Internet Explorer
Internet Explorer is a series of proprietary graphical web browsers developed by Microsoft Corporation, initially released on August 16, 1995, as part of the Microsoft Plus! add-on package for Windows 95.[1] The browser achieved widespread adoption through its tight integration with the Windows operating system, enabling seamless access for hundreds of millions of users and facilitating the mainstream expansion of the World Wide Web during the late 1990s and early 2000s.[1] This default bundling contributed to Internet Explorer attaining a global desktop market share exceeding 90% at its peak around 2002–2003, as measured by usage analytics.[2] However, the practice sparked significant antitrust litigation, culminating in the United States v. Microsoft Corp. case initiated in 1998, where a federal court ruled that Microsoft had unlawfully maintained its operating system monopoly by tying Internet Explorer to Windows to exclude competitors like Netscape Navigator.[3][4] Over time, Internet Explorer encountered mounting challenges, including persistent security vulnerabilities that exposed users to exploits and a reputation for lagging in support for evolving web standards, which hindered developer efforts and web innovation.[5] These issues, combined with the rise of open-source alternatives offering superior speed, privacy, and compatibility, eroded its market position; by the early 2010s, its share had plummeted below 50%.[6] Microsoft ultimately retired the Internet Explorer 11 desktop application on June 15, 2022, urging migration to its successor, Microsoft Edge, while retaining a compatibility mode for legacy enterprise needs until 2029.[7][8]History
Origins and Development (1995–1997)
Microsoft licensed the source code for Spyglass Mosaic, a commercial derivative of the NCSA Mosaic browser, in late 1994 for approximately $2 million upfront plus royalties on each distributed copy.[9] This agreement enabled Microsoft to develop its first web browser amid growing internet adoption, following Bill Gates' internal recognition of the web's strategic importance after initially underprioritizing it.[1] The codenamed "O'Hare" project resulted in Internet Explorer 1.0, released on August 16, 1995, as part of the Microsoft Plus! add-on pack for Windows 95.[10] This initial version supported basic HTML rendering, inline images, and limited HTTP functionality but lacked features like tables and was restricted to 512-color displays on Windows platforms.[11] Internet Explorer 1.5 followed in fall 1995 exclusively for Windows NT, introducing rudimentary HTML table support to address a key Mosaic limitation.[12] Building on the Spyglass base with minimal modifications, Internet Explorer 2.0 launched on November 22, 1995, for Windows 95 and NT 3.51/4.0, and April 1996 for Macintosh.[13] Enhancements included full table rendering, Java applet support via Microsoft Java Virtual Machine, and Progressive Networks' streaming audio/video plugins, alongside SSL encryption and 128-bit key support in a separate "Gold" edition.[14] These updates aimed to close gaps with Netscape Navigator, which held over 90% market share, though IE remained an optional download rather than a core Windows component.[15] By mid-1996, Microsoft accelerated development to compete more aggressively, releasing Internet Explorer 3.0 on August 13, 1996, for Windows (with Macintosh following January 8, 1997).[16] This version marked a shift from heavy reliance on Spyglass code, incorporating original Microsoft rendering improvements for partial CSS1 compliance, Dynamic HTML elements, and ActiveX controls for enhanced multimedia integration.[17] Offered free of charge—eschewing retail packaging to minimize Spyglass royalties—IE 3.0 bundled with Internet Mail and News clients, fostering ecosystem ties while drawing antitrust scrutiny for distribution tactics.[11] Adoption grew modestly, capturing under 10% market share by late 1997, as Microsoft invested in cross-platform ports and security features like enhanced certificate handling.[18]Browser Wars and Dominance (1998–2005)
The intensification of the browser wars in 1998 saw Microsoft leverage the release of Windows 98 on June 25, which tightly integrated Internet Explorer 4.0, introducing features like Active Desktop that blurred lines between the OS and browser to enhance user experience through seamless web content rendering on the desktop.[19] This bundling strategy, combined with free distribution to original equipment manufacturers (OEMs), accelerated IE's adoption amid competition from Netscape Navigator, which held a declining share after peaking at around 90% in 1995.[20] By September 28, 1998, market research indicated IE had overtaken Netscape as the leading browser, capturing over 50% usage share by year's end.[21] [22] The U.S. Department of Justice filed an antitrust lawsuit against Microsoft on May 18, 1998, alleging that the company unlawfully tied IE to Windows to exclude competitors like Netscape, thereby maintaining its operating system monopoly through exclusionary contracts with OEMs that restricted alternative browsers.[23] Microsoft countered that integration provided technical efficiencies, such as shared code for rendering and scripting, rather than mere anticompetitive tactics.[24] In November 1998, AOL acquired Netscape for $4.2 billion, but the deal failed to reverse Netscape's momentum loss, as its browser share continued eroding under IE's preinstalled ubiquity on Windows machines.[25] Internet Explorer 5.0, released on March 18, 1999, further solidified gains with improved standards support and features like HTML Components, achieving over 50% market share by early 2000 and pushing IE versions collectively above 80%.[26] The antitrust trial concluded in 2000 with a ruling that Microsoft violated Section 2 of the Sherman Act by willfully maintaining its monopoly, though appeals delayed remedies.[27] IE 6.0 launched on August 27, 2001, bundled with Windows XP (released October 25, 2001), emphasizing security enhancements and reaching approximately 95% market share within a year.[28] [29] A November 2001 settlement with the DOJ imposed behavioral restrictions, including allowing OEMs to customize desktop icons and promote rival software, but stopped short of unbundling IE or structural divestiture, permitting Microsoft to continue integrating the browser while sharing APIs with competitors.[30] Despite these constraints, IE's dominance endured through 2005, peaking at 95-96% usage share around 2002-2004, driven by Windows Update auto-deployments, network effects from web developers targeting IE-specific features, and user inertia on preinstalled software.[31] [32] This period marked IE's unchallenged hegemony, as alternative browsers like Netscape's successors struggled against the default positioning on over 90% of PCs.[33]Post-Antitrust Improvements (2006–2013)
In response to competitive pressures and the stagnation of Internet Explorer 6, Microsoft released Internet Explorer 7 on October 18, 2006, for Windows XP, introducing tabbed browsing, an integrated RSS feed reader, and a phishing filter to enhance security against online threats.[34][35][36] The update also featured a redesigned user interface with a Favorites Center for managing bookmarks and feeds, aiming to improve usability after years of minimal changes.[35] IE7 became the default browser in Windows Vista, reflecting Microsoft's efforts to align the product with evolving web standards and user expectations post-regulatory scrutiny.[37] Internet Explorer 8, launched on March 19, 2009, emphasized standards compliance by introducing a standards rendering mode that supported CSS 2.1 and early HTML5 elements, alongside developer tools for debugging.[38][39] New features included accelerators for quick actions like mapping or translation, and Web Slices for dynamic content updates without full page reloads, which sought to bridge proprietary extensions with broader web interoperability.[39] These enhancements addressed prior criticisms of non-compliance, enabling better cross-browser consistency while maintaining backward compatibility options.[38] Building on this, Internet Explorer 9, released on March 14, 2011, incorporated GPU hardware acceleration for rendering graphics and text, shifting processing from CPU to GPU to boost performance in web applications.[40][41] The version featured a faster JavaScript engine and improved adherence to web standards, including better support for SVG and WOFF fonts, which enhanced rendering speed and reduced compatibility issues.[41] Internet Explorer 10, integrated with Windows 8 upon its October 26, 2012 release and later ported to Windows 7 on February 26, 2013, advanced touch-optimized interactions with features like "Flip Ahead" for gesture-based navigation and pinning sites to the Start screen.[42][43] It enforced stricter HTML5 compliance by default, removing the compatibility view button in Metro mode to prioritize modern standards, while bolstering security through sandboxing and iframe isolation.[43] These updates positioned IE as more performant and ecosystem-integrated, responding to mobile and touch paradigms amid ongoing EU antitrust remedies requiring browser choice screens from 2011.[42]End of Mainstream Support and Removal (2014–2022)
In August 2014, Microsoft announced that it would end technical support and security updates for Internet Explorer versions 8, 9, and 10 on January 12, 2016, regardless of the host operating system's support status, shifting focus to Internet Explorer 11 as the sole supported version.[44] This policy change aligned browser support more closely with platform maturity, emphasizing IE11's role in delivering modern web standards without further major version releases.[45] On January 12, 2016, support for IE8, IE9, and IE10 officially ceased, leaving IE11 as the only actively maintained edition and prompting users of legacy versions to upgrade or face unpatched vulnerabilities.[46] IE11's mainstream support phase, which included non-security fixes and feature enhancements, concluded in October 2020, transitioning to extended support limited to security updates.[47] In May 2021, Microsoft declared that the Internet Explorer 11 desktop application would retire on June 15, 2022, for Windows 10 Semi-Annual Channel editions, with the browser redirecting users to Microsoft Edge featuring an IE compatibility mode to handle legacy sites.[48] This retirement marked the end of all direct support for the standalone IE11 application, as Microsoft prioritized Edge—initially rebuilt on the Chromium engine in January 2020—for improved performance, security, and cross-platform compatibility.[49] Following the June 15, 2022, cutoff, IE11 ceased receiving updates and functionality on consumer Windows 10 versions, with remaining installations uninstalled as an optional feature via Windows Settings or PowerShell commands likeDisable-WindowsOptionalFeature -Online -FeatureName "Internet-Explorer-Optional-amd64".[5] A Microsoft Edge update on February 14, 2023, permanently disabled any lingering IE11 instances on supported systems, removing icons and shortcuts while preserving IE mode in Edge for enterprise needs until at least 2029. Enterprise editions of Windows 10 retained extended OS support beyond this date, but IE11 itself was no longer viable outside compatibility emulation.[8]
Technical Architecture
Rendering Engine and Trident
Trident, also referred to as MSHTML, served as the proprietary rendering engine for Microsoft Internet Explorer from version 4.0 to 11. Introduced with Internet Explorer 4.0 in 1997, it marked Microsoft's shift from licensing the Spyglass Mosaic-derived engine used in earlier versions to developing its own layout component designed for integration into Windows applications.[50][51] This engine handled HTML parsing, CSS styling, and JavaScript execution, enabling features like Dynamic HTML (DHTML) for dynamic page manipulation.[52] Early iterations of Trident prioritized proprietary extensions over strict web standards compliance, resulting in rendering behaviors that diverged from specifications such as CSS1 and HTML 4.0. For instance, Internet Explorer 6, released in 2001 and reliant on Trident's foundational implementation, exhibited bugs like the "double margin" issue in floated elements and incomplete support for selectors, which necessitated workarounds in web development known as "IE-specific hacks."[53] These inconsistencies stemmed from Trident's design focus on backward compatibility with legacy Microsoft content rather than full adherence to emerging W3C standards, contributing to fragmentation in cross-browser rendering during the browser wars era.[54] Microsoft incrementally enhanced Trident's standards support in subsequent releases. Internet Explorer 7, launched in 2006, incorporated a rewritten layout core to better align with CSS 2.1, fixing over 500 rendering bugs and introducing alpha transparency for PNGs.[53] Further refinements in Internet Explorer 8 (2009) added support for CSS 2.1 selectors and the<!DOCTYPE> enforcement for standards mode, while Internet Explorer 9 (2011) enabled hardware-accelerated rendering via GPU and partial HTML5/CSS3 features, achieving a score of 95/100 on the Acid3 test—a benchmark for standards conformance.[54] Despite these advances, Trident lagged in full implementation of modern APIs compared to competitors like Gecko and WebKit, with Internet Explorer 11 (2013) still requiring compatibility modes for legacy sites.[55] The engine's final major iteration powered IE11's Trident 7.0, emphasizing performance optimizations but retaining quirks mode for enterprise compatibility.[56]
Integration with Windows Ecosystem
Internet Explorer was bundled as the default web browser with Windows operating systems beginning with version 2.0 included in Windows 95 OEM Service Release 1 (OSR1), released in August 1996, and Windows NT 4.0. Subsequent versions, such as Internet Explorer 4.0 released on September 23, 1997, were pre-installed on Windows 98 and later editions including Windows 2000, XP, Vista, and 7, achieving peak market penetration through this distribution model. This bundling positioned IE as the system's primary handler for web protocols like HTTP and HTTPS, directing URL invocations across applications to its rendering engine unless user-configured otherwise. A key aspect of integration emerged with Internet Explorer 4.0 via the Windows Desktop Update, which enabled shell-level features like Active Desktop—allowing HTML web content to be displayed as dynamic desktop backgrounds—and web view integration in Windows Explorer, where folder contents could render as HTML pages using IE's components. These enhancements relied on the Trident (MSHTML) rendering engine, which was embedded in the Windows shell for consistent web content display, extending beyond the browser to features like channel bars and subscribed web channels on the taskbar. The MSHTML engine was further shared with numerous Windows-native applications and components, including CHM-based Help files, Outlook Express for HTML email rendering, and utilities like the Address Book, ensuring uniform HTML/CSS/ActiveX support system-wide but also creating dependencies that complicated removal or replacement. Updates to IE were delivered through Windows Update starting prominently with Service Pack integrations in Windows XP (2001 onward), synchronizing browser security patches and features with OS maintenance to streamline ecosystem cohesion. This tight coupling, while boosting usability for web-integrated tasks, drew antitrust scrutiny in the late 1990s for hindering competition, as IE's protocols and shell hooks persisted even after attempted uninstallations in versions like Windows 98. Microsoft addressed partial decoupling in later releases, such as Windows 7 (2009), by permitting optional IE installation while retaining MSHTML for legacy compatibility.Extensibility and ActiveX
Internet Explorer achieved extensibility primarily through ActiveX controls, a Microsoft framework that enabled the embedding of reusable Component Object Model (COM)-based software components directly into web pages.[57] ActiveX technologies were formally announced by Microsoft on March 12, 1996, as an evolution of earlier OLE (Object Linking and Embedding) standards, with initial developer specifications available since January of that year.[58] Support for hosting ActiveX controls within HTML content was added in Internet Explorer 3.0, released on August 13, 1996, allowing web developers to insert interactive elements via the<OBJECT> tag.[57]
These controls facilitated advanced features such as dynamic forms, multimedia playback, and custom animations by leveraging native Windows APIs, offering performance advantages over cross-platform alternatives like Java applets, which relied on a virtual machine.[59] Developers could distribute signed ActiveX binaries, authenticated via Microsoft's Authenticode system, which prompted users for installation approval, though unsigned controls faced stricter restrictions in later IE versions.[60] This model supported "ActiveX Documents," enabling full applications—like word processors or spreadsheets—to render within the browser frame with their native toolbars and menus, enhancing integration with the Windows desktop environment.[61]
Beyond core ActiveX, Internet Explorer extended functionality through Browser Helper Objects (BHOs), COM interfaces registered in the Windows registry that injected code into browser processes for tasks like ad blocking or search enhancements, introduced around Internet Explorer 4.0 in 1997.[62] Toolbars, another extensibility vector, allowed third-party additions via COM automation, with examples including the Google Toolbar released in 2000, which hooked into IE's address bar and menus.[62] However, this deep system integration, where extensions ran in the browser's privileged context without sandboxing, exposed users to risks including arbitrary code execution if controls were malformed or malicious, contributing to IE's reputation for vulnerabilities in the late 1990s and early 2000s.[59] Microsoft gradually mitigated these through features like kill bits—registry entries disabling specific controls—and enhanced prompting in IE 6 (2001), but ActiveX remained Windows-centric and declined with the shift to standards-based web technologies.[57]