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What is Internet Explorer?

Internet Explorer (commonly abbreviated as IE) is a proprietary web browser developed by Microsoft and was introduced in August 1995 as part of the Microsoft Plus! package for Windows 95. It rapidly became the dominant web browser, reaching its peak market share of approximately 95% during the early 2000s. IE played a pivotal role in popularizing the internet and the World Wide Web, shaping the web browsing experience for over two decades.

Internet Explorer was originally built upon the Trident rendering engine (also known as MSHTML), a proprietary engine designed to interpret and render HTML, CSS, JavaScript, and other web technologies. Over time, IE incorporated numerous proprietary features and extensions, such as ActiveX controls, Browser Helper Objects (BHOs), and integration with Windows OS, which made it popular for corporate environments and legacy web applications.

Despite its long-standing presence, Internet Explorer’s market share declined significantly due to competition from browsers like Mozilla Firefox, Google Chrome, and Microsoft’s own Edge browser. Microsoft officially ended mainstream support for Internet Explorer 11 in many versions of Windows 10 in 2021, encouraging users and enterprises to transition to Edge.

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Major Use Cases of Internet Explorer

Internet Explorer served diverse use cases during its lifespan, which contributed to its widespread adoption:

2.1 General Web Browsing

At its core, IE was used by millions for everyday web browsing — accessing websites, email portals, news, social media, online banking, and multimedia content. It supported the core web technologies necessary for rendering most web pages of its time.

2.2 Enterprise Web Applications and Legacy Systems

Many businesses developed intranet sites, portals, and web applications tightly coupled with IE’s proprietary features, such as ActiveX, VBScript, and specific Document Object Model (DOM) implementations. These dependencies made IE indispensable for enterprise workflows, especially in sectors like finance, healthcare, and government.

2.3 Secure Web Access

Internet Explorer incorporated multiple security features aimed at protecting users from malware, phishing, and malicious content. Its security zones model segmented sites by trust levels, allowing administrators to impose granular security policies.

2.4 Web Development and Compatibility Testing

Web developers relied on IE to test and debug their websites, especially when optimizing for the large user base dependent on IE. Microsoft introduced developer tools (F12 Developer Tools) in IE8 to aid this process.

2.5 Integration with Windows Ecosystem

IE was tightly integrated with Windows, enabling features like Active Desktop, Outlook integration, Windows Update delivery, and launching web content from other Windows applications.

2.6 Browser Extensibility and Add-ons

Through Browser Helper Objects (BHOs) and later add-ons, IE allowed third parties to extend browser functionality, adding toolbars, download managers, and security features.

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How Internet Explorer Works Along with Its Architecture

Internet Explorer’s architecture is a layered, modular design optimized for rendering and interacting with complex web content while integrating with Windows’ security and network infrastructure.

3.1 Core Components Overview

Component	Description
User Interface (UI)	The chrome of the browser — menus, toolbars, tabs (introduced later), address bar, etc.
Trident (MSHTML) Engine	Rendering engine responsible for parsing HTML, CSS, SVG, and rendering pages.
JScript Engine	Microsoft’s implementation of JavaScript used to execute client-side scripts.
Networking Stack	Handles HTTP/HTTPS protocols, caching, proxy configurations, and DNS resolution.
Security Manager	Implements security zones, sandboxing, and content filtering.
Extension Manager	Handles Browser Helper Objects (BHOs) and ActiveX controls for plugin support.

3.2 Rendering Engine: Trident

Trident is the foundational component interpreting HTML, CSS, DOM, and script to render web content visually. Over the years, Trident was updated with better CSS support and JavaScript performance enhancements but was often criticized for inconsistent standards compliance, which led to developer frustration.

3.3 JavaScript Engine: JScript

JScript executes the dynamic client-side logic embedded in web pages. It features Just-In-Time (JIT) compilation to improve performance but lags behind modern engines like V8 or SpiderMonkey in speed and optimization.

3.4 Security Architecture

IE’s security model is based on the Security Zones paradigm, dividing websites into Internet, Local Intranet, Trusted Sites, and Restricted Sites, each with tailored permissions for scripting, ActiveX, and downloads. Protected Mode (introduced in IE7 on Windows Vista) sandboxes web processes to mitigate attacks.

3.5 Extension and Plugin System

IE extensions could leverage BHOs or ActiveX controls, which are COM-based components with deep OS integration. While powerful, these posed significant security risks and stability concerns, contributing to IE’s decline.

3.6 Networking and Protocol Support

IE supports HTTP/1.1, HTTPS, FTP, and more, managing cookies, caching, and proxy configuration through WinINet (Windows Internet API). IE also introduced support for HTTP compression and partial page caching.

3.7 Integration with Windows Shell

IE components are integrated into Windows Shell, enabling rendering web content within Windows Explorer, system notifications, and support for desktop gadgets.

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Basic Workflow of Internet Explorer

Here’s a detailed overview of how IE processes and displays web content:

4.1 Browser Startup

• Loads user profile, saved sessions, bookmarks, cookies, and security settings.
• Initializes UI elements, extension managers, and network connections.

4.2 User Enters URL or Opens a Link

• Input URL is parsed and validated.
• DNS lookup is performed to resolve domain names.
• Network requests are initiated using HTTP/HTTPS protocols.

4.3 Content Download and Parsing

• HTML content is streamed to Trident.
• HTML parser converts markup to DOM nodes.
• CSS parser applies styles and calculates layout.
• Scripts (JScript) are parsed and executed, possibly altering DOM.
• Images, scripts, and other resources are loaded asynchronously.

4.4 Rendering and Painting

• Trident calculates element sizes, positions, and paints pixels.
• Updates are progressively rendered to the screen.
• User interactions (scrolling, clicks) trigger reflows or repaints as necessary.

4.5 Event Handling and Scripting

• User inputs generate DOM events.
• JScript event handlers execute, potentially changing UI dynamically.

4.6 Security Checks and Filtering

• Content is checked against security zone policies.
• SmartScreen filters warn users about suspicious sites or downloads.

4.7 Session Management and Persistence

• History, cookies, cache, and session storage are updated.
• Tabs and windows respond to user commands for navigation and management.

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Step-by-Step Getting Started Guide for Internet Explorer

Step 1: Locate and Launch Internet Explorer

• IE comes preinstalled on Windows systems up to Windows 10.
• Access via Start Menu > Windows Accessories > Internet Explorer.
• Alternatively, type “Internet Explorer” in the search bar.

Step 2: Familiarize with the User Interface

• Address bar for URL entry.
• Back, Forward, Refresh buttons.
• Favorites (Bookmarks) pane.
• Tabs interface (IE7 and above).
• Settings menu (gear icon).

Step 3: Navigate to a Website

• Enter a URL or search query in the address bar.
• Press Enter to load the page.

Step 4: Use Tabs

• Open new tabs by clicking the new tab button or pressing Ctrl+T.
• Switch between tabs by clicking or using Ctrl+Tab.

Step 5: Manage Favorites

• Click the star icon to add or organize bookmarks.
• Access Favorites through the Favorites menu.

Step 6: Adjust Security and Privacy Settings

• Open Internet Options via the gear icon or Control Panel.
• Navigate to the Security tab to modify zone settings.
• Enable or disable ActiveX and scripting as necessary.
• Clear browsing data from the General tab.

Step 7: Use Developer Tools

• Press F12 to open Developer Tools.
• Inspect elements, debug scripts, view network traffic.

Step 8: Update Internet Explorer

• IE updates are delivered through Windows Update.
• Regularly check for system updates to maintain security.