PortalBox

PortalBox is a macOS application that allows sharing specific screen regions in Zoom, Google Meet, Teams and other platforms. Draw a rectangle over the desired area to create an independent preview window containing only the selected content. This window can be shared as a video source in any video conferencing application. The program operates from the menu bar and provides controls to pause the stream, adjust the capture area and manage multiple monitors.

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• Rectangular region selection. Allows drawing a rectangle over any area of the main or secondary screen. The selection defines the capture boundaries. The rectangle features size handles on each corner and edge for precise dimensional adjustments. Capture is strictly limited to the content within these boundaries.
• Floating preview window. Generates an independent window that displays the content of the selected region in real-time. This window can be repositioned anywhere on the desktop. Its size and aspect ratio correspond to the defined capture area. The window serves as the video source for meeting applications.
• Integration with meeting applications. The PortalBox preview window is detected as a virtual camera or screen source in Zoom, Microsoft Teams, Google Meet and similar applications. Users select "PortalBox" as the video source in the meeting app's screen sharing settings. This broadcasts only the content of the defined region.
• Instant pause mode. Interrupts the preview stream without closing the selection region. The preview window displays the last captured frame until resumed. The feature is activated from the menu bar icon or via a configurable global keyboard shortcut. The system does not capture or process new images while paused.
• Support for multiple monitors. The selection tool can move between all screens connected to the macOS system. Allows capturing regions on primary, secondary monitors or ultra-wide screen setups. The preview window accurately reflects the source screen's resolution and scale.
• Precise adjustment with handles. The edges of the selection rectangle include interactive control points. Dragging these points modifies the width and height of the capture area. The system provides visual guides and magnetic snapping to align the selection with window edges or other interface elements.
• Window selection shortcut. Offers a quick method to define the capture area based on the boundaries of an open application window. When activating this mode, the user clicks on a window and PortalBox automatically adjusts the selection rectangle to frame it completely. Manual adjustments can then be made.
• Controls from the menu bar. An icon located in the macOS menu bar provides access to all main functions. From this menu, you start or stop capture, activate pause mode, redefine the selection region and access program preferences. The current status (active/paused) is indicated on the icon.
• Global keyboard shortcuts configuration. Allows assigning custom key combinations for frequent actions, mainly pausing/resuming capture. These shortcuts work system-wide, even when PortalBox is not the active application. Configuration is done in the application's preferences panel.
• Defined privacy architecture. The capture engine processes only the pixels contained within the selection rectangle. Video data is not stored on disk, not uploaded to remote servers, and not accessible to other system processes beyond streaming to the preview window. Capture stops immediately when the application is closed.

PortalBox development began in 2025. The application was created by an independent developer who identified the need for sharing screen regions during virtual meetings. The program is written in Swift and uses native macOS frameworks such as AppKit and AVFoundation for screen capture and window management. Early versions focused on the basic functionality of region selection and preview window generation.

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