Comparison
Smol vs ImageOptim: Which Mac Image Compressor in 2026
Smol vs ImageOptim comes down to format: pick ImageOptim for free JPEG, PNG, GIF and SVG work; pick Smol for AVIF or WebP output, or one app for images, PDFs, video and audio. For JPEG in and JPEG out the two produced files of about the same size in our benchmark, and ImageOptim is free and faster.
We make Smol, so read this as a head-to-head from one of the two sides. The numbers come from our published benchmark of 24 photographs, and the ranking rests on that test, each tool’s documented capabilities, and price. ImageOptim is first because, for many readers, free and good enough is the right answer.
| Tool | Best for | Price | Local or upload |
|---|---|---|---|
| ImageOptim | Free JPEG, PNG, GIF and SVG optimization | Free | Local app |
| Smol | AVIF and WebP output; images, PDFs, video and audio in one app | $29 once | Local app |
If you want the shorter pitch for leaving ImageOptim, that lives on the ImageOptim alternative page. This page is the fuller, fairer head-to-head.
ImageOptim
Free, open source, and fast at the job it does.
ImageOptim is a free, open-source Mac app. Per its own page, it handles JPEG, PNG, SVG and animated GIF, requires macOS 11 or later, and takes files dragged into its window, dropped on the Dock icon, sent from the Finder Services menu, or run from the command line. EXIF data, including GPS location and camera serial numbers, is removed by default, and you can turn that off in Preferences.
Out of the box it is lossless: the pixels stay identical and only the file wrapper shrinks. On our 24 photographs that saved 8.9% on the JPEGs and 4.3% on the PNGs, which is what lossless work can do for photos. Its lossy mode is off by default; switch it on in Preferences and the same JPEGs came out 63.8% smaller.
Where it wins: price, speed on JPEG (about 8 times faster than Smol in our run), and the only option here that can change no pixels at all. Where it stops: the output formats are the input formats, so it cannot write AVIF or WebP. Our roundup also notes that its lossy mode rewrites files in place and moves the originals to the Trash. Pick it if you ship JPEGs and PNGs and never need another format.
Smol
A paid Mac app that adds AVIF and WebP, and covers PDF, video and audio too.
Smol compresses and converts images, PDFs, video and audio on your own Mac. Nothing is uploaded and there is no account. Images can be written as JPG, PNG, WebP, AVIF, HEIC or GIF, with a quality setting from 0 to 100 (default 75). It takes whole folders, mixed file types in one batch, and offers presets, a Finder Quick Action, clipboard compression and watched folders. It needs macOS 13 or later on Apple Silicon, or macOS 14 or later on Intel.
The image result that matters here: compressed from the same JPEGs and matched on the same quality score, Smol’s AVIF files needed 20 to 22% fewer bytes than ImageOptim’s lossy JPEGs. JPEG to JPEG was a tie. At its defaults it made the 24 JPEG photos 69.3% smaller. Those are small, 768 by 512 film photographs, so treat them as a direction, not a promise for your camera files.
Limits, plainly: it is not free, there is no free trial and purchases are not refundable. It has no lossless mode, always re-encodes, and is slower than ImageOptim on JPEG. By default it resizes to fit inside 2000 by 2000 px and strips metadata, so photographers should change the resize setting. Pick it if you want AVIF or WebP, or if images are one of several file types you handle.
Smol vs ImageOptim: how do they compare on size and quality?
JPEG to JPEG is a tie, and AVIF is where Smol pulls ahead: at the same quality score its AVIF needed 20 to 22% fewer bytes than ImageOptim’s lossy JPEG.
All figures come from the 9 October 2026 run on the benchmark page: 24 small Kodak photographs, ImageOptim 1.9.3, Smol 1.0.35, Apple M2 Pro. Sizes were matched on the SSIMULACRA2 score, not on a quality slider number, because the sliders mean different things in different tools.
| Input to output | Result at a matched score |
|---|---|
| JPEG to JPEG | Level. ImageOptim lossy and Smol JPEG landed at about the same size |
| JPEG to AVIF (Smol only) | 20 to 22% fewer bytes than ImageOptim's JPEG |
| PNG to AVIF (Smol only) | 71 to 76% fewer bytes than ImageOptim's lossy PNG |
| PNG to PNG | Close: the widest gap at any matched score was 0.5% |
A different measurement shows the same picture. Lossless, ImageOptim saved 8.9% on the JPEGs and 4.3% on the PNGs; Smol’s defaults saved 69.3% and 69.2%. The catch is that Smol’s saving is lossy and ImageOptim’s default is not, so these two are not a like-for-like comparison. That is why the matched-score table above is the one to trust.
Which is faster, Smol or ImageOptim?
ImageOptim is faster on JPEG, and Smol was faster on PNG. In our run ImageOptim at its defaults took about 0.9 seconds for the 24 JPEGs against about 7.1 for Smol.
On PNG the order flipped. ImageOptim’s lossy PNG mode took about 17 seconds, while Smol produced a PNG of matching size and score in about 10.4 seconds, roughly 1.6 times faster. Smol’s PNG to AVIF took about 8.7 seconds. Neither is slow for a folder of photos; speed matters mostly if you run thousands of files.
How do I compress images on a Mac for free?
Use ImageOptim for lossless JPEG and PNG work, or Preview for a single photo. Both are free and neither uploads anything.
- Open the photo in Preview.
- Choose File > Export.
- Pick JPEG or HEIC as the format and drag the Quality slider down.
- Watch the file size shown under the slider, then click Save.
For a whole folder with no format change, drag it into ImageOptim. For shell loops, see our sips guide, and for every method side by side, the methods comparison.
Is ImageOptim lossless or lossy?
Lossless by default, with an optional lossy mode in Preferences. In lossless mode the decoded pixels do not change, which is the one thing Smol cannot offer, since it always re-encodes.
That makes ImageOptim the right tool for archives, UI assets and anything that goes through further editing. If you only ever need to shrink a final delivery copy, lossy output is fine and the format matters more than the optimizer. ImageOptim also lists a separate web service and API on its site, for servers rather than the Mac app.
How we chose and ranked
We make Smol. We ranked on measured results from the 9 October 2026 benchmark, documented capabilities, price, and whether files stay on your Mac. ImageOptim details were checked against its own site on 14 October 2026, and no new test was run for this page.
Only two tools are listed because this is a head-to-head. For more options, see the best image compressor for Mac roundup, or the Smol vs TinyPNG comparison if you are weighing an online tool.
Frequently asked questions
Smol vs ImageOptim: which one is better?
It depends on the output you want. For JPEG to JPEG the two were level in our test, and ImageOptim is free and faster. Smol writes AVIF and WebP, which ImageOptim cannot, and its AVIF needed 20 to 22% fewer bytes than ImageOptim's JPEG at the same quality score. We make Smol, and the test used 24 small photographs.
Can ImageOptim convert to AVIF or WebP?
No. ImageOptim optimizes JPEG, PNG, SVG and animated GIF files and keeps each in its own format, according to its own website. To produce AVIF or WebP on a Mac you need another tool, such as Smol, which writes both. The built-in sips command can also write HEIC or AVIF without a download.
Is ImageOptim really free?
Yes. Its website describes it as free to download and open source under the GPL v2 or later, with optional donations. Smol is the opposite: a $29 one-time purchase for one Mac, with no free trial and no refunds. If you only need JPEG and PNG optimization, ImageOptim costs nothing.
Does Smol have a lossless mode like ImageOptim?
No. Smol always re-encodes images, so it cannot promise pixel-identical output. Metadata stripping is a separate operation that does not re-encode. For lossless optimization of PNG or JPEG files, ImageOptim is the better fit and is free. Smol suits cases where smaller lossy files, or a new format, are the goal.
Does either app upload my images?
Smol runs entirely on your Mac with no upload, no account and no server. ImageOptim is a Mac app that works on files you drop into it, and its site separately lists a web service and API for server use. If upload matters to you, check which of the two you are using.
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