What Is SaaS? How Software as a Service Works

Software used to be something you bought, installed on a computer, and maintained yourself. Businesses purchased licenses, IT teams installed applications on individual machines or company servers, and major upgrades could become projects of their own.

SaaS, or Software as a Service, changes that model. Instead of installing and operating the software locally, you access an application over the internet while the provider runs and maintains the underlying service.

Gmail, Google Workspace, Microsoft 365, Dropbox, and Zoom are familiar examples. You open a browser or app, sign in, and use the service without needing to operate the servers, databases, deployment infrastructure, or update process behind it.

The basic model looks like this:

Traditional software

Buy software
     │
     ▼
Install locally
     │
     ▼
Manage infrastructure
     │
     ▼
Install updates
     │
     ▼
Maintain application


SaaS

Subscribe / sign up
     │
     ▼
Connect over internet
     │
     ▼
Use application
     │
     ▼
Provider operates and updates service

That shift—from owning and operating an installation to consuming software as an online service—is the central idea behind SaaS.

SaaS Means Software as a Service

SaaS is a software delivery model in which an application is hosted by a provider and made available to customers over the internet, matching the broader cloud service model described by NIST.

For the user, the experience can be remarkably simple:

Device
   │
   ▼
Internet
   │
   ▼
SaaS application
   │
   ▼
Provider-managed infrastructure

Instead of receiving software and becoming responsible for running it, the customer receives access to a functioning service.

Take email as a simple example. An organization could operate its own mail servers, install and configure the necessary software, manage storage, apply updates, monitor availability, handle backups, and maintain the surrounding infrastructure.

Alternatively, it can use a SaaS email service. Employees sign in and use email while the SaaS provider operates the systems behind it.

The software still runs somewhere. SaaS does not eliminate servers, databases, storage, networking, or maintenance; it changes who is responsible for them.

The provider operates the service, while the customer uses it.

The Software Is Hosted in the Cloud and Accessed Online

Most SaaS applications are cloud-hosted and accessed through the internet. Many run primarily in a web browser, although SaaS products can also provide desktop and mobile applications that connect to the same online service.

This makes the software much less dependent on one particular machine.

With locally installed software, the application and much of its data may live directly on a specific computer. Moving to another device can require another installation, transferring files, recreating settings, or dealing with licensing.

A SaaS application usually keeps the service and its important state remotely:

Laptop ─────┐
            │
Phone ──────┼────► Internet ────► SaaS service
            │
Tablet ─────┘

A user can therefore sign into the same account from different supported devices and access the same service and data.

Dropbox demonstrates this model clearly. Files are associated with an online service rather than existing only inside one local installation, so the same account can be used across computers, phones, and the web.

Google Workspace applies the same principle to productivity software. Documents, spreadsheets, email, calendars, and collaboration features are delivered through online services rather than requiring an organization to operate the complete application stack itself.

This accessibility is one of the reasons SaaS became useful to both individuals and businesses. The application follows the account rather than being tied entirely to one physical computer.

The Provider Manages the Software Behind the Service

The more important difference is on the operational side.

Running software involves much more than writing or installing the application. Someone has to provide compute resources, storage, databases, networking, monitoring, security updates, backups, deployment systems, and capacity.

In a SaaS model, much of that responsibility moves to the provider.

SaaS provider
     │
     ├── hosts application
     ├── operates infrastructure
     ├── deploys updates
     ├── performs maintenance
     └── scales the service
              │
              ▼
           Customer
              │
              └── uses application

This is why saying SaaS requires “no installation” needs a little qualification. Many SaaS products can be used entirely through a browser, but others offer optional or required client applications.

Zoom, Microsoft 365, and Dropbox, for example, can involve locally installed applications. They are still SaaS because the core service is provider-operated and delivered through an ongoing online relationship.

The distinction is therefore not simply installed versus not installed.

It is closer to customer-operated software versus provider-operated software service.

That difference becomes especially significant for businesses. An organization using SaaS does not normally need to deploy a new version of the application’s server software every time the provider releases an update.

The provider can update the hosted service centrally, and customers receive the new version through the service they already use.

SaaS Usually Uses Subscription Pricing

SaaS also changed how software is commonly purchased.

Traditional commercial software was often sold through a perpetual license. A customer paid a significant upfront price for a particular version and might later pay separately for upgrades, support, or maintenance.

SaaS commonly uses recurring subscriptions instead:

Traditional license

large upfront purchase
        │
        ▼
own/use that software version
        │
        ▼
possible paid upgrades


SaaS subscription

monthly / annual payment
        │
        ▼
continued access to service
        │
        ▼
updates delivered continuously

Subscriptions may be priced per user, per organization, by usage, by storage, through different feature tiers, or through a combination of those models.

For individuals, this can make sophisticated software accessible without a large initial purchase. A person may pay a relatively small monthly fee for storage, productivity tools, communication software, or another service.

Businesses can gain a similar advantage. Instead of purchasing infrastructure and large software licenses before knowing exactly how much capacity will be required, they can often begin with a smaller subscription and expand as usage grows.

That does not necessarily mean SaaS is always cheaper over its entire lifetime. Recurring subscriptions accumulate, and a large organization can spend substantial amounts on SaaS products.

The advantage is often lower upfront commitment and easier scaling, rather than a guarantee of lower total cost in every situation.

Familiar SaaS Products Show How Broad the Model Is

SaaS is not one particular category of application. It describes how software is delivered and operated.

Gmail is SaaS for email. Users access a provider-operated mail service rather than running their own mail infrastructure.

Google Workspace extends the model to productivity and collaboration, combining applications such as email, documents, spreadsheets, storage, and meetings around online accounts and shared data.

Microsoft 365 delivers productivity applications and cloud services through an ongoing subscription. Some applications can run locally, but they connect to provider-managed services for capabilities such as cloud storage, collaboration, synchronization, and account management.

Dropbox applies SaaS to file storage and synchronization. Zoom does the same for online meetings and communication.

The products are very different, but the delivery pattern is similar:

SaaS example	Service provided
Gmail	Email
Google Workspace	Productivity and collaboration
Microsoft 365	Productivity and cloud services
Dropbox	File storage and synchronization
Zoom	Video meetings and communication

These examples also show why “software in a browser” is an incomplete definition. Some SaaS applications are browser-first, while others have substantial desktop and mobile clients.

What connects them is the provider-managed service behind those interfaces.

Why Individuals and Businesses Use SaaS

For users, one of the largest benefits is convenience. There is usually less infrastructure to install and maintain, and updates can be handled centrally by the provider.

That makes getting started easier.

A small company that needs shared documents and email, for example, does not necessarily need to build an internal collaboration platform. It can create accounts with a SaaS provider and begin using an existing service.

The lower upfront cost can be equally important. Instead of buying servers and paying for a large software deployment before the first employee uses the system, the organization can often begin with a subscription appropriate to its current size.

SaaS can then scale with demand. A growing company may add users, storage, or higher service tiers without replacing the underlying infrastructure itself.

Automatic updates reduce another maintenance burden. Because the provider controls the hosted service, fixes and new versions can be deployed centrally rather than requiring every customer to manage a separate server upgrade.

Accessibility complements those benefits. Because the service is online, employees can often use it from different locations and supported devices without requiring the complete application and its data to exist on one office computer.

These properties explain why SaaS appears in both consumer and business software:

SaaS
 │
 ├── easy online access
 ├── lower upfront commitment
 ├── provider-managed updates
 ├── reduced infrastructure management
 ├── multi-device access
 └── ability to scale usage

The same trade also means depending more heavily on the provider. Customers rely on the service’s availability, pricing, security, data policies, supported features, and continued operation.

That is part of the SaaS model rather than an exception to it. Moving operational responsibility to a provider also means giving that provider more responsibility for whether the software remains available and usable.

SaaS Is Really a Shift in Software Ownership and Responsibility

The easiest way to understand SaaS is not to focus on whether an application opens in a browser or charges a monthly fee. Those are common characteristics, but neither captures the whole model.

The deeper change is the division of responsibility.

With traditional self-managed software, the customer receives software and assumes much of the responsibility for operating it. With SaaS, the customer consumes an application that the provider continues to operate as a service.

Self-managed software

Customer
  ├── installs
  ├── hosts
  ├── updates
  ├── maintains
  └── uses


Software as a Service

Provider
  ├── hosts
  ├── updates
  ├── maintains
  └── operates
          │
          ▼
Customer
  └── accesses and uses

That shift enables many of the characteristics associated with SaaS: online access, automatic updates, subscription pricing, lower upfront infrastructure requirements, easier scaling, and access from multiple devices.

It also explains why SaaS has become common across such different kinds of software. Email, file storage, office applications, communication platforms, accounting systems, customer-management tools, and countless other applications can all use the same delivery model.

SaaS means Software as a Service: software operated by a provider and delivered to customers over the internet as an ongoing service. Instead of installing and maintaining the complete system yourself, you access the application while the provider manages much of the infrastructure, updates, and maintenance required to keep it running.