Today, ImgZilla 1.3 is officially available on the Mac App Store.
Its core function is clear: compress images on your Mac in place—file name, path, and format remain unchanged, and the original goes to the Trash by default so you can restore it anytime.
All of this happens on your own Mac, with no network connection required. Images never leave your computer and are never uploaded to any server—privacy and data security have been fundamental from the start.
This functionality looks simple, but we tested, scrapped, and rebuilt it many times. This article isn't about “what features we built”; it's about the specific problems we encountered in real-world usage and the final form they took.
The Words “In-Place Overwrite” Demand Utmost Care
Most image compression tools save the result as photo-min.jpg—safe, but they leave the hassle to you: the file name changes, and references in product listings, paths in web templates, and ordering in archive directories all have to be updated.
ImgZilla takes a different path: the compressed result is written directly back to the original path, original file name, and original format. A JPG remains a JPG, and references don't need to change.
The cost is: this tool touches users' original files. If any step goes wrong, what's lost isn't cache—it's a full day of photos someone took, or years of collected archives.
So the real effort has never been the compression itself—that's handled by mature encoders—but the protective measures around “what if.” The improvements below all came from real issues found during testing.
Things Changed During Testing
1. The Original File Protection Strategy Was Redone Once
The initial design copied the original to a dedicated backup directory. The logic was fine, but it was awkward to use: the backup directory would quietly grow, and users wouldn't discover a full extra copy on their disk until months later, when what they originally wanted was to save space.
The current approach is Trash first: when compression succeeds, the original is moved to the system Trash, then the compressed result is written back to the original path.
Restoring is now something every Mac user already knows: open the Trash, right-click, and choose “Put Back.” No new concepts to learn, and no hidden directory that keeps growing. This option is enabled by default in Settings; turning it off means direct overwrite without recovery, so a confirmation dialog appears when you disable it.
2. That Dialog on External Drives Was Forced Out by Testing
When testing on portable drives, NAS, and network volumes, we hit a common macOS issue: these locations often cannot move files to the Trash.
The first version's handling was to throw an error and skip—resulting in users dragging in an entire folder and nothing happening.
Now the handling is: compression pauses, and a dialog lets you decide:
- Choose a backup directory: the original is copied there, then overwritten;
- Skip backup: after a second confirmation, it overwrites directly without keeping a copy;
- Close the dialog: treated as cancel, and the entire task stops.
Another detail added during testing: your choice applies to all remaining files in this batch; otherwise 500 images would trigger 500 dialogs—that's how the first version was, and using it once was enough to be unbearable.
The selected backup directory is recorded as the default backup location (subdirectories are created by time under
~/Library/Application Support/ImgZilla Backups/) and is used preferentially for similar situations later.
3. “Already Minimized”: Better to Do Nothing
Some images have already been compressed before being dragged in (whether by other tools or by ImgZilla previously), and re-compressing usually only yields a fraction of a percent in size change. We set a hard rule: if the compression ratio is less than 0.4%, leave it alone, mark it as “Already Minimized” in the list, keep the original file as is, and don't consume free quota.
This rule makes the statistics less impressive—drag in a whole album of already-compressed images and most might show “Already Minimized.” But we believe a tool that re-compresses your images just to show off results doesn't deserve to touch your original files.
4. When File Extensions Lie
In test samples, we saw many files with .png extensions that were actually JPEG—images passed around through various channels, more common than expected.
Now ImgZilla reads the magic bytes in the file header to determine the real format and chooses the encoder accordingly. Even if the extension is wrong, it handles the file correctly.
5. Serial Processing, Not Parallel
Compressing one by one in sequence may seem “not fast enough.” We tried parallel processing; it was indeed faster, but when errors occurred in large batch tasks, the state became hard to track—and this tool is overwriting users' original files.
Stability takes priority over peak speed, so we kept serial processing. To clarify, serial refers to processing tasks one by one, while the compression of each image itself uses multithreading inside the encoder, so it doesn't waste the CPU's multi-core capability. As compensation in the UI, we did the following: the current item automatically scrolls into view, auto-scroll pauses on mouse hover, the bottom shows real-time counts of processed images and saved space, and a system notification is sent when all is done.
6. When Free Quota Runs Out, the Task “Pauses,” Not “Aborts”
The free version can compress 10 images per day, resetting automatically at the next day. During testing we found that the moment of interruption makes a huge difference in experience: if you drag in 200 images and it fails and exits at the 10th, users have to re-add all files—then the prompt becomes pure harassment.
Now the behavior is: when quota runs out, the task pauses in place and shows a purchase panel; after purchase, it continues from where it left off without re-adding any files. Also, quota is only deducted on successful compression—failed compressions or “Already Minimized” don't count.
7. 19 Language Options, and a Less Obvious Finishing Touch
The interface fully supports 19 language options (including “Follow System,” Simplified and Traditional Chinese, English, 日本語, 한국어, major European languages, العربية, Tiếng Việt, and more), switchable anytime in Settings, taking effect immediately, no restart required.
This part of the work far exceeded expectations and was one reason the release was pushed back. But for a tool on the global App Store, letting users see their own language is the most basic respect.
About Image Quality: Don't Believe Us, See for Yourself
Compression is hardest to build trust in. So let's be clear:
- PNG (oxipng) and SVG (svgcleaner) are truly lossless compression, pixels unchanged;
- JPEG, WebP, AVIF, HEIC/HEIF, and GIF are lossy re-encoding in principle, but the parameters are chosen in the visually lossless range—almost indistinguishable to the naked eye, but it is not “lossless,” and we won't mix those two terms.
Moreover, you don't have to accept this on trust. ImgZilla has a built-in image comparison window (⌘D): left is before compression, right is after; drag the divider in the middle to compare side by side, zoom to actual size, and scrutinize details. Every successfully compressed image in the list can open the comparison with one click.
If you're not satisfied, go to the Trash and put the original back. That fallback is always there.
Parameters are fixed, with no quality slider in the UI. This is a deliberate trade-off: tuning requires understanding quantization tables, encoding method, speed, and other technical concepts—get it wrong and you either waste effort or blur the image. We've done that for you—parameters for each format are individually tuned. Drag in, click compress, and you get the ideal balance point for that format under current parameters.
If you're used to adjusting compression parameters yourself, we still suggest trying ImgZilla first—the parameters have already been tuned and may save you the effort of trial and error.
What It Doesn't Do
Equally important boundaries, written here to save you from discovering after download:
- macOS only (12.3 or later). No Windows version, no iOS version, no web version.
- No format conversion. A JPG remains a JPG; it won't become WebP.
- No resizing. No resolution changes, no cropping.
- No guarantee of size reduction. Already-optimized images may not compress at all; they'll be honestly marked as “Already Minimized.”
- EXIF is removed by default (including GPS location, making files smaller and more privacy-protective). If you need to keep shooting parameters, copyright, and color profiles, go to Settings and manually enable “Preserve EXIF Information”.
There's one more thing worth emphasizing: all compression happens locally on your Mac. Apart from App Store purchase verification, ImgZilla needs no internet connection, and images never leave your computer—no queue, no image count limit, and no “upload to someone else's server.” The encoders are all local static libraries bundled inside the app.
Ready to Use Now
- Free version: 10 images per day, resets automatically the next day, no feature restrictions.
- Unlock limits: one-time purchase (unlimited) or monthly subscription, priced according to your App Store region. If you change computers or reinstall, just click “Restore Purchase.”
Suggested first use: drag in an image you don't care much about, compress it, click “Compare,” and see the quality for yourself before deciding whether to hand over an entire folder.
That's also how we hope this tool is used—verify first, then trust.
If you have any questions or suggestions, feel free to tell us via the menu “Help → Feedback.” 1.3 is a version you can use with confidence, but it certainly won't be the last.
ImgZilla 1.3 is now available on the Mac App Store. Requires macOS 12.3 or later.