What is a web app?

What a web app is.

A web app runs in a browser tab and is reached through an address, not an installer. The part you see is HTML, CSS and JavaScript that the browser downloads and runs. Whatever must outlast the visit usually lives on a server: saved records, accounts, uploaded files and the rules about who may change what. A small web app can skip the server and keep everything in the browser.

Compare a restaurant’s menu page with its table-booking page. The menu is a website: you read it and leave. The booking page is a web app: you pick a date, it checks which tables are free, and it saves your reservation where the staff can see it. Both open at an address in the same browser, often on the same site. The difference shows when you press a button. A web app takes your input, does something with it, and usually remembers the result.

• You open a web app at an address, with nothing to install first.
• It exists to get something done, not only to present information.
• The interface runs in the browser; shared records and permissions usually live on a server.
• Visitors load the current version, so a fix usually reaches people on their next visit.

Web app, website, or mobile app?

The lines blur. A website can contain a web app, such as a booking page on a restaurant’s site, and a progressive web app can be installed and launched like a mobile app.

Types of web apps.

These labels answer different questions, so one app can carry several. A booking system might be a full-stack, single-page, progressive web app at the same time.

Static web app

The server sends the same files to everyone, and all the work happens in the browser. Calculators, checklists and interactive guides fit here. What a visitor types stays in that browser unless the app sends it somewhere.

Full-stack web app

Adds server logic, a database and usually sign-in, so records are saved and shared across devices. Portals, trackers and booking systems need this, because one person’s change has to reach the next person.

Single-page app (SPA)

Loads one document, then swaps screens with JavaScript instead of loading new pages. Moving around feels quick, but navigation, saved state and visibility in search take extra care.

Multi-page or server-rendered app

The server sends a new HTML page for each screen. Search engines and link previews can read the content without running scripts, and pages stay partly usable if JavaScript fails.

Progressive web app (PWA)

A web app with a manifest, served over HTTPS, that browsers can offer to install with its own icon and window. Many also use a service worker so some screens open without a network.

Examples of web apps.

• Webmail in a browser tab: the inbox and folders live on a mail server, so the same messages appear on a laptop and a phone.
• A map in the browser that searches an address, loads the area you are viewing and draws a route between two points.
• Online banking, where balances come from the bank’s servers and each transfer asks you to confirm before it goes through.
• An online document editor that saves every change to your account instead of to a file on one computer.
• A booking page that checks which time slots are still free before it accepts a reservation.
• A customer portal where each client signs in and sees only their own projects, invoices and files.
• An inventory tracker a small shop updates during the day, so the count on screen matches the shelf.

Parts of a web app.

Interface

Screens, forms and buttons built from HTML, CSS and JavaScript that the browser downloads. Design each screen for a narrow phone, for the moment data is loading, and for a request that fails.

Server logic

Code that receives each request, checks the input and decides what to read or change. Rules that must hold for everyone, such as prices or availability, belong here and not only in the browser.

Database

The saved records, such as bookings, orders, notes and stock counts. A database keeps them after the tab closes and lets many people work from the same entries.

Sign-in and permissions

Sign-in establishes who someone is. Permissions decide which records that person may read or change, so one client never opens another client’s invoices.

Files and email

Photos, PDFs and attachments need file storage with the same access rules as the records they belong to. Email carries the confirmations and notifications the app sends.

Address and HTTPS

A domain people can type or bookmark, and a certificate so the browser trusts the connection. A progressive web app must be served over HTTPS before browsers offer to install it.

Common mistakes.

Expecting a static app to keep shared records

A static app has nowhere to store what one visitor enters for the next one. If people submit forms or work from a shared list, plan a backend and a database from the start.

Testing only the desktop view

Try narrow screens, keyboard navigation and the main action on a real phone before you share the address.

Treating sign-in as authorization

Check which records each account can read or change, including requests sent straight to the server rather than through the screens.

Showing key text only after scripts run

Some crawlers and link previews do not run JavaScript. Put titles, descriptions and key content in the HTML the server sends, and use scripts for interaction.

Building an app-store version before the workflow works

Prove the main task in the browser with the people who will use it. Installability or a platform-specific app can come later, once you know which screens matter.

In your App Cloud.

With Exepad you describe the web app you want, then create, refine, review and publish it in Studio. Published apps open in a browser, including on phones. A one-page site goes live on Free. An app with a database, authentication, email, file storage, or models and agents inside it needs a paid plan to go live, and custom domains need Pro. Model and service usage is metered separately.

Explore the capabilities or find an app or agent to create. Plan allowances and usage are explained on Pricing.

Web app questions.