What Is a Web Browser?

A web browser is the software you use to access the World Wide Web. Its job is to fetch web pages and other resources from servers across the internet and display them on your screen in a form you can read and interact with. Familiar examples include Chrome, Safari, Firefox and Edge. Although browsers feel simple to use, a great deal happens behind each page you open.

What a browser actually does

At its most basic, a browser is a request-and-display machine. You provide a web address, and the browser retrieves the resources at that address and presents them. It also manages the tools around that core task: tabs and windows, bookmarks, browsing history, a back button, and settings that control privacy and security. Modern browsers additionally run small programs within pages, allowing interactive applications such as maps, email and document editors to work inside the browser itself.

It is worth distinguishing the browser from the web and the internet. The internet is the underlying global network of connected computers. The World Wide Web is one service that runs on it — a vast collection of linked documents and applications. The browser is simply the program that lets you reach and view that web.

How a page is requested

When you type an address or follow a link, the browser first needs to find the server that holds the page. It does this through the Domain Name System, which translates a human-readable name such as example.com into the numerical address of a server. The browser then opens a connection and sends a request using the Hypertext Transfer Protocol, or HTTP, and its secure version, HTTPS.

The server responds by sending back the requested resource, typically an HTML document, along with any additional files the page needs, such as stylesheets, scripts, images and fonts. Each of these is usually a separate request. A single modern web page can involve dozens of such exchanges, all coordinated by the browser in the background, often within a fraction of a second.

Turning code into a page

Receiving the files is only the first step; the browser must then interpret them. This is the work of the rendering engine, sometimes called the layout engine, which sits at the heart of every browser. It reads the HTML and builds an internal model of the document’s structure. It reads the CSS to determine how each element should look, applying colours, fonts, sizes and positions. And it runs any JavaScript, which can change the page or respond to your actions.

From these ingredients the engine calculates the exact position and appearance of everything on the page — a process known as layout — and then paints the result on your screen. Because this happens continuously, the page can update as you scroll, click and type. Each element you see, and each hyperlink you can follow, is the visible outcome of this interpretation.

Security and privacy

Browsers carry significant responsibility for safety online. When you connect over HTTPS, the browser verifies the identity of the site using digital certificates and encrypts the data travelling between you and the server, so that others on the network cannot read it. A padlock icon in the address bar indicates such an encrypted connection.

Browsers also try to protect users from harm in other ways: warning about deceptive or insecure sites, isolating pages from one another so a malicious page cannot easily interfere with others, and offering controls over cookies and tracking. These defences are not absolute, which is why safe habits still matter, including caution around phishing and the use of two-factor authentication on important accounts.

Standards and choice

One reason the same website works across different browsers is that they all follow shared, published standards for HTML, CSS and related technologies. These standards are developed openly by organisations such as the W3C and the WHATWG, so that a page written once can be displayed consistently by any conforming browser. In practice, small differences remain, and web developers test their work across several browsers.

Because the browser is the gateway through which most people experience the web, the choice of browser affects speed, privacy and compatibility. Yet whichever one you use, its fundamental purpose is the same: to request resources from across the internet, interpret the code it receives, and turn it into the pages you read every day.