Mio: a tiny open-source macOS screenshot utility built with SwiftUI + ScreenCaptureKit

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Hi everyone,

I’ve been building Mio, a small open-source macOS screenshot utility written in Swift 6.3 with SwiftUI and ScreenCaptureKit.

The goal is simple: press a hotkey, freeze the current screen state, select a window / region / display, optionally annotate it, and keep everything local. No account, no telemetry, no network access.

Repo:

A few implementation details that may be interesting to this community:

  • ScreenCaptureKit is used for display and window capture.
  • The capture/output path is organized around Swift actors.
  • Window screenshots use transparent output so rounded corners are preserved instead of cropping desktop wallpaper into the corners.
  • The editor stores vector-like drawing commands instead of repeatedly mutating bitmap state.
  • The app is menu-bar only, with SwiftUI used for the menu, settings, onboarding, and editor UI.

Current limitations:

  • macOS 26+.
  • Apple Silicon only.
  • Early public release; feedback and bug reports are welcome.

I’d especially appreciate feedback on the SwiftUI/AppKit boundary and the concurrency design around the capture pipeline.

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