Microsoftは3月26日(現地時間)、Windows 11 Version 25H2/24H2用のプレビューアップデートKB5079391を公開しました。オプション扱いの更新プログラム(プレビュー版)で、多数の不具合が修正されています。Windows Updateの「更新プログラムのチェック」を利用するか、Microsoft Update Catalogからファイルをダウンロードすることで、手動でインストールすることができます。March 26, 2026—KB5079391 (OS Builds 26200.8116 and 26100.8116) PreviewWindows 11 Version 25H2/24H2用の更新プログラムKB5079391には、1000Hzを超える超高リフレッシュレート対応や、ファイルエクスプローラーの改善、Smart App Controlの再有効化対応など、OS全体にわたる多くの新機能と改善が含まれています。リリースノートは以下の通りです。ハイライトGradual rolloutThe following summary outlines features from AI-powered Windows 11 PC experiences, along with improvements and fixes. The bold text within the brackets indicates the item or area of the change.Windows 11 PC experiencesThis section highlights some new features and enhancements for Windows 11 PCs, including AI-powered capabilities, continuous innovation, and performance improvements.[Narrator] New! 1 Narrator provides rich image descriptions on Copilot+ PCs and now works with Copilot on all Windows 11 devices. Press Narrator key + Ctrl + D to describe the focused image or Narrator key + Ctrl + S to describe the full screen. Copilot opens with the image ready, allowing you to enter a prompt for a customized description. The image is shared only after you choose to describe it. On Copilot+ PCs, Narrator gives instant, on‑device descriptions, and you can select Ask Copilot for more detail.[Smart App Control] New! You can turn Smart App Control (SAC) on or off without needing a clean install. To make changes, go to Settings > Windows Security > App & Browser Control > Smart App Control settings. When turned on, SAC helps block untrusted or potentially harmful apps. To learn more, see App & Browser Control in the Windows Security App. This feature was previously disclosed in January 2026 (KB5074105) and is now beginning to roll out.[Account Settings] New! Microsoft 365 Family subscribers can upgrade to a different Microsoft 365 plan from Settings > Accounts. To remove the upgrade option, turn off Suggested content in Settings. New! This update improves the design of the dialog boxes in Settings > Accounts > Other users to match the modern Windows look and support dark mode. The visibility of the dialog box option depends on whether the device has a domain joined work or school account.[Input]New! The Pen settings page includes refinements to the pen tail button options. The new “Same as Copilot key” option enables the pen tail button to open the same app as the Copilot key.[Settings] New! The Settings About page (Settings > About) has been improved to provide a more structured and intuitive experience, offering clearer device specifications and easier navigation to related device components, including quick access to Storage settings. New! 2 The device information card on the Settings Home page simplifies key device specifications and improves consistency across the end-to-end flow from the Home Card to the Settings > System > About page, making information easier to scan and understand.This update improves the reliability and performance of opening the Home in Settings.This update improves the reliability of downloading required updates when you’re prompted in Settings > System > Advanced.[File Explorer] This update improves the File Explorer experience.You can more reliability unblock files downloaded from the internet in order to preview them in File Explorer.You can use Voice Typing (Windows logo key + H) when renaming a file in File Explorer.You can now sort the permissions entries in the Advanced Security Settings window for a folder in File Explorer by Principal.[Display] This update includes Display reliability improvements.Monitors can now report refresh rates higher than 1000 Hz.When you use a native USB4 monitor connection, the USB controller can now enter its lowest power level while the PC is sleeping, which helps save battery life.Auto rotation reliability has improved after resuming from sleep.HDR reliability has improved for displays with non-compliant DisplayID 2.0 blocks.Monitors with DisplayID now report a more accurate size when the WMI monitor APIs are used.[Printing] Updated downlevel baseline support for printer connections to be Windows 10, version 1607 and Windows Server 2016 (Build 14393).[Safe mode] This update improves the reliability of loading taskbar components in safe mode.[Voice Access] This update improves how numbers are detected and written when using Voice Access in English.[Start menu] This update improves the reliability of applying the Start menu layout through Group Policy when desktopAppLink is present in the JSON.[Remote Desktop] The Set-RDSessionCollectionConfiguration PowerShell command now recognizes DisableSeamlessLanguageBar.[Audio] This update improves how short MIDI messages are handled in cases where an application is initialized without providing long message buffers.[System File Checker] This update removes an extraneous error message you might unexpectedly see when running sfc /scannow.[Windows Hello] This update improves Windows Hello Fingerprint reliability for certain devices. 1 Functionality will vary by device and market. 2 Availability will vary by device and market. Normal rolloutThis non-security update includes quality improvements. The following summary outlines key issues addressed by the KB update after you install it. Also, included are available new features. The bold text within the brackets indicates the item or area of the change.[Application Control for Business] Improved: This update improves Application ID tagging in Application Control for Business policies. With this update, the system identifies which apps should receive tags more accurately and behaves more reliably.[Narrator] This update improves the Natural Voices experience in Narrator. It also makes Natural Voices setup more reliable.[Performance & Reliability] This update improves stability in Windows Recovery Environment (Windows RE) when you run x64 apps on ARM64 devices. These apps run more smoothly and respond as expected.[Windows Update Deployment (known issue)] Fixed: This update addresses an issue in Windows 11, version 25H2, where updates installed using the Windows Update Standalone Installer (WUSA) might fail with error code ERROR_BAD_PATHNAME. This issue can occur when you double-click a .msu file or run WUSA from a network share that contains multiple .msu files.If you installed earlier updates, your device downloads and installs only the new updates contained in this package.既知の不具合更新プログラムには既知の不具合は存在しません。更新プログラムはWindows Updateの他、Microsoft Update Catalogを利用してインストールすることができます。