Web application

Content sourced from Wikipedia, licensed under CC BY-SA 3.0.

Web applications are programs that run in your web browser using web technologies. They began in the late 1990s when servers started generating dynamic responses instead of just serving static pages. Today, most web apps are hosted on remote servers and accessed over the internet, so you don’t install them on your device.

They rely on three main parts: the presentation (the browser), the application logic (the server), and storage (the database). The browser sends requests to the server, the server runs code and talks to the database, and then sends back pages or data for the browser to display.

Security is essential. Developers must plan for authentication, authorization, protecting data, handling input carefully, and keeping logs to monitor activity.

Web apps are built with frameworks that speed up development. Modern designs include single-page apps (SPAs) and progressive web apps (PWAs). SPAs load most of the app once and update the page without full reloads. PWAs use new browser features to work offline and can be launched from the home screen like native apps.

Many web apps run in the cloud as software as a service (SaaS). This makes it easier for providers to manage updates and billing, while users can run the app on lightweight devices because most work happens on the server.

Browsers isolate each tab for security, and you don’t need to install software. The same web code can work across devices with responsive design, so it stays usable on phones, tablets, and desktops. JavaScript, introduced in 1995, lets pages run dynamic features on the client, and Ajax, popularized in 2005, lets pages request data without reloading. Today, web apps often use JSON-based web APIs to communicate between client and server.

Architecturally, many web apps use a three-tier model: presentation in the browser, an application tier on the server, and a storage tier (the database). Some setups add an integration tier to simplify data access or move business logic into separate layers. A two-tier setup is also possible, but less common for larger apps.

Web app development is easier with frameworks that handle common tasks like user management. There’s also talk of Internet operating systems, though they’re not widespread yet.