Web browser

• 1. Introduction

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  A web browser is the window through which roughly 5.4 billion people access the internet, yet most users have never thought twice about how one actually works. Type an address into a bar at the top of the screen, and within seconds a page appears. Behind that apparent simplicity is a chain of requests, encrypted connections, rendering engines, and cached resources that would have been incomprehensible to anyone alive just a few decades ago. How did this piece of software come to exist? Who built the first one, and who built the ones that conquered the world? And why, despite hundreds of options, do just a handful of browsers share almost everything between them?

• 2. How a Browser Works

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  Every browser session starts with a Uniform Resource Locator, the URL typed or pasted into the address bar. Virtually all URLs on the web begin with either http: or https:, which signals that the browser should use the Hypertext Transfer Protocol to retrieve the requested files from a web server. When the connection is secured via HTTPS, the exchange between the browser and the server is encrypted, protecting whatever passes between them from outside observation. Because of this role as a client making HTTP requests, a browser is technically classified as a user agent.

  Once the server responds, the browser receives a collection of raw materials: text, style sheets, images, and other multimedia files. These are handed to the browser's rendering engine, also called a layout engine, which processes them and converts them into the interactive visual page a person actually sees. Modern browsers run a second, separate engine alongside the renderer, one dedicated entirely to JavaScript. This division allows a page's visual structure and its dynamic behavior to be processed in parallel.

  Browsers also maintain an internal cache, a local store of previously downloaded resources such as large images. When a user revisits a page, the browser can pull those cached files from the device rather than fetching them from the server again, cutting load times noticeably. Cached items are only held as long as the web server's HTTP response messages specify, keeping the local store from growing stale. Pages also contain hyperlinks, each carrying its own URL, and clicking one simply starts the whole retrieval cycle over again.

• 3. From WorldWideWeb to Browser Wars

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  Sir Tim Berners-Lee created the first web browser in 1990, naming it WorldWideWeb. He quickly brought in Nicola Pellow to write the Line Mode Browser, a companion program that could display pages on dumb terminals without any graphical capability. For the next few years, the web remained a specialist tool.

  That changed in April 1993 with the release of the Mosaic web browser. Mosaic introduced a graphical user interface that let ordinary people navigate the World Wide Web without technical expertise, and it is credited as the first browser to achieve mainstream popularity. The ripple effect was enormous: Mosaic's accessibility helped ignite the internet boom of the 1990s, a period when the web expanded at an extraordinary pace. The lead developers of Mosaic went on to found the Netscape corporation, releasing Netscape Navigator in 1994. Navigator moved quickly to the top of the market.

  Microsoft entered the arena in 1995 with Internet Explorer, and a full browser war followed. Microsoft's strategy was straightforward and effective: it bundled Internet Explorer with the Windows operating system and offered it as freeware with no usage restrictions. By the early 2000s, Internet Explorer held over 95% of the browser market, a concentration of dominance rarely seen in any technology sector.

  Netscape's response, launched in 1998, was to open its codebase to the public and found what became the Mozilla Foundation. The project that emerged from that effort was Firefox, which Mozilla released in 2004. Firefox's market share climbed to 32% by 2010, the first serious challenge to Internet Explorer's grip.

• 4. Chrome, Safari, and the Modern Era

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  Apple released Safari in 2003, built on its own WebKit code. Safari secured a strong position on Apple's own devices, though it never gained significant ground on other platforms. Its current global share sits at around 16%, almost entirely tied to the Apple ecosystem.

  Google launched Chrome in 2008. Unlike its competitors, Chrome steadily chipped away at Internet Explorer's lead year by year, and by 2012 it had become the most popular browser in the world. It has held that position ever since, now commanding roughly 69% of global market share across all devices. The foundation of Chrome is Google's open-source Chromium project, and that same codebase underlies a cluster of other significant browsers, including Microsoft Edge, Samsung Internet, and Opera.

  Microsoft's own path through this period traces an arc of retreat and reinvention. In 2015, it replaced Internet Explorer with a new browser called Edge, later referred to as Edge Legacy, as part of the Windows 10 release. That version was itself replaced in 2020 by a rebuilt Edge based on Chromium, aligning Microsoft's browser with the same underlying engine that powers Chrome. The original Internet Explorer, once dominant beyond any competitor's reach, had effectively ceased to be a meaningful product.

  Starting in the mid-2020s, a new category began to take shape: browsers with integrated artificial intelligence capabilities. New entrants such as Perplexity Comet and ChatGPT Atlas arrived, while established browsers added their own AI features. Chrome incorporated the Gemini chatbot, and Edge added Copilot.

• 5. Privacy, Security, and DRM

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  Web browsers sit in an exposed position on the internet, and hackers treat them as persistent targets. Exploiting security holes in browsers can allow attackers to steal information or destroy files, so browser vendors regularly patch vulnerabilities and encourage users to keep their software current. Antivirus programs and awareness of scams are the other layers of defense most commonly recommended.

  Privacy is a related but distinct concern. Browsers store cookies received from websites, and while some of those cookies hold useful data like login credentials or site preferences, others are used to track user behavior over extended periods. Most browsers include a menu option for deleting cookies, and some take a more aggressive stance by actively blocking trackers and fingerprinting scripts by default. A 2020 study divided browsers into two clear tiers on privacy grounds: Brave, DuckDuckGo, and Firefox Focus outperformed Chrome, Firefox, and Safari, largely because the first group blocks fingerprinting, tracking scripts, and ads more thoroughly.

  A third tension involves access to commercial media. Streaming services including Netflix, Disney+, and Spotify control their content through Digital Rights Management software, and browsers need a Content Decryption Module to access it. As of 2020, the CDMs used by dominant browsers require providers to pay significant licensing fees. That cost makes it effectively impossible for most independent open-source browsers to offer access to DRM-restricted services, drawing a hard line between major browsers and smaller alternatives.

• 6. Who Uses What, and Where

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  As of February 2025, Chrome holds approximately 69% of global browser market share, Safari sits at 16%, and Edge claims around 5%. Firefox and Samsung Internet each hold roughly 2%, with Opera at a similar level. Brave, the most notable of the smaller players, holds around 1%. A long tail of browsers including Yandex, UC Browser, DuckDuckGo, and others each account for less than 1% individually.

  The device on which people browse has shifted significantly. Before late 2016, desktop computers generated the majority of web traffic. Mobile devices, primarily smartphones, have represented the majority of traffic since then. As of February 2025, mobile accounts for 62% of internet traffic, desktop for 36%, and tablets for 2%.

  Browsers run on an expanding range of hardware beyond phones and computers. Tablets, smartwatches, smart televisions, and gaming consoles all host browser software. At the far end of the usage spectrum sits the headless browser, a browser that processes web pages entirely without displaying a graphical interface, used primarily in automated testing and data collection rather than by human users directly. The estimated 5.4 billion people who had used a browser as of 2023 represent a figure that would have been unimaginable to Sir Tim Berners-Lee when he completed WorldWideWeb alone in 1990.