Matlab viewer for macOS

MAT File Viewer quick looks, previews and opens MATLAB (.mat) files directly and lays them out the way MATLAB's own Workspace does: every variable in the file with its size and class. Open one to see it. Matrices show as numbers, as a heatmap, or, when an array is really an image, as the picture it is. Cell arrays and structs open with a double click, as deep as they nest. A struct array reads as a table of records, and a struct of equal-length columns (the classic way of logging data) opens as one table you can sort and filter. N-dimensional arrays page through one slice at a time, and sparse matrices show their pattern of nonzeros.

Thumbnails and Quick Look work for .mat files right in your file browser.

".mat" is actually four formats wearing one extension. Level 4 files are a bare run of matrices from the early nineties. Versions 6 and 7 are a tagged stream of typed elements, each variable compressed on its own, in whichever byte order the saving machine used (old Solaris files are big-endian). And version 7.3, the format MATLAB uses for anything large, is HDF5 behind a 512-byte header. So the app includes its own HDF5 reader, written from the published file format specification: superblocks, object headers, B-trees of chunked and compressed data, a global heap for variable-length values. On top of that sit MATLAB's own conventions: a hidden group of referenced objects behind every cell array, annotations saying what each dataset really is, and dimensions stored backwards, because MATLAB is column-major and HDF5 row-major.

Tested with files saved by MATLAB 4.2 to 2025, including big-endian files from Solaris, decoded to a canonical text form and compared line for line with scipy and h5py.

Features

Quick Look support for every version of the format:

• MAT v4 - the original matrix format
• MAT v6 and v7 - MATLAB's default, compressed or not, in either byte order
• MAT v7.3 - HDF5 based, used for large variables

Each allows:

• Finder thumbnails and Quick Look
• A workspace view: every variable with its size and class
• Cell arrays and structs open with a double click, as deep as they nest
• Struct arrays as tables of records, and structs of equal-length columns as one table
• Matrices as numbers or heatmaps, image arrays as pictures, sparse matrices as their pattern
• N-dimensional arrays page by page; complex, int64 and logical values shown exactly
• Sort by any column; filter rows
• Read-only - your source files are unchanged
• 100% on-device, no accounts, universal binary

Pro features via the Mac App Store.

Pro Features (available as IAP from Mac App Store)

Free app with an optional Pro unlock. MAT Pro adds:

• Descriptive statistics: n, missing, mean, SD, min, median, max for every column
• Pairwise correlation matrix (Pearson r)
• Chart builder: histograms and banded means, as bars or lines
• Scatter plots with a least-squares fit and r / r²
• CSV export of matrices, struct arrays and tables

Known issues

MATLAB's newer object types, such as string, table and datetime, are stored in an undocumented internal format. They are listed by name and class, but their contents are not decoded yet.

MATLAB is a registered trademark of The MathWorks, Inc. MAT File Viewer is an independent app, not affiliated with or endorsed by MathWorks.

Requirements

Universal binary, so it runs on both Intel and Apple Silicon Macs.

• macOS 14 (Sonoma) or later
• Intel Mac or Apple Silicon (M1 or newer)

Installation

Download the file, unzip it, and copy it into your Applications folder. Open it once and it registers the Quick Look handler itself. Instructions are included with the download.

Apps downloaded here are signed by Apple, so you shouldn't see any Gatekeeper warnings.

Licence

What you may do: install and use the software, at no cost, on any Mac you own or control, for personal or business purposes.

What you may not do: sell, rent, lease, sublicense or otherwise charge anyone for the software; redistribute, repackage, bundle or host it for download (please point people at the official download page instead); or modify, adapt, translate, reverse-engineer, decompile or disassemble it, except to the limited extent applicable law expressly permits.

The software is licensed, not sold. All rights not expressly granted above are reserved by the copyright holder, who may offer future or paid versions under different terms.

Privacy

100% on-device. No accounts, no tracking, never connects to the internet, collects no data whatsoever.

Feedback

Please contact me with any feedback, issues, suggestions or requests!