Windows 11 supports passkeys, but only in the most basic way imaginable. But that's about to change. Microsoft says.

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In the latest Beta version of Windows 11, there’s a new toggle in the Taskbar section of Windows Settings that lets you Show smaller taskbar buttons with options for Always, Never, and When taskbar is full. (As of this writing, the setting isn’t fully working as intended.)

If you're currently using any version of Windows other than Windows 11, then your system is either already unsupported (Windows XP, Vista, 7, 8.1), or soon to become unsupported (Windows 10). And Microsoft's best advice for anyone in that situation is "move to Windows 11 by buying a new PC".