MIQ: Medical Image Quick Look

MIQ is a lightweight macOS QuickLook extension for medical volume images. Press Space on a supported file in Finder to instantly get an interactive orthogonal slice view alongside a metadata panel. MIQ is meant for a quick look: it prioritizes speed and ease of use over advanced visualization, and is not meant to replace dedicated medical image viewers. A Windows counterpart, MIQ-Win, is also available.

See it in action in the short video at the bottom of this page.

Main Features and Supported Formats

• Instant, interactive preview — press Space for the 2×2 orthogonal slice and metadata view
• Built for speed — memory-mapping, partial decompression, and network volumes read only what's needed for the first preview
• 4D support — scrub through timepoints/volumes interactively
• Segmentation coloring — including automatic label-color detection for FreeSurfer-style parcellations
• Finder thumbnails — optional file-icon slice previews while browsing
• Fully configurable — orientation display, intensity windowing, label colors, and metadata panel content/order, all from the main app

Supported formats:

• ✅ NIfTI-1 & NIfTI-2 — .nii, .nii.gz
• ✅ FreeSurfer — .mgh, .mgz, .mgh.gz
• ✅ MRtrix — .mif, .mif.gz
• ✅ NRRD — .nrrd (only single-file variant; not detached .nhdr)
• ✅ ITK MetaImage — .mha (only single-file variant; not detached .mhd)

All formats are supported uncompressed and gzip-compressed.

Installation & Updates

The app and extension can be installed manually or via the package manager Homebrew.

The app is a universal binary for Apple Silicon (arm64) and Intel (x86_64) Macs and has been tested on macOS 14 (Sonoma), 15 (Sequoia), 26 (Tahoe) and 27 (Golden Gate).

Manual installation

1. 👉 Download the latest release (MIQ.app.zip)
2. Unzip and move MIQ.app to your /Applications folder.
3. Open MIQ.app at least once to register the Quick Look extension.
4. Press Space on any supported file in Finder.
5. Optional: Customize the preview in the MIQ app.

Updating

MIQ updates itself. Open the MIQ app and choose MIQ → Check for Updates…, or leave Check for updates automatically enabled in the app's General pane (on by default).

Automatic checks happen only while the main app is open. So that you don't miss updates once your settings are made, previews show a reminder below the metadata when MIQ hasn't checked for 30 days; opening the app runs the check and clears it. Previews never connect to the internet themselves. Turn the reminder off with Remind me in previews to check for updates in the General pane.

Installation via Homebrew

1. Install on the command line:

   brew tap marcoduering/miq
   brew trust --cask marcoduering/miq/miq
   brew install --cask miq

2. Open MIQ.app (in /Applications) at least once to register the Quick Look extension.

3. Press Space on any supported file in Finder.

4. Optional: Customize the preview in the MIQ app.

Updating via Homebrew

The cask is marked auto_updates, so the app updates itself (see above). To update through Homebrew instead:

brew update
brew upgrade --cask miq --greedy

Usage

Customization

Use the MIQ app to tailor the preview, metadata panel and thumbnails. Live examples show the effect of each setting as you change it. The Controls pane lists all gestures for the interactive preview.

Orientation

By default, MIQ displays data as stored on disk, without reorienting. Images may appear upside down, mirrored, or rotated depending on acquisition. This is by design, so you can inspect the raw data "as is". Optional settings reorient to Neurological or Radiological view. Either way, the R/L, A/P and S/I letters at the image edges show the real anatomical directions, even when the image looks flipped or rotated.

Privacy

Everything runs locally on your Mac, and MIQ collects no telemetry. The only network access is the main app's update check (and the download, if you install an update); the Quick Look and thumbnail extensions have no network access at all. File names and paths are redacted in the system log. MIQ itself writes no copies of your images; but if you turn on Finder thumbnails (off by default), macOS stores them in its thumbnail cache, where they can remain after a file is moved or deleted until macOS prunes the cache or you clear it: use Clear thumbnail cache in MIQ's Thumbnails settings, or run qlmanage -r cache && killall com.apple.quicklook.ThumbnailsAgent Finder in Terminal. See the privacy policy for details.

Troubleshooting

.gz File Handling

macOS Quick Look routes files to extensions by file name suffix. Several kinds of tools, including archive utilities, source-code viewers, and format-specific extensions like MIQ, need to claim the broad .gz suffix to support compound extensions such as .nii.gz/.mif.gz. When more than one installed extension claims .gz, which one macOS shows isn't always consistent; this is general Quick Look behavior, not specific to MIQ. If a gzip-compressed file isn't opening with MIQ's preview, try deactivating other .gz-handling extensions.

Active Development

MIQ is free and open source, in active development, and was created with the support of AI coding agents. Report issues or feature suggestions via GitHub Issues, or see CONTRIBUTING.md to contribute. If MIQ is useful to you, consider sponsoring the project (entirely optional, always appreciated).

Disclaimer & License

MIQ is provided "as is" under MIT License, without warranty of any kind, express or implied. The authors and contributors accept no liability whatsoever for any direct, indirect, incidental, special, or consequential damages arising from the use or inability to use this software, including but not limited to data loss, incorrect image rendering, or any decisions made on the basis of previews generated by this tool.

Caution

This software is not a medical device and is not intended for diagnostic use. It is a developer and researcher convenience tool only. Do not use it to make clinical decisions.

See it in action

MIQ.mp4