A web application is a program you use through a web browser instead of installing it. Revenue’s myAccount is one. So is Gmail, the Daft.ie search, your bank’s online banking, and the booking page on Irish Rail. Nothing to download, nothing to update, and the same thing on your laptop as on your phone.
This guide explains what a web application is in plain words, with Irish examples, how one differs from a website and from an app on your phone, how it works underneath, and when a business needs one built. It’s written for someone who has been told “you need a web app” and wants to know what they’re being sold.
What is a web application?
The textbook version, from Wikipedia: “application software that is created with web technologies and runs via a web browser.” Amazon Web Services puts the two halves in one line: “A web application is software that runs in a web browser, with a backend running on a web server.”
The plain version is this. A website shows you things. A web application lets you do things, and remembers what you did. You log in, it knows who you are, it stores your data, and what you see changes depending on what you do. The page is the front of it; the real work happens on a server somewhere else.
Web application examples in Ireland and beyond
You use several every week without calling them that.
- Revenue myAccount and ROS. Revenue describes myAccount as the place to “manage your personal taxes online through PAYE services, MyEnquiries and more”, and ROS as where you “manage your own, or your client’s, current position with Revenue for various taxes”. Log in, file, pay, done, all in a browser.
- MyGovID. “A single account that lets you access government services in Ireland.” One login used by many government web applications.
- TFI Leap Card. Top up, register a card, set auto top-up, all on leapcard.ie.
- Irish Rail. The “Find Times and Buy Tickets” search on irishrail.ie is a web application sitting on a website.
- Daft.ie. A search over every property for sale and to rent in Ireland, used by “over 2.5 million users each month” according to Daft. The listing pages are the website; the search, saved searches and alerts are the application.
- Online banking. Every Irish bank’s online banking is a web application, with the phone app as a second door into the same system.
The global ones you’ll know: Gmail, Google Docs, Canva, Trello, the Shopify admin behind an online shop, WhatsApp Web, and ChatGPT in a browser. Is Facebook a web application? In a browser, yes. The Facebook app on your phone is a native app that talks to the same servers.
Website vs web application
The line is blurry, and most business sites are a bit of both. The useful test is whether the page changes for you.
| Website | Web application | |
|---|---|---|
| What it’s for | Telling people about you | Letting people do something |
| Same for everyone? | Yes | No, it depends on who’s logged in |
| Stores your data? | Rarely, beyond a contact form | Yes, that’s the point |
| Example | A plumber’s site with services and a phone number | The same plumber’s online booking and customer portal |
| Built with | WordPress, Webflow, Squarespace | Custom code, or WordPress with heavy custom development |
An online shop sits in the middle. The product pages are a website; the basket, checkout and your account are an application.
Web app vs native app vs progressive web app
A native app is the thing you download from the App Store or Google Play. AWS describes it as “a computer program that has been specifically designed for a particular user environment, such as a Windows desktop computer or an iPhone mobile device”, and notes that “unlike web apps, native apps, including mobile apps, are downloaded by the user to their device.” It can use the phone’s camera, notifications and offline storage more fully, and it costs more because you build it twice, once for iPhone and once for Android.
A progressive web app (PWA) is the halfway house. Mozilla’s developer documentation defines it as “an app that’s built using web platform technologies, but that provides a user experience like that of a platform-specific app.” Once installed it “gets an app icon on the device” and “can be launched as a standalone app, rather than a website in a browser.” But, as the same page says, PWAs “are, as a matter of technology, still websites.” For most Irish businesses that want “an app”, a PWA gives the icon on the home screen without the cost of two native builds.
How does a web application work?
Four parts, every time.
- The front end runs in your browser. It’s the buttons, forms and pages. AWS: “The client-side application deals with user interface functionality such as buttons and drop-down boxes.”
- The back end runs on a server. Mozilla’s description of its job is the clearest: “A Web Application’s job is to receive HTTP requests and return HTTP responses.” You ask for something, it works it out, it sends the answer.
- The database is where the data lives: accounts, orders, bookings, messages. Mozilla again: “Using a database allows the product information to be stored efficiently in an easily extensible, modifiable, and searchable way.”
- APIs connect the parts, and connect your application to other people’s. Mozilla defines an API as “a set of features and rules that exist inside a software program (the application) enabling interaction with it through software”. When a booking system takes a card payment through Stripe, or a quoting tool pulls an Eircode address, it’s using an API.
Modern web applications often load once and then update the page without reloading, which is why Gmail feels like a program rather than a series of pages. That design is called a single-page application, which Mozilla describes as “a web app implementation that loads only a single web document, and then updates the body content of that single document via JavaScript APIs such as Fetch when different content is to be shown.”
Types of web applications
Developers sort them by how they’re built. Business owners should sort them by what they do.
- Customer portals. Log in, see your account, your invoices, your documents. Accountants, letting agents, solar installers and clinics all end up wanting one.
- Booking and scheduling. Appointments, classes, courts, rooms. Takes payment, sends reminders, stops double bookings.
- Quoting and configurators. Pick your options, see a price, request it. Windows, kitchens, insurance, print.
- Ecommerce. Shopify and WooCommerce are web applications you rent or run; a custom shop is one you own.
- Internal tools and dashboards. Job tracking, stock, reporting, the spreadsheet that became a system.
- Software as a service. The product is the application, sold by subscription.
How do I open a web application?
Type its address into any browser, or click the link. You need three things: a browser (Chrome, Safari, Edge, Firefox), an internet connection, and if it holds your data, a login. There’s nothing to download. If a web application offers “Add to Home Screen” or “Install”, that’s the progressive web app version, and it puts an icon beside your other apps.
Are web applications secure?
As secure as they’re built. The industry’s reference list of what goes wrong is the OWASP Top 10, and the 2025 edition names, in order: Broken Access Control, Security Misconfiguration, Software Supply Chain Failures, Cryptographic Failures, Injection, Insecure Design, Authentication Failures, Software or Data Integrity Failures, Security Logging and Alerting Failures, and Mishandling of Exceptional Conditions.
You don’t need to understand all ten. You need a developer who does. Three questions sort them out: how do you make sure one customer can never see another customer’s data, how are passwords stored, and what happens when a payment or an upload fails. Vague answers to any of those are your answer.
When does a business need a web application?
When people keep ringing to do something they could do themselves. When staff re-type the same information into three places. When the spreadsheet has become the business. When customers ask “can I log in and see that?” Those are the signs, and none of them is “we should have an app”.
What decides the cost is not the number of pages but the number of things it does: how many kinds of user, how many screens each one needs, what it has to connect to (payments, accounts software, maps, email), and how much data has to be kept safe. A booking form with payment is a small job. A portal with three user roles, invoicing and an integration with your accounts package is a project. We build both on the same foundations as our web design and development work, and the first conversation is always about what the application has to do, not what it should look like.
Questions people ask about web applications
What is a web application with an example?
Software you use in a browser that stores your data and responds to you. Revenue’s myAccount is a good Irish example: you log in, it shows your tax position, you file and pay, all without installing anything.
What are the most used web applications?
By everyday use in Ireland: Gmail and Outlook on the web, Google Docs and Microsoft 365 online, online banking, Revenue myAccount and ROS, Daft.ie, Canva, ChatGPT, and the admin side of Shopify for anyone running a shop.
Is Facebook a web application?
Yes, when you use it at facebook.com. The Facebook app on your phone is a native app that connects to the same service.
What’s the difference between a web app and a website?
A website shows the same information to everyone. A web application changes depending on who you are and what you do, and it keeps your data. Most business sites are a website with a bit of application attached, like a booking form.
Do I need to download a web application?
No. It runs in the browser. Some offer an install option that adds an icon to your home screen, but that’s still the web version.
Can a web application work offline?
Partly. A progressive web app can cache pages and data so parts of it keep working without a connection, but anything that needs the server, like saving a booking, waits until you’re back online.
Sources
Wikipedia, Web application; Amazon Web Services, What is a web app?; MDN Web Docs on progressive web apps, the client-server overview, API and SPA; OWASP Top 10:2025; Revenue’s online services; MyGovID; Daft.ie. Read on 20 September 2026.
