Windows 10 (original release)

This article is about the original release of Windows 10 from July 2015. For the overall operating system series, see Windows 10.

Windows 10 (codenamed Threshold; retroactively referred to as version 1507 in documentation) is the successor to Windows 8.1 and the first release of the Windows 10 series, released on 29 July 2015 as a free upgrade for Windows 7 and Windows 8.x users until 29 July 2016 through the Get Windows 10 app. It was intended to address some of the complaints that were made in response to the user interface in Windows 8 and Windows 8.1. It has gained largely positive reviews and has easily exceeded the market share that Windows 8 gained in the same period.

Very early documents refer to this version as Windows 8.2, Windows 9, or Windows TH. According to an unverified rumor, the name "Windows 9" was rejected due to certain apps interpreting an operating system name beginning with that string as belonging to the Windows 9x series. It is more likely that the name change was due to marketing potential. Microsoft explained the skip from number 8 to 10 as reinforcing the importance of Windows 10 as the last major version of Windows, although the company would later break this promise with the release of Windows 11 in 2021.

The Windows Insider Program was introduced with this version, which boosted the company's engagement with its beta testers as well as distributing new releases more frequently than the prior beta testing initiatives. The Insider program was also the first time Windows Update was used to publicly distribute full new builds of the operating system, as opposed to simple patches applied on top of the same build.

Interface
The desktop interface received an update after being unchanged since Windows 7. The taskbar received a design overhaul with the addition of a search bar, an Action Center button that allows the user to view notifications, and a Task View button that allows users to display all open windows and switch between them and it also allows users to create virtual desktop workspaces. The DirectUI-based Start screen was removed in favor of a revamped Start menu which is divided into two columns and is based on XAML. The left side of the menu lists links to frequently used applications and user folders. The All Apps button allows the user to view a list of programs installed on the computer. The right side of the menu features titles that can be pinned and resized. The Start menu can also be resized or be placed into a full-screen UI resembling the Windows 8 Start screen which scrolls vertically instead of horizontally.

The Charms bar was removed completely and replaced by the Action Center, which displays notifications and settings toggles which can be accessed by clicking the Action Center icon in the system tray or swiping from the right side of the screen.

The operating system was redesigned to adapt its UI based on the type of device being used and available input methods. It offers two separate UI modes which include the regular UI optimized for desktops and a Tablet mode designed for touchscreen devices. Users can switch between the two modes and the OS can prompt or automatically switch the UI mode when certain events occur, such as disabling the Tablet UI on a tablet if a keyboard or mouse is plugged in, or when a 2-in-1 PC is switched to its laptop state. In Tablet mode, programs open maximized, and the taskbar is simplified for touchscreen use by adding a back button and hiding the buttons of opened and pinned programs by default, the Task View button is used to switch between programs and the Start menu will also automatically open in full-screen mode.

The search box also incorporates Cortana, an intelligent personal assistant which supports text and voice input. It features functionality such as integration with Bing, setting reminders, a Notebook feature for managing personal information, as well as searching for files, playing music, launching applications and setting reminders or sending emails.

Windows Store apps were overhauled to open in regular desktop windows rather than opening up in full-screen mode in the regular UI. The app commands which were previously available on the Charms bar are accessed from an app command menu on their title bar.

The login screen was updated to support improved multi-factor authentication technology through Windows Hello which allows users with a supported camera to login with iris or face recognition. The UI design of the login screen and lock screen was also revamped.

The Quick access menu was added to File Explorer to provide quick and easy access to frequently used files and folders. Many system icons were also revamped to follow the Metro design language as well.

The PC Settings app was completely revamped and renamed to simply Settings. It includes more options that were exclusive to the Control Panel such as Windows Update. Starting with this version of Windows, the Control Panel was deprecated as Microsoft started to move settings from the Control Panel to the Settings app.

Windows Update received major changes to its overall functionality and operation. Windows Update no longers allows the manual installation of updates and all updates are now downloaded and installed automatically regardless of type. Users can no longer postpone the mandatory restart for updates as they are only given the option to reboot automatically to install the updates when the system is not being used, or be notified to schedule the reboot. The use of Windows Update is also now mandatory as Windows Update along automatic updates can no longer be turned off within the UI. Cumulative updates were also introduced which packages separate updates into a single update package, mitigating the need for multiple restarts and reducing the number of downloads needed. This means that it is no longer possible to download and install updates that fix individual problems.

Windows Update ESD listing
See here for a list of Windows 10 ESD files that have been gathered from the Windows Update infrastructure.''

Technical Preview
The Technical Preview was the first phase of the Windows Insider program. The first official build released was 9841, and the last official build released during this phase was build 10061.

Insider Preview
This phase of development began with build 10074, which was a quality build, at least going by the standards set by 10041 and 10049. The final phase of TH1 Insider Preview development ended with build 10166, which was extremely close to the RTM build, build 10240.