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Software as a Service: What It Is and What It Is Not

Software as a service, usually shortened to SaaS, is a way of delivering software. Instead of buying a program and installing it on your own equipment, you subscribe to one that the vendor operates and you reach it over the internet. This page gives the definition, shows where SaaS sits among related terms, and lists the trade-offs plainly.

The core idea

Three features define the model. The software is hosted by the vendor. It is accessed through a browser or app. And it is paid for through a subscription, rather than a one-time purchase. Remove any of these and you are usually describing something else.

How it differs from installed software

With installed software, you own a copy, run it on your own equipment, and decide when to update. You are responsible for keeping it working. With SaaS, the vendor runs it for everyone, updates it on its own schedule, and you rely on the vendor for availability. Installed software can run without a network connection; SaaS generally cannot.

SaaS among the cloud service layers

People often hear three terms together:

1. Infrastructure as a service. You rent basic computing resources, such as servers and storage, and manage everything above them.
2. Platform as a service. You rent an environment for building and running your own applications, without managing the servers.
3. Software as a service. You rent a finished application.

Each layer hands more responsibility to the vendor. SaaS hands over the most. Cloud, by itself, only describes where something runs.

Who is responsible for what

In SaaS the vendor is responsible for the servers, the application's security, backups and keeping the service available. You are responsible for who has accounts, how they sign in, what data goes in, and what your staff do with it. Both sides must pay attention, and many problems arise when each assumes the other has handled something.

Advantages

• No installation or server maintenance.
• Updates and fixes arrive automatically.
• Access from any device with a browser.
• Costs spread over time rather than paid up front.
• Often quick to start, since there is nothing to set up on your side.

Trade-offs

• You depend on the vendor's availability and on your own connection.
• You do not choose when the product changes.
• Costs continue for as long as you use it.
• Your data lives on someone else's systems, so privacy and export matter.
• Heavy customization may be limited.

Common types by purpose

Hosted software exists for nearly every business function: accounting, customer records, project tracking, messaging, scheduling, email delivery, website building and more. The label tells you how it is delivered, not what it does.

When SaaS is not the right choice

If your data must stay on equipment you control, if you need to work without a connection, or if a one-time purchase with long-term stability matters more, installed software may suit you better. Some organizations use both, hosted tools for general work and installed ones for sensitive tasks.

Example: a law office leaves the backup disk

A small law office once kept a program on one office computer and a backup disk in a drawer. When the computer failed, the office lost a day restoring from the disk. The office then moved its case tracking to a hosted product. Staff now sign in from the office, from home or from court, without installing anything. The vendor runs the servers and keeps the backups.

The office still has jobs of its own. It decides who has an account, removes people who leave, checks that the sign-in has extra verification, and exports a copy of its records on a schedule it controls. The hosted product removed the drawer and the disk. It did not remove the need for the office to look after its own side.

Words that often appear nearby

• Subscription: the recurring fee that pays for access.
• Tenant: a customer's own space inside a shared system.
• Uptime: the share of time the service is available.
• Single sign-on: one login that opens several tools.
• Export: a copy of your data that you can keep outside the product.

Questions a first-time buyer often asks

Is my data safe? That depends on both the vendor's practices and your own account habits. What if the internet goes down? You will lose access until it returns, so ask about any offline features. Can I switch later? Usually, if you can export your data. What does it really cost? The subscription plus setup, training and administration. Will it change under me? Yes, over time, so read release notes. Asking these questions of any vendor will give you a clearer sense of what you are renting.

A very short history of the idea

Before hosted software, companies bought programs and ran them on machines in their own offices. As networks became dependable and browsers became capable, vendors began to run the software themselves and let customers reach it online. The commercial change was as important as the technical one: instead of a single purchase, customers paid a continuing fee for a continuing service. The details have developed over the years, and the core arrangement described on this page is still the one most people mean by the term.

Next steps

Continue with the guides on SaaS versus installed software, SaaS and B2B, hosted software for businesses and how the subscription model earns. The how it works page shows one hosted product explained step by step.

Updated October 2026