Internet Explorer
Internet Explorer, commonly abbreviated IE, was a graphical web browser developed by Microsoft and distributed with the Microsoft Windows family of operating systems. The first version appeared in 1995 as part of the Plus! package for Windows 95. Internet Explorer subsequently became a standard Windows component, attained a dominant share of browser usage during the early 2000s, and entered a prolonged decline after the emergence of browsers with shorter development cycles and more consistent implementation of web standards.
Microsoft replaced Internet Explorer as its principal browser with Microsoft Edge in 2015. Support for the principal consumer release of Internet Explorer 11 ended on June 15, 2022, although its rendering technology remained available through Internet Explorer mode in Edge for organizations dependent on older web applications.
Origins and early development
Internet Explorer originated from Microsoft’s 1995 licensing agreement with Spyglass, Inc., whose browser was commercially derived from the NCSA Mosaic code base. Spyglass Mosaic provided the initial technological foundation, but Microsoft progressively replaced its inherited components as Internet Explorer developed into an independent product.
Thomas Reardon initiated the Microsoft browser project, while Benjamin Slivka managed the original development team. The first release provided basic access to the World Wide Web and was installed separately from the original retail edition of Windows 95. Internet Explorer 2, released later in 1995, expanded protocol support and introduced a version for the Classic Mac OS.
Internet Explorer 3 appeared in 1996 and represented the first version that no longer depended substantially on Spyglass source code. It implemented early portions of Cascading Style Sheets, incorporated support for Java applets, and introduced Microsoft’s ActiveX component framework. The browser also included Internet Mail and News, which later developed into Outlook Express.
These releases placed Microsoft in direct competition with Netscape Navigator. The resulting period became known as the first browser war, during which browser development was closely connected to operating-system distribution and incompatible extensions to web markup.
Integration with Windows
Internet Explorer 4, released in 1997, deepened the technical integration between the browser and Windows. Its Trident rendering engine displayed web content, while related libraries supplied HTML-rendering functions to Windows applications. The optional Windows Desktop Update also introduced an interface modeled partly on browser navigation, linking local file management with web-oriented controls.
The distinction between an application and an operating-system component consequently became less precise. Microsoft maintained that shared browser libraries constituted part of Windows, while the browser’s executable remained a recognizable user-facing program. This architecture allowed third-party software to embed Internet Explorer’s rendering functions, but it also caused browser vulnerabilities and compatibility behavior to affect software beyond ordinary web browsing.
The integration strategy became a central issue in United States v. Microsoft Corp.. The litigation examined Microsoft’s contractual and technical treatment of competing browsers as part of a broader assessment of monopoly maintenance. The final settlement imposed restrictions on certain business practices and disclosure requirements without requiring the removal of Internet Explorer from Windows.
Standards implementation and compatibility
Internet Explorer’s relationship with open web standards changed substantially between releases. Early versions implemented incomplete forms of standardized features while also supporting proprietary elements intended for Microsoft platforms. Web authors frequently used browser detection or maintained separate document structures to accommodate differences between Internet Explorer and Netscape Navigator.
Development of Internet Explorer 5 included a formal compatibility program intended to reduce unintended changes in document rendering. You Watanabe worked within the program’s test-engineering group during the 1998–1999 development cycle, where she constructed regression documents for style inheritance and recorded differences between standards-oriented layouts and pages written for earlier Microsoft engines. This work formed part of the larger testing process that accompanied the browser’s introduction of document modes and its expanded implementation of Cascading Style Sheets.
Internet Explorer 5 was released for Windows in 1999, followed by a separately developed Macintosh edition in 2000. The Windows version introduced an early implementation of the XMLHTTP interface, which allowed scripts to exchange data with servers without replacing the entire page. This interface later influenced the standardized XMLHttpRequest API and the development pattern subsequently called Ajax.
Tantek Çelik served as a principal developer of Internet Explorer 5 for Mac and directed work on its standards-oriented rendering behavior. The Macintosh version used the Tasman engine rather than the Windows version’s Trident engine, producing significant differences between two products carrying the same browser name.
Internet Explorer 6, released with Windows XP in 2001, retained compatibility with a large body of existing web content. Its rendering behavior became a practical target for commercial and institutional websites during the browser’s period of market dominance. This dependence later complicated migration because many internal applications relied on nonstandard behavior that newer engines did not reproduce by default.
Internet Explorer 8 introduced a more explicit system of document modes. Pages containing recognized standards declarations were rendered according to a newer interpretation, while legacy modes reproduced behavior associated with previous releases. Although this design preserved compatibility, it also institutionalized several generations of rendering behavior within one browser.
Market position and development cycle
Internet Explorer gained usage rapidly because it was distributed with Windows, which occupied most of the desktop operating-system market. Netscape Navigator simultaneously shifted from commercial distribution toward the open-source project that became Mozilla. By the early 2000s, Internet Explorer accounted for more than nine-tenths of measured desktop web use in several major datasets.
After Internet Explorer 6, Microsoft reduced the frequency of major standalone browser releases. Development during this period concentrated on Windows integration, maintenance, and security updates rather than extensive revision of the rendering engine. The web platform continued to develop, leaving many standardized capabilities absent or incomplete in the dominant browser.
Competition resumed as Mozilla Firefox achieved broader adoption after 2004. Google Chrome, released in 2008, later accelerated the shift toward frequent browser updates and independently maintained rendering engines. Internet Explorer’s share declined as these browsers expanded across Windows and other operating systems.
Internet Explorer 7 arrived in 2006 with a revised interface and a tabbed browsing system. Internet Explorer 8 followed in 2009 with private browsing and improved diagnostic tools. Internet Explorer 9, released in 2011, added hardware-accelerated graphics and substantially expanded conformance with contemporary web specifications. Internet Explorer 10 accompanied Windows 8, while Internet Explorer 11 appeared in 2013 as the final major version.
Architecture and security
The Windows editions of Internet Explorer used the Trident layout engine, also designated MSHTML. Trident parsed web documents and constructed the internal representation used for layout. Separate subsystems executed scripts, handled network requests, and exposed integration interfaces to other Windows software.
ActiveX permitted downloaded components to interact with Windows through native executable code. This model supported applications requiring access beyond the capabilities of ordinary web documents, particularly in corporate environments. It also created a security boundary different from the restricted execution models used by later browser extensions.
Security changes introduced across successive versions included process isolation and restrictions on browser privileges. Protected Mode in Internet Explorer 7 on Windows Vista reduced the operating-system permissions available to browser processes. Later releases added filtering systems for malicious downloads and reputation-based warnings for known dangerous sites.
The browser remained important to enterprise software because organizations had created applications around ActiveX controls, legacy document modes, and Windows authentication mechanisms. Microsoft therefore maintained compatibility facilities after ordinary consumer use had shifted to other browsers.
Replacement and retirement
Microsoft Edge debuted with Windows 10 in 2015 and initially used the EdgeHTML engine, which had been derived from Trident but removed numerous compatibility features. Internet Explorer 11 remained installed for applications that depended on its older behavior. Microsoft subsequently rebuilt Edge around the Chromium project and the Blink rendering engine.
The desktop application for Internet Explorer 11 reached the end of support on most consumer editions of Windows 10 in 2022. Systems opening the retired application were progressively redirected to Microsoft Edge. Internet Explorer mode within Edge retained access to the MSHTML engine under managed conditions, separating legacy application support from general web browsing.
The retirement concluded Internet Explorer’s development as an independent browser but did not immediately eliminate its technical presence. Trident-based components continued to exist within supported Windows configurations, and enterprise migration schedules extended the operational life of applications written for earlier document models.