File Explorer

File Explorer is the application responsible for the Windows user interface and the default Windows file manager. The first build to include it was Windows 95 build 58s, under the name of Cabinet for the shell portion and File Cabinet for the file manager part. Build 189 is the first leaked build to rename Cabinet to Windows Explorer. During the development of Windows 95, several Shell Technology Previews were released for Windows NT 3.51, that brought the new user interface to the NT series. Internet Explorer 4 updated Windows Explorer with a new, web-integrated experience. Windows Vista saw major changes to Explorer, simplifying the UI somewhat, as well as removing features Microsoft thought were under-utilized. Windows 7 added Libraries to the Explorer experience. In Windows 8, Windows Explorer was renamed to File Explorer.

Development
File Explorer was first introduced during Windows 95 development, but it did not start out looking like its final design. In early builds, Explorer was named Cabinet, the Taskbar acted as a folder, and the Start Menu was not present. It was instead divided into three separate menus, each providing a portion of the final functionality. The first menu (denoted by the Windows logo) acted as a system menu where you could access applications using the 'Run' dialog, manipulate windows and shutdown Windows. The second menu (denoted by a magnifying glass) provided Windows Search-like functionality. The last menu was the 'Help' menu where you could access the Windows documentation and get basic system information.

Windows 95/NT 4.0
The Explorer design included in Windows 95 used large icons for folders and drives, and used a menu bar at the top, which contained options such as renaming and deleting files. By default, new folders or directories would open a new Explorer window, but this design could be configured to use a single window with a toolbar at the top, which contained back and forward options.

Shell Technology Preview/NewShell
NewShell is a pack that adds the new NT4 (alpha) shell to NT 3.51. Only two builds of NewShell, build 1054 and 1057 has been leaked as of 2021. NewShell's UI is similar to that of Windows NT 4.0 build 1130.1. It causes the kernel version to jump to NT 4.0. A final version of NewShell was never released. Its purpose was to test the Windows 95-style shell on Windows NT so it could later be ported to the upcoming NT 4.0.

Windows 98/Me/2000
Windows 98 substantially refined the Explorer UI to be integrated with Internet Explorer, and to feature a bar at the left side containing information about the selected folder or file. This update was known as the Windows Desktop Update. A toolbar was also included by default, which allowed users to easily navigate the UI. Windows 98 also introduced Active Desktop, which allowed web content to be placed on the desktop. Animations were added to context menus, and title bars could now be customised with two-colour gradients. The taskbar received the ability to place toolbars, which was later removed in Windows 11. Windows Me added a minor change to Control Panel, which grouped the most frequently used settings into a category view. The classic icon view was still available, however.

These changes were later ported to the NT line with Windows 2000, and installing Internet Explorer 4 on Windows 95 or Windows NT 4.0 would enable a web-based desktop UI similar to later Windows versions.

Windows XP
Windows XP introduced major changes to the Explorer UI to make the experience easier and more intuitive for new users. A common tasks pane was introduced, but the old web view pane could be enabled with a registry tweak. The common tasks pane provided easy access to tasks such as deleting files, and it also provided quick access to other folders. A new Filmstrip view has been introduced, which provided quick previews of image files. A new Search UI was introduced featuring the Search Companion. This UI design would now automatically adapt to the selected theme.

Windows Vista
Windows Vista saw many changes to Explorer. The common tasks pane from Windows XP was removed, and replaced by a new command bar at the top. The address bar was removed, and replaced by a new "breadcrumbs" bar that was easier to use than the previous UI. The right side of the window featured a navigation tree, providing access to user folders, but hiding other folders away in a "Folders" drawer. The Filmstrip view was removed and replaced by a new preview pane. Drives would show their free amount of space in a bar that would appear under the icon. The classic menu bar could still be enabled, and the navigation tree could be hidden.

Windows 7
Windows 7 made minor changes to the Explorer UI. The icons in the command bar were removed, and all folders were now shown in the navigation pane as opposed to them being in a separate drawer. Libraries were added, which was a type of folder that would display the contents of the folders contained in it, similar to symbolic links.

Windows 8
Windows 8 replaced the command bar with a much more advanced Ribbon UI, which had been previously used since Office 2007. It introduced smart tabs, which would automatically appear when browsing a certain folder. Windows 8.1 later removed the ability to show Libraries by default, and added the user folders to This PC.

Windows 10
Windows 10 introduced updated icons and a new "Quick access" menu, which provided easy access to frequent files and folders.

Windows 10X
Windows 10X would have replaced the classic File Explorer with a new Files app, which would display files backed up to OneDrive instead of being stored locally on the device.