Internet Explorer is a retired series of graphical web browsers developed by Microsoft that were used in the Windows line of operating systems. While IE has been discontinued on most Windows editions, it remains supported on certain editions of Windows, such as Windows 10 LTSB/LTSC. 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. 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. In 2015, Microsoft Edge was released to succeed Internet Explorer 11 as Microsoft's primary web browser. New feature development for Internet Explorer was discontinued the following year, and support for the browser officially ended on June 15, 2022, for Windows 10 Semi-Annual Channel (SAC) editions.