Gazelle is a Microsoft Research prototype web browser constructed as a multi-principal OS (empahsis on research and prototype).  From the Gazelle Microsoft Research Technical Report: Gazelle’s Browser Kernel is an operating system that exclusively manages resource protection and sharing across web site principals. This construction exposes intricate design issues that no previous work has identified, such as legacy protection of cross-origin script source, and cross-principal, cross-process display and events protection.

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