Internet Explorer (formerly Microsoft Internet Explorer and Windows Internet Explorer, commonly abbreviated IE or MSIE) is a series of graphical web browsers developed by Microsoft and included in the Microsoft Windows line of operating systems, starting in 1995. It was first released as part of the add-on package Plus! for Windows 95 that year. Later versions were available as free downloads, or in service packs, and included in the original equipment manufacturer (OEM) service releases of Windows 95 and later versions of Windows. The browser is discontinued, but still maintained.
Internet Explorer was once the most widely used web browser, attaining a peak of about 95% usage share by 2003. This came after Microsoft used bundling to win the first browser war against Netscape, which was the dominant browser in the 1990s. Its usage share has since declined with the launch of Firefox (2004) and Google Chrome (2008), and with the growing popularity of operating systems such as Android and iOS that do not support Internet Explorer.
Estimates for Internet Explorer‘s market share are about 1.7% across all platforms, or by StatCounter’s numbers ranked 8th. On traditional PCs (e.g. excluding mobile and Xbox), the only platform on which it has ever had significant share it is ranked 5th at 3.7%, with Microsoft Edge, its successor, ranking 4th with a 4.7% market share (and IE is also after Edge overall). Edge first overtook Internet Explorer in terms of market share in August 2019. IE and Edge combined rank third, after Firefox, previously being second after Chrome.
Microsoft spent over US$100 million per year on Internet Explorer in the late 1990s, with over 1,000 people involved in the project by 1999.
Versions of Internet Explorer for other operating systems have also been produced, including an Xbox 360 version called Internet Explorer for Xbox and for platforms Microsoft no longer supports: Internet Explorer for Mac and Internet Explorer for UNIX (Solaris and HP-UX), and an embedded OEM version called Pocket Internet Explorer, later rebranded Internet Explorer Mobile made for Windows CE, Windows Phone and previously, based on Internet Explorer 7 for Windows Phone 7.
On March 17, 2015, Microsoft announced that Microsoft Edge would replace Internet Explorer as the default browser on its Windows 10 devices (while support for older Windows has since been announced, as of 2019 Edge still has lower share than IE’s, that is in decline). This effectively makes Internet Explorer 11 the last release (however IE 8, 9, and 10 also receive security updates as of 2019). Internet Explorer, however, remains on Windows 10 and Windows Server 2019 primarily for enterprise purposes. Since January 12, 2016, only Internet Explorer 11 has official support for consumers; Internet Explorer 10 also has extended support to January 2020 on certain platforms. Support varies based on the operating system’s technical capabilities and its support life cycle.
The browser has been scrutinized throughout its development for use of third-party technology (such as the source code of Spyglass Mosaic, used without royalty in early versions) and security and privacy vulnerabilities, and the United States and the European Union have alleged that integration of Internet Explorer with Windows has been to the detriment of fair browser competition.