Windows App SDK 2.6.6 Experimental Adds Hierarchical TableView and Chart Accessibility

Where this release sits​

The release notes say 2.6.6-experimental follows Windows App SDK 2.6.5 stable and carries over that release's changes. The tag is v2.6.6-exp, and the package is Microsoft.WindowsAppSDK version 2.6.6-experimental on NuGet.

Microsoft's release-channel documentation explains why the label matters. The experimental channel is for early-stage features under active development, and it is published as needed to gather feedback on prototypes and early designs. Microsoft's developer news page also warns that experimental WinUI controls might change or be removed, and aren't intended for production apps.

Microsoft's docs list the stable baseline, 2.6.5, as released on 11/02/2026. Some Microsoft Learn pages were still showing 2.5.4-experimental as the latest experimental build when I searched, so they may lag behind this release. The Learn release notes already carry an entry for this build, which they date November 6, 2026. GitHub shows the release at 01:43 UTC on November 7.

TableView gets hierarchy and live updates​

TableView is the biggest change in this release. According to the release notes and the Learn documentation:

• Hierarchy. TableViewSource.ParentBy builds a row hierarchy from item and parent keys. ClearParentBy removes it. TableViewRow exposes Level, IsExpandable, and IsExpanded. TableView.ExpandAllRows and CollapseAllRows expand or collapse the whole tree.
• Live shaping. TableViewSource.IsLiveShaping is opt-in. When enabled, sorting, filtering, grouping, and hierarchy update automatically as item properties change.
• Context menus. TableViewColumn.CellContextFlyout and HeaderContextFlyout let apps supply menus for cells and column headers.
• Accessibility and polish. TableViewRowAutomationPeer exposes row expansion and collapse to UI Automation clients. High-contrast rendering, column resizing, and column headers also improve.

For line-of-business apps this matters. Tree-style data grids, such as asset inventories, org charts, or ticket hierarchies, usually need a third-party control or a lot of custom code. Live shaping also addresses a common complaint about sortable lists, which is that they go stale when a property changes.

The release notes give no performance numbers and no details on how live shaping is implemented. Test it against your own data volumes before you commit to it.

Chart accessibility​

ChartAutomationPeer and chart parts add UI Automation support to the experimental Chart control. That is good news for screen-reader users. The notes don't list which automation patterns or chart types are covered, so check with Narrator and other assistive tools before you rely on it.

Zero-copy resource access​

ResourceCandidate.ValueAsMemoryBuffer gives access to embedded resource bytes without copying them. For native code, the new MrmLoadStringOrEmbeddedResourceAsView and MrmLoadStringOrEmbeddedResourceByIndexAsView APIs provide resource views for C and C++ callers. Microsoft Learn tags this change with the runtime-compatibility identifier ResourceCandidate_ValueAsMemoryBuffer.

The sources claim no measured memory or speed gains, so treat this as an API capability rather than a benchmark result. They also don't spell out lifetime or ownership rules for the returned views. Read the API proposal before you hold on to one.

Scrolling content outside bounds​

ScrollView.CanContentRenderOutsideBounds and ScrollPresenter.CanContentRenderOutsideBounds let content draw beyond the viewport's clipping. Both default to false, so existing layouts won't change unless you opt in. This should help with shadows, glows, and overhanging visuals that the clip currently cuts off.

Video scaling options​

The video scaler is the Video Super Resolution API. Microsoft describes Microsoft.Windows.AI.Video.VideoScaler as an AI upscaler optimized for streams featuring people in conversation, and it first appeared in 2.2.0. This release adds:

• A VideoScaler.CreateAsync overload that takes VideoScalerCreationOptions. Apps can request an execution device, a video scenario, and a performance or quality preference.
• VideoScalerOptions.InputColorMatrix and InputColorRange. Apps use them to describe input frames as BT.601 or BT.709, with full or limited color range.

Declaring the color encoding matters because a mismatch can shift colors. The notes don't list supported devices, scenarios, or formats, and they report no quality improvement.

Bug fixes and their compatibility switches​

Each fix carries a runtime-compatibility identifier, which is useful when you track behavior changes.

The window-size fix and the 65,535-pixel cap are the ones to check if your app saves or restores window geometry. The OptimizeApplyStyles and flyout fixes remove crashes and visual glitches that were hard to work around.

What 2.6.5 stable already fixed​

Because this build rolls up 2.6.5, it inherits those fixes. According to Microsoft Learn:

• Rendering corruption on systems with multiple graphics adapters or monitors.
• An E_NOINTERFACE crash when enabling the System Composition Engine on Windows builds that lack the required interfaces. The runtime now uses the lifted compositor on those builds.
• Window backgrounds and GDI controls becoming unexpectedly transparent on Windows 10, including apps hosting XAML islands.
• App-extension registration metadata generation returning E_NOTIMPL, which could stop packaged apps from installing.

The 2.6.4 system-backdrop change was also reverted because of wrong-thread exceptions. System backdrops for content islands and XAML windows are not supported with the System Composition Engine in this release.

Should you try it?​

Reasons to try it:

• You're building data-heavy WinUI 3 apps and want to evaluate hierarchical TableView.
• You build accessible apps and want early automation support for charts and ink.
• You work with native resources or video pipelines and want to test the new APIs early.

Reasons to wait:

• You ship production software. Experimental APIs can change or disappear, and Microsoft says as much.
• You need a stated Windows minimum for these specific features. The notes don't give one, so verify on your target builds.

A safe way to evaluate it is to put the experimental package in a branch or a test project. Install it through NuGet, then run the WinUI Gallery to see the control updates. Microsoft's upgrade guidance for earlier experimental builds also warns that experimental packages can carry higher version numbers than the stable ones. That can cause NuGet downgrade errors, and the fix is to uninstall the experimental package before you move to stable.

Bottom line​

2.6.6-experimental is a feature-preview drop and the broad changes are mostly accessibility and data-UI work. TableView hierarchy and live shaping stand out, and the window-size and ink fixes round things out. Microsoft hasn't published performance data or migration guidance for the new APIs, so test them yourself.

Correction (November 6, 2026): An earlier version of this article said the VideoScaler API first appeared in Windows App SDK 2.6.4. It actually debuted in 2.2.0, released June 9, 2026, per Microsoft's Windows App SDK release notes.