Windows Internet Explorer (formerly Microsoft Internet Explorer abbreviated MSIE), commonly abbreviated to IE, is a series of graphical web browsers developed by Microsoft and included as part of the Microsoft Windows line of operating systems starting in 1995. It has been the most widely used web browser since 1999, attaining a peak of about 95% usage share during 2002 and 2003 with IE5 and IE6 but steadily declining since, despite the introduction of IE7. Microsoft spent over 100 million dollars (USD) a year in the late 1990s, with over 1000 people working on IE by 1999.
Internet Explorer was first released as part of the add-on package Plus! for Windows 95 in 1995. Later versions were available as free downloads, or in service packs, and included in the OEM service releases of Windows 95 and later versions of Windows. The most recent release is version 7.0, which is available as a free update for Windows XP Service Pack 2, and Windows Server 2003 with Service Pack 1 or later, Windows Vista, and Windows Server 2008. Internet Explorer 8 is under development and is expected to be released by the end of 2008.
Other versions available since the late 1990s include an embedded OEM version called Internet Explorer for Windows CE (IE CE) available for WinCE based platforms and is currently based on IE6. Internet Explorer for Pocket PC, later rebranded Internet Explorer Mobile for Windows Mobile was also developed, and remain in development alongside the more advanced desktop versions.
The Internet Explorer project was started in the summer of 1994 by Thomas Reardon and subsequently led by Benjamin Slivka, leveraging source code from Spyglass, Inc. Mosaic, an early commercial web browser with formal ties to the pioneering NCSA Mosaic browser. In late 1994, Microsoft licensed Spyglass Mosaic for a quarterly fee plus a percentage of Microsoft's non-Windows revenues for the software. Although bearing a name similar to NCSA Mosaic, Spyglass Mosaic had used the NCSA Mosaic source code sparingly.
Internet Explorer for Mac and Internet Explorer for UNIX (the latter for use through the X Window System on Solaris and HP-UX), and versions for many older versions of Windows have been discontinued, and are no longer available from Microsoft. Only selected supported Windows, and Windows Mobile versions remain in active development.
Internet Explorer 1.0 debuted in August 1995. It was a reworked version of Spyglass Mosaic which Microsoft had licensed, like many other companies initiating browser development, from Spyglass Inc. It came with Microsoft Plus! for Windows 95 and OEM release of Windows 95. It was installed as part of the Internet Jumpstart Kit in Plus!. The Internet Explorer team began with about half a dozen people in early development. Internet Explorer 1.5 was released several months later for Windows NT and added support for basic table rendering. However, by including it for free on their OS they did not have to pay royalties to Spyglass Inc., which resulted in a lawsuit and multi-million USD settlement.
Internet Explorer 3.0, was released in August 1996, and went on to be much more popular than its predecessors. It was developed without Spyglass source code, although still crediting Spyglass "technology" in the program's documentation. Internet Explorer 3 was the first major browser with CSS support, although this support was only partial. Released on August 13, 1996, it also introduced support for ActiveX controls, Java applets, inline multimedia, and the PICS system for content metadata. Version 3 also came bundled with Internet Mail and News, NetMeeting, and an early version of the Windows Address Book, and was itself included with Windows 95 OSR 2. Version 3 proved to be the first more popular version of Internet Explorer, which brought with it increased scrutiny. In the months following its release, a number of security and privacy vulnerabilities were found by researchers and hackers. This version of Internet Explorer was the first to have the 'blue e' logo. The Internet Explorer team consisted of roughly 100 people during the development of three months. The first major IE security hole, the Princeton Word Macro Virus Loophole, was discovered on August 22, 1996 in IE3. Backwards compatibility was handled by allowing Users who upgraded to IE3 to still use the last IE, because the installation converted the previous version to separate directory.
Internet Explorer 4.5 dropped support for 68k Macs, but offered new features such as easier 128-bit encryption.
Internet Explorer 5.0, launched on March 18, 1999, and subsequently included with Windows 98 Second Edition and bundled with Office 2000, was another significant release that supported bi-directional text, ruby characters, XML, XSLT and the ability to save web pages in MHTML format. IE5 was bundled with Outlook Express 5. Also, with the release of Internet Explorer 5.0, Microsoft released the first version of XMLHttpRequest, giving birth to Ajax (even though the term "Ajax" wasn't coined until years later.) It was the last with a 16-bit version. Internet Explorer 5.01, a bug fix version, was released in December 1999. Windows 2000 includes this version. Internet Explorer 5.5 followed in July 2000, improving its print preview capabilities, CSS and HTML standards support, and developer APIs; this version was bundled with Windows Me. Version 5.5 also included support for 128-bit encryption. However, Version 5 was the last version for Mac and UNIX. Version 5.5 was the last to have Compatibility Mode, which allowed Internet Explorer 4 to be run side by side with the 5.x. The IE team consisted of over 1000 people by 1999, with funding on the order of 100 million USD per year.
|Market Share for February, 2005|
|IE4 - .07%|
|IE5 - 6.17%|
|IE6 - 82.79%|
Internet Explorer 6.0 was released on August 27, 2001, a few months before Windows XP. This version included DHTML enhancements, content restricted inline frames, and partial support of CSS level 1, DOM level 1 and SMIL 2.0. The MSXML engine was also updated to version 3.0. Other new features included a new version of the Internet Explorer Administration Kit (IEAK), Media bar, Windows Messenger integration, fault collection, automatic image resizing, P3P, and a new look-and-feel that was in line with the "Luna" visual style of Windows XP, when used in Windows XP.
Internet Explorer 6.0 SP1 offered several security enhancements and coincided with XP SP1 patch release. In 2002, the [(protocol)|Gopher protocol] was disabled and support for it was dropped in Internet Explorer 7.
Internet Explorer 6.0 SV1 ('6 SP2') came out August 6, 2004 for Windows XP SP2 and offered various security enhancements and new color buttons on the user interface. IE6 updated the original 'blue e' logo to a lighter blue and more 3-d look.
The original release of Internet Explorer 7 required the computer to pass a Windows Genuine Advantage validation check prior to installing, but on October 5, 2007, Microsoft removed this requirement. As some statistics show, by mid-2008, Internet Explorer 7 exceeded Internet Explorer 6 in number of users.
Internet Explorer 8 is the latest version of Internet Explorer and has been in development since August 2007 at the latest. On March 5, 2008, the first public beta (Beta 1) was released to the general public. On August 27, 2008, the second public beta (Beta 2) was released. It supports Windows XP SP2 and SP3, Windows Server 2003 SP2, Windows Vista and Windows Server 2008 on both 32-bit as well as 64-bit architectures.
Security, ease of use, and improvements in RSS, CSS, and Ajax support are Microsoft's priorities for IE8. It includes much stricter compliance with web standards, including a planned full Cascading Style Sheets 2.1 compliance for the release version. All these changes allow Internet Explorer 8 to pass the Acid2 test. However, to prevent compatibility issues, IE8 also includes the IE7 rendering behavior. Sites that expect IE7 quirks can disable IE8's breaking changes by including a meta element.
Internet Explorer uses DOCTYPE sniffing to choose between "quirks mode" (renders similarly to older versions of MSIE) and standards mode (renders closer to W3C's specifications) for HTML and CSS rendering on screen (Internet Explorer always uses standards mode for printing). It also provides its own dialect of ECMAScript called JScript.
It fully supports XSLT 1.0 as well as an obsolete Microsoft dialect of XSLT often referred to as WD-xsl, which was loosely based on the December 1998 W3C Working Draft of XSL. Support for XSLT 2.0 lies in the future: semi-official Microsoft bloggers have indicated that development is underway, but no dates have been announced.
Internet Explorer has introduced a number of extensions to JScript which have been adopted by other browsers. These include the innerHTML property, which returns the HTML string within an element; the XMLHttpRequest object, which allows the sending of HTTP request and receiving of HTTP response; and the designMode attribute of the contentDocument object, which enables rich text editing of HTML documents. Some of these functionalities were not possible until the introduction of the W3C DOM methods. Its Ruby character extension to HTML is also accepted as a module in W3C XHTML 1.1, though it is not found in all versions of W3C HTML.
Microsoft submitted several other features of IE for consideration by the W3C for standardization. These include the 'behavior' CSS property, which connects the HTML elements with JScript behaviors (known as HTML Components, HTC); HTML+TIME profile, which adds timing and media synchronization support to HTML documents (similar to the W3C XHTML+SMIL); and the VML vector graphics file format. However, all were rejected, at least in their original forms. VML was, however, subsequently combined with PGML (proposed by Adobe and Sun), resulting in the W3C-approved SVG format, currently one of the few vector image formats being used on the web.
Other proprietary standards include, support for vertical text, but in a syntax different from W3C CSS3 candidate recommendation. Support for a variety of image effects and page transitions, which are not found in W3C CSS. Support for obfuscated script code, in particular
JScript.Encode(). Support for embedding EOT fonts in web pages.
Internet Explorer makes use of the accessibility framework provided in Windows. Internet Explorer is also a user interface for FTP, with operations similar to that of Windows Explorer (although this feature requires a shell window to be opened in recent versions of the browser, rather than natively within the browser). Visual Basic for Applications (VBA) is not supported, but available via extension (iMacros). Recent versions feature pop-up blocking and tabbed browsing. Tabbed browsing can also be added to older versions by installing Microsoft's MSN Search Toolbar or Yahoo's Yahoo Toolbar.
Prior to IE7, clearing the cache used to clear the index but the files themselves were not removed. This feature can be a potential security risk for both individuals and companies. From IE7, both the index entries and the files themselves are removed when the cache is cleared.
Internet Explorer uses a componentized architecture built around the Component Object Model (COM) technology. It is made up of five major components, each of which is contained in a separate
.dll and exposes a set of COM interfaces that enables it to be hosted by the Internet Explorer main executable,
iexplore.exe:WinInet.dll: WinInet.dll is the protocol handler for  and . It handles all network communication over these protocols.URLMon.dll: URLMon.dll is responsible for MIME-type handling and download of web content.MSHTML.dll: MSHTML.dll houses the Trident rendering engine introduced in Internet Explorer 4, which is responsible for displaying the pages on-screen and handling the Document Object Model of the web pages. MSHTML.dll parses the HTML/CSS file and creates the internal DOM tree representation of it. It also exposes a set of APIs for runtime inspection and modification of the DOM tree. The DOM tree is further processed by a layout engine which then renders the internal representation on screen.
Internet Explorer 8 introduces some major architectural changes, called Loosely Coupled IE (LCIE). LCIE separates the UI processes from the process hosting the different web applications in different tabs (tab processes). A UI process can create multiple tab processes, each of which can be of a different integrity level; each tab process can host multiple web sites. Each tab process has its own cookie cache. The two processes use asynchronous Inter-Process Communication to synchronize themselves. Generally, there will be a single tab process for all web sites. In Windows Vista with protected mode turned on, however, opening privileged content (such as local HTML pages) will create a new tab process as it will not be constrained by protected mode of operation.
Interner Explorer add-on components run with the same privileges as the browser itself, unlike client-side scripts that have a very limited set of privileges. Add-ons can be installed either locally, or directly by a web site. Since the add-ons have a more privileged access to the system, malicious add-ons can and have been used to compromise the security of the system. Internet Explorer 6 Service Pack 2 onwards provide various safeguards against this, including an Add-on Manager for controlling ActiveX controls and Browser Helper Objects and a "No Add-Ons" mode of operation as well as greater restrictions on sites installing add-ons.
Internet Explorer itself can be hosted by other applications via a set of COM interfaces. This can be used to embed the browser functionality inside the application. Also, the hosting application can choose to host only the MSHTML.dll rendering engine, rather than the entire browser.
Internet Explorer 6 SP2 onwards uses the Attachment Execution Service of Microsoft Windows to mark executable files downloaded from the Internet as being potentially unsafe. Accessing files marked as such will prompt the user to make an explicit trust decision to execute the file, as executables originating from the Internet can be potentially unsafe. This helps in preventing accidental installation of malware.
Internet Explorer 7 introduced the phishing filter, that restricts access to phishing sites unless the user overrides the decision. With version 8, it also blocks access to sites known to host malware. Downloads are also checked to see if they are known to be malware-infected.
In Windows Vista, Internet Explorer by default runs in what is called Protected Mode, where the privileges of the browser itself is severely restricted - it cannot make any system-wide changes. One can optionally turn this mode off but this is not recommended. This also effectively restricts the privileges of any add-ons. As a result, even if the browser or any add-on is compromised, the damage the security breach can cause is limited.
Patches and updates to the browser are released periodically and made available through the Windows Update service, as well as through Automatic Updates. Although security patches continue to be released for a range of platforms, most recent feature additions and security improvements are released for Windows XP only.
A number of security flaws affecting IE originated not in the browser itself, but ActiveX-based add-ons used by it. Because the add-ons have the same privilege as IE, the flaws can be as critical as browser flaws. This has led to the ActiveX-based architecture being criticized for being fault-prone. More recently, other experts have maintained that the dangers of ActiveX have been overstated and there are safeguards in place. Other browsers that use NPAPI as their extensibility mechanism are suffering the same problems. In an April 2005 eWeek opinions column, Larry Seltzer stated:
While there has been a striking lack of actual evidence that ActiveX is unsafe, there has been no shortage of baseless assertions and cheap shots against it. My favorite was the "Internet Exploder" incident in which Sun actually paid someone to write a malicious ActiveX control. The test system brought up all the warning dialogs about the program that you usually get and the Sun employee actually had the nerve to keep whacking on the enter key quickly so they would close as quickly as possible and didn't mention that there were any such warnings. Meanwhile, they also didn't mention that a signed Java applet could also perform dangerous privileged operations and would provide similar warnings. Most ActiveX criticism is simply uninformed, but this example was hypocritical and dishonest.
While Internet Explorer is not alone in having exploitable vulnerabilities, its ubiquity has resulted in many more affected computers when vulnerabilities are found. Microsoft has not responded as quickly as competitors in fixing security holes and making patches available, in some cases giving malicious web site operators months to exploit them before Microsoft releases a patch.
The adoption rate of Internet Explorer seems to be closely related to that of Microsoft Windows, as it is the default web browser that comes with Windows. Since the integration of Internet Explorer 2.0 with Windows 95 OSR 1 in 1996, and especially after version 4.0's release, the adoption was greatly accelerated: from below 20% in 1996 to about 40% in 1998 and over 80% in 2000. This effect, however, has recently been dubbed the "Microsoft monoculture", by analogy to the problems associated with lack of biodiversity in an ecosystem.
A CNN article noted at the release of Internet Explorer 4,'' "Microsoft's Internet Explorer has made inroads and various estimates put its share of the browser market 30 to 35 percent from about 10 percent a year ago.By 2002, Internet Explorer had almost completely superseded its main rival Netscape and dominated the market with up to 95 percent market share.
After having fought and won the browser wars of the late 1990s, Internet Explorer gained almost total dominance of the browser market. Having attained a peak of about 95% during 2002 and 2003, its market share has since declined at a slow but steady pace. This is mainly due to the adoption of Mozilla Firefox, which statistics indicate is currently the most significant competition. Nevertheless, Internet Explorer remains the dominant web browser, with a global usage share of around 75% (though measurements vary). Usage is higher in Asia and lower in Europe.
Firefox 1.0 had surpassed Internet Explorer 5 in early 2005 with Firefox 1.0 at roughly 8 percent market share. An article notes at the release of Internet Explorer 7 in October 2006, "IE6 had the lion's share of the browser market with 77.22%. Internet Explorer 7 had climbed to 3.18%, while Firefox 2.0 was at 0.69%."
Internet Explorer 7 was released at the same time as Firefox 2.0, and overtook Firefox 1.x by November 2006, at roughly 9% market share. Firefox 2.0 had overtaken 1.x by January 2007, , but IE7 did not surpass IE6 until December 2007. By January 2008, their respective version market share stood at 43% IE7, 32% IE6, 16% FF2, 4%SF 3, and both FF1.x and IE5 versions at less than half a percent.
The release of IE7 at the end of 2006 resulted in a collapse of IE6 market share; by February 2007 market version share statistics showed IE6 at about 50% and IE7 at 29%. Regardless of the actual market share, the most compatible version (across operating systems) of IE was 5.x, which had Mac OS 9 and Mac OS X, Unix, and most Windows versions available and supported for a short period in the late 1990s (although 4.x had a more unified codebase across versions) By 2007, IE had much narrower OS support, with the latest versions supporting only Windows XP Service Pack 2 and above.
|Years||Layout engine||Microsoft Windows||IBM OS/2||Apple Inc. Macintosh||Unix (HP-UX, Solaris)|
|Vista, WS 08||WS 03||XP||Me||2000||98||NT 4.0||95||3.1/NT 3.x|| X |
| 9 |
| 8 |
| 7 |
|IE 8||2008-||Trident VI||(with SP2)||(with SP2/SP3)|
|IE 7||2006-||Trident V||(with SP1/SP2)||(with SP2/SP3****)|
|IE 6||2001||Trident IV|| |
|IE 5.5||2000||Trident III||***|
|IE 5.0||1999|| Trident II (Win) |
|rowspan=\\"2\\"||rowspan=\\"2\\"||rowspan=\\"2\\" ***||rowspan=\\"2\\"|| |
| colspan=\\"2\\" |
|IE 3.0||1996||-||***||***||**||Win 3.1 version|
See also Internet Explorer Mobile. Non-desktop versions of IE have supported Windows CE also.
Microsoft has discontinued standalone installers for Internet Explorer to the general public. However, there are unofficial procedures for downloading the complete install package. Internet Explorer standalone hacks exploit a known workaround to DLL hell, which was introduced in Windows 2000, called DLL redirection
It is also possible to install Internet Explorer via Wine.
After Internet Explorer 7 is installed, an Internet Explorer 6 executable is still available in C:WINDOWSie7, hidden by default. Launching this executable provides the user with the older IE6 interface, however web pages are rendered using the IE7 engine. The IE6 engine can be re-enabled by placing a file named \\"iexplore.exe.local\\" into the IE7 folder.
As an alternative to using IE standalone, Microsoft now makes available Microsoft Virtual PC images containing pre-activated copies of Windows XP with either IE 6 or IE 7 installed. Microsoft recommends this approach for web developers seeking to test their pages in the different versions of IE as the standalone versions are unsupported and may not work the same way as a properly installed copy of IE.
While a major upgrade of Internet Explorer can be uninstalled in a traditional way if the user has saved the original application files for uninstallation, the matter of uninstalling the version of the browser that has shipped with an operating system remains a controversial one.
The idea of removing a stock install of Internet Explorer from a Windows system was proposed during the United States v. Microsoft case. Critics felt that users should have the right to uninstall Internet Explorer freely just like any other application software. One of Microsoft's arguments during the trial was that removing Internet Explorer from Windows may result in system instability.
The Australian computer scientist Shane Brooks demonstrated that Windows 98 could in fact run with Internet Explorer removed. Brooks went on to develop software designed to customize Windows versions by removing "undesired components", which is known as 98lite. He later created XPLite to support NT based operating systems. Both of these pieces of software can remove IE after the installation of the operating system.
There are methods for removing IE from a copy of the Windows install disc so it never touches the user's hard drive. A method developed by Fred Vorck involves the manual removal of IE from installation discs. His process has been automated as a feature of HFSLIP. nLite and HFSLIP are automated programs that allow users to exclude IE and many other Windows components from installation as desired. In some older versions of Windows and in Windows Fundamentals there is an option to install Internet Explorer.
Removing Internet Explorer does have a number of consequences. Some applications that depend on libraries installed by IE may fail to function, or have unexpected behaviors. Intuit's Quicken is a typical example, which depends heavily upon the HTML rendering components installed by the browser. The Windows help and support system will also not function due to the heavy reliance on HTML help files and components of IE. In versions of Windows before Vista, it is also not possible to run Microsoft's Windows Update or Microsoft Update with any other browser due to the service's implementation of an ActiveX control, which no other browser supports. In Windows Vista, Windows Update is implemented as a Control Panel applet.