ImageOptim is a free, open-source Mac application that compresses PNG, JPEG, and GIF files by stripping unnecessary metadata and applying best-in-class encoding algorithms — all through a dead-simple drag-and-drop interface.
What is ImageOptim?
ImageOptim is a lossless and near-lossless image compression tool for macOS, built by developer Kornel Lesiński. It acts as a front-end for a battery of proven open-source optimizers — MozJPEG, pngcrush, Zopfli, and others — orchestrating them in sequence so you never have to touch a command line. Drop an image (or a whole folder) onto the window, and within seconds the file is smaller, the pixels are untouched, and the original is overwritten in place.
I first reached for ImageOptim after noticing my web projects were hauling multi-megabyte screenshots into production. A batch of thirty PNGs that collectively weighed 48 MB came back at 31 MB — clean, with no visible degradation at any zoom level. It has sat in my Dock ever since.
What does ImageOptim do best?
ImageOptim excels at squeezing every last redundant byte out of images without asking you to make quality trade-offs. Where Photoshop's "Save for Web" leaves Exif GPS tags, color profiles nobody requested, and bloated ICC data intact, ImageOptim strips all of it — while simultaneously re-encoding the pixel data through multiple competing codecs and keeping whichever result is smallest.
- Lossless compression by default — pixel data is mathematically identical to the original.
- Optional lossy mode — dial in an acceptable quality floor (e.g. 80%) for dramatic additional savings on JPEGs and PNGs with a quality slider buried in Preferences.
- Metadata removal — Exif, IPTC, XMP, GPS coordinates, colour profiles, and comments are all stripped unless you explicitly opt out.
- Folder-recursive processing — drop an entire assets directory and every eligible file inside it is processed.
- Progress transparency — every file gets a percentage-saved badge, so you can immediately spot the outliers worth investigating.
Is ImageOptim free?
Yes — ImageOptim is completely free to download and use on macOS, with no nag screens, no feature gates, and no subscription. The source code is public on GitHub under the terms of the GPL. Kornel accepts donations, but the app will never prompt you for them.
There is a separate commercial ImageOptim API for server-side or CI pipeline use, but the desktop app itself has always been and remains gratis.
Who should use ImageOptim?
Any Mac user who puts images on the web should have it installed. That covers web developers, bloggers, designers prepping assets for Figma or Sketch handoff, and photographers uploading portfolio work. It is especially valuable for anyone maintaining a static site or e-commerce store where image weight directly affects Core Web Vitals scores and hosting bandwidth costs.
Where ImageOptim is less ideal: if you need to convert between formats (say, PNG to WebP or AVIF), you will need a complementary tool like Squoosh or cwebp. ImageOptim works only within the source format — it does not transcode. Similarly, if your workflow is already automated through a Node.js build pipeline using sharp or imagemin, the desktop app adds little beyond convenience.
How does ImageOptim compare to alternatives?
The closest Mac-native competitors are Squash and JPEGmini. Squash offers a polished UI and WebP export but costs money. JPEGmini is JPEG-only and similarly paid. For command-line users, tools like pngquant, oxipng, and MozJPEG do everything ImageOptim orchestrates — but require scripting glue to chain them together. ImageOptim is the rare case where the free option is also the most convenient: it bundles the best open-source codecs, surfaces them through drag-and-drop, and gets out of your way.
Against cloud services like TinyPNG or Kraken.io, ImageOptim wins on privacy (files never leave your machine) and on batch processing speed for large local catalogs. The trade-off is no WebP or AVIF output — the cloud services tend to be ahead on modern format support.
