry.

Our own products show both models side by side: Multi Score Screen, the live scoring software we build for sports venues, is sold as a monthly subscription based on the number of courts, with a lifetime licence per court for venues that prefer to pay once.

Our own Multi Score Screen is an example of the second kind: a cloud platform that manages courts, matches and live scores for sports venues and shows them on TVs, phones and referee tablets. It also shows that subscription is not the only option. As listed on our pricing page, venues can choose monthly plans or a one-time licence per court. Some customers prefer predictable monthly costs and included updates; others would rather pay once and own the right to use the software indefinitely. Offering both is a deliberate product decision, not a contradiction.

Advantages and risks for a business

SaaS is popular for good reasons, but renting software also means trusting a supplier with part of your operation. Weigh both sides:

• Fast start: you can sign up and use the product the same day, without servers or installation.
• Predictable running costs: the subscription covers hosting, maintenance and updates.
• Access anywhere: a browser and a connection are enough, which suits distributed teams.
• Dependence on the vendor: prices, features and terms can change, and the product can be discontinued.
• Data location and privacy: you need to know where data is stored and processed, and whether that fits the data protection rules that apply to you.
• Exit plan: check whether you can export your data in a usable format before you commit.
• Fit: a product built for thousands of customers will rarely match an unusual process exactly. Our guide on custom software vs off-the-shelf covers that decision in depth.

Choosing a SaaS product: questions to ask first

Before you sign up for a tool your business will depend on, ask the vendor, or check their documentation, for clear answers to these questions:

1. Where is our data stored and processed, and who at the vendor can access it?
2. Can we export all of our data, including files and history, in a standard format at any time?
3. What happens to our data after we cancel, and how long is it kept?
4. How are outages communicated, and is there a status page or a written service level?
5. Which integrations or APIs exist, so the tool can work with the systems we already use?
6. How are prices changed, and how much notice do customers get?

If a vendor cannot answer these questions in writing, treat that as information too. The same list works in reverse when you build a SaaS yourself: these are the questions your own customers will ask you.

Building your own SaaS: what drives the effort

If you plan to sell software as a service rather than buy it, the visible features are usually the smaller part of the work. Before estimating anything, list the foundations every SaaS needs:

1. Tenant isolation: a clear model for how each customer's data is separated, enforced in every query and every file download.
2. Accounts and access: sign-up, login, password reset, roles and permissions, and invitations for team members.
3. Billing: plans, trials, upgrades, failed payments, invoices and taxes for the countries you sell to.
4. Security: protection against the common web risks summarised in the OWASP Top 10, plus backups, logging and a tested restore procedure.
5. Operations: monitoring, error tracking, uptime alerts and a way to release updates without downtime.
6. Support and admin tools: an internal panel to look up customers, fix data and answer questions without touching the database by hand.

Cost depends on how many of these you need on day one and how complex your core feature is, so any price quoted without a scope is a guess. A sensible path is a minimum viable product: one well-defined problem, a small group of real customers and only the foundations listed above, then expand based on what customers actually use. That is the approach we follow in custom software development projects, starting with a short discovery phase that produces a written scope before any code is written.

Two choices deserve special care early on. The first is the data model for tenants, because changing it later means migrating every customer. The second is how you will deploy and update the product, because a SaaS is never finished: it is released continuously for as long as it has customers.

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