FastImage

FastImage is a tiny native AppKit/SwiftUI image viewer for macOS. It opens images quickly, keeps the interface out of the way, and has no third-party dependencies.

Download and install

Download the latest universal macOS release from GitHub Releases. Open the DMG, then drag FastImage to Applications. It supports both Apple silicon and Intel Macs running macOS 13 or newer.

The current downloadable build is not notarized because the project does not yet have a Developer ID Application certificate. On first launch, try opening FastImage once, then go to System Settings → Privacy & Security and click Open Anyway. This exception is required only once for that build.

Features

• Sony RAW (.arw) support
• Standard image formats supported by macOS, including JPEG, PNG, TIFF, HEIC, GIF, BMP, and WebP
• Open from Finder or drag and drop into the window
• Browse every supported image in the current folder with the left and right arrow keys
• Point-anchored mouse-wheel zoom, direct mouse dragging, and double-click fit-to-window
• Lightweight JPEG/PNG crop tool with draggable edge/corner handles and rule-of-thirds guides
• Memory-efficient crop undo/redo reconstructed from the original image
• One-command JPEG/PNG overwrite save
• Image-first startup, eager background JPEG/PNG decoding, and background folder scanning keep opening fast and responsive
• Strict three-image cache keeps navigation fast without letting memory usage drift upward

Sony RAW support

Sony .arw files are decoded with Apple's built-in ImageIO framework. FastImage uses the camera's embedded preview when available, so a large RAW file opens quickly without bundling a heavyweight RAW library or performing a full-resolution demosaic just to fit the image on screen.

This is intentionally a fast viewing path, not a RAW development or editing pipeline. Sony RAW files and formats other than JPEG/PNG are view-only in FastImage.

Crop and save

Press K to enter crop mode. Drag any edge or corner handle, drag inside the selection to move it, or drag outside it to draw a new selection. Press Enter to apply the crop or Esc to cancel it.

For JPEG and PNG files, the toolbar save button and Command-S atomically overwrite the original without a confirmation dialog. Other formats remain view-only.

Undo and redo keep only crop geometry plus the original source image, rather than retaining a full-resolution raster for every history step. Undo remains available after saving, so an overwritten crop can still be restored and saved back during the same editing session.

Controls

• Left Arrow / Right Arrow: previous or next image
• Click an image point, then use the mouse wheel: zoom around that point
• Drag: pan the image at any zoom level
• Double-click: fit the image to the window
• K: enter or cancel crop mode
• Enter: apply the crop
• Esc: cancel the crop
• Command-Z: undo the last applied crop
• Shift-Command-Z: redo the crop
• Command-S: overwrite the original image with applied edits

Requirements

• macOS 13 or newer
• Xcode 14 or newer to build from source

Build

Open FastImage.xcodeproj in Xcode and build the FastImage scheme. The project uses only macOS system frameworks.

To produce the same universal ZIP, DMG, and checksum file used by GitHub Releases:

./scripts/build-release.sh 1.0.0

Release builds use the hardened runtime and are ad-hoc signed. A tag such as v1.0.0 runs the GitHub release workflow and uploads the generated artifacts.