What is Microsoft Internet Explorer and why does it matter
Microsoft Internet Explorer (IE) was a web browser from Microsoft, first released in 1995 and retired in mid‑2022. It played a central role in the browser wars of the 1990s and 2000s, influencing web standards, enterprise practices, and security expectations. Today it is best understood as a historically significant but now obsolete product, replaced primarily by Microsoft Edge. This page explains what Internet Explorer was, how it worked, why it declined, and what you should know if you still encounter it.
Key facts at a glance
| Attribute | Verified Detail | Source Type |
|---|---|---|
| Initial release | August 1995 (with Windows 95) | Company release notes |
| Final version | IE 11 (for Windows 10/8.1/7) | Microsoft documentation |
| End of support | June 15, 2022 (for certain Microsoft 365 apps) | Microsoft lifecycle policy |
| Successor | Microsoft Edge (Chromium-based) | Microsoft product roadmap |
| Rendering engines | Trident (legacy), EdgeHTML (IE 11 on Windows 10), legacy IE mode uses Trident | Microsoft developer docs |
Origins and early history (1994–1999)
Internet Explorer began as a licensed version of Spyglass Mosaic. It shipped with Windows 95 in August 1995, positioning Microsoft in the emerging graphical web browser market. Early iterations focused on integrating browsing into Windows and supporting competing standards of the time. By the late 1990s, IE introduced features such as iframe elements, XMLHTTP (an early precursor to AJAX), and DHTML behaviors, which were influential but sometimes inconsistent with emerging web standards.
The browser wars and peak adoption (2000–2003)
With the rise of the web, IE became the dominant browser, helped by its inclusion with Windows and aggressive distribution practices. Internet Explorer 6, released in 2001, achieved very high global adoption but became synonymous with security vulnerabilities and non‑standard CSS and JavaScript behavior. This period laid the groundwork for later web standards movements and developer practices aimed at cross‑browser compatibility.
Technical architecture and how it worked
Internet Explorer’s architecture centered on the Trident rendering engine, which parsed HTML, applied CSS, and executed ECMAScript via JScript. Over time, Microsoft introduced features like DirectAnimation, filters, and proprietary CSS extensions to enable rich web experiences. However, these additions often diverged from W3C and WHATWG standards, leading to compatibility challenges for developers. Security features such as Protected Mode and low‑integrity zones were introduced to mitigate risks from active content, especially in later versions.
Key components and data points
| Component | Role | Notes |
|---|---|---|
| Trident (MSHTML) | Layout and rendering | Used through IE 11; legacy in IE mode |
| JScript engine | Client‑side scripting | ECMAScript implementation, updates through IE 11 |
| IE Enhanced Security Configuration | Reduced attack surface on servers | Common in Windows Server deployments |
| Compatibility View | Emulated older rendering behavior | Helped sites built for older IE versions |
Decline, security challenges, and standards impact
By the early 2010s, Internet Explorer’s market share declined as competitors introduced faster JavaScript engines, better standards support, and more secure defaults. IE became a symbol of outdated web practices, largely due to its non‑standard implementations and the difficulty of testing for IE‑specific bugs. Microsoft responded with improved security mitigations, cumulative updates, and eventually a shift in strategy toward a modern browser built on Chromium, culminating in the release of Microsoft Edge. IE’s legacy includes accelerating the need for rigorous standards compliance and robust cross‑browser testing.
Notable missteps and vulnerabilities
- Slow security update cycles compared with emerging browser vendors.
- Proprietary features like ActiveX, which introduced significant security risks.
- Inconsistent CSS and ECMAScript support, complicating web development.
- Deprecated protocols and weak defaults in earlier versions (e.g., MD5, SHA1).
Deprecation and end of life
Microsoft retired Internet Explorer in phases. On June 15, 2022, IE stopped working in certain Microsoft 365 apps. On June 9, 2023, the browser was removed from Windows as a component, although older Windows versions may retain limited access via Internet Explorer mode in Edge for legacy line‑of‑business applications. For most users, IE is no longer the default or recommended way to browse the web; Edge provides updated security, performance, and compatibility.
Practical guidance if you still use or encounter IE
If you encounter sites that require Internet Explorer, use Edge’s IE mode rather than installing or re‑enabling the legacy browser. IE mode allows those sites to function while giving you the security and performance of a modern browser. Organizations managing legacy apps should plan migrations and test with modern alternatives, because continued reliance on IE increases risk and operational overhead.
Summary and lasting significance
Microsoft Internet Explorer was a foundational browser that shaped the early web but is now retired in favor of modern, standards‑compliant alternatives. Understanding IE helps make sense of web history, security practices, and the evolution of browser standards. Its replacement, Microsoft Edge, inherits a Chromium foundation while supporting legacy needs through IE mode. For most users and enterprises, moving away from IE entirely remains the strongest path for security, compatibility, and long‑term maintainability.