expert

AppContainers & capabilities

Modern app isolation using AppContainer SIDs and capability grants.

What you should already know

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Why it matters

Store/UWP-style apps and many modern browsers rely on AppContainer isolation beyond classic DACLs and integrity.

Mental model

An AppContainer is a low-trust box. Capabilities are fine-grained holes punched in that box for network, files, or devices.

How it works

  1. 1Processes run with an AppContainer SID plus optional capability SIDs.
  2. 2Resource access checks combine DACL, integrity, and capability policy.
  3. 3Brokers and runtime packages declare which capabilities an app may request.

Key terms

AppContainer
A sandbox identity used for modern application isolation.
Capability SID
A grant that allows a specific class of access for an AppContainer.

A Store app that cannot touch arbitrary files

Even if a folder DACL looks permissive, the app may lack the broad-filesystem capability and remain blocked.

Common misconception

AppContainer is not UAC. It is an additional isolation layer often combined with MIC and brokered access.

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