Your photos are bigger than they need to be.
JPEGPack finds, photo by photo, the smallest file that still looks identical, at the same resolution with the same pixels. Sometimes it is 30% less, sometimes 80: each photo’s exact number.
macOS 13 or later · Apple SiliconWhat nobody taught you about exporting.
The "quality 90" myth
The slider in Lightroom and Photoshop is one fixed number for every photo — and it does not measure what the eye sees. On a hard photo it does damage; on an easy one it wastes megabytes. Each photo needs a different point.
Pixels are not bytes
Delivering at full resolution does not force a heavy file. Resolution is how many pixels a photo has; weight is how they are stored in the file. JPEGPack does not remove a single pixel — it reorganizes how they are stored.
And the bill keeps growing
Cameras with ever more megapixels, drives and cloud plans that fill up fast, clients complaining about heavy links. The extra weight does not just sit on disk: it charges you on every delivery.
Check with your own eyes.
Real pairs, untouched: the original file and the compressed one, with measured sizes and a 100% crop. Drag the divider — and download both files to run the Photoshop test.
Outdoor portrait−80%
Smooth skin and a blurred background: the easy case. The ruler allows a big squeeze without touching what the eye sees.
before · 17.03 MBafter · 3.44 MBWedding dress · lace−74%
Lace and fabric are fine texture, where careless compression smears first. Here it stays intact.
before · 8.98 MBafter · 2.30 MBSea at sunset−84%
A sunset gradient is where a bad compressor creates banding in the sky. Drag the bar and look for it.
before · 7.19 MBafter · 1.13 MBFox · fine fur−23%
Fine fur, strand by strand: one of the hardest cases. The app squeezes only as far as the ruler allows.
before · 5.12 MBafter · 3.91 MBConcert crowd−40%
Thousands of tiny faces and stage light: a hard photo, a moderate squeeze, on purpose.
before · 5.75 MBafter · 3.45 MBHong Kong · windows−68%
Thousands of windows and straight lines. Edge sharpness is the first thing to go: check the crop.
before · 9.52 MBafter · 3.07 MBParis · fountain−73%
Stone, water frozen mid-air and fine architectural detail.
before · 18.28 MBafter · 4.87 MBForest−75%
Dense foliage is chaotic detail everywhere. And still the squeeze is big.
before · 22.82 MBafter · 5.59 MBMountain sunrise−62%
A sunrise sky and detailed rock in one photo: two challenges, one exact number.
before · 24.01 MBafter · 9.10 MBYosemite−75%
The classic landscape: granite, forest and sky.
before · 16.19 MBafter · 4.06 MBKid with a camera−71%
Vintage-camera detail and skin in the same frame. The app finds the right point without sacrificing either.
before · 8.95 MBafter · 2.59 MBPhoto by photo, until it finds the exact number.
JPEGPack never uses one fixed number for every photo. It analyses each one and searches for that photo’s exact point: the smallest file that still passes a ruler of what the eye sees.
A ruler of what the eye sees.
To decide, the app uses SSIMULACRA2 — a ruler built to measure what the human eye perceives, not how many bytes changed. It compares the compressed photo against the original and returns a score. Only results scoring 82 or higher pass: the level at which the difference stops being visible.
The two open identically on screen, side by side. The difference is in the size — and in the score, which guarantees the savings did not come out of the quality. It is not one fixed guess for every photo: it is this photo’s exact number.
Compress, measure, adjust — until that photo’s exact number.
There is no single right number for every photo — there is the right number for each one. JPEGPack compresses at a candidate quality, measures it on the ruler, squeezes or eases off, and repeats until it finds the smallest file that still looks identical.
Compress
The photo is re-encoded with mozjpeg at a candidate quality.
Measure
The compressed version is compared against the original on the eye’s ruler.
Adjust
Score to spare? Squeeze harder. Below 82? Ease off.
Repeat
The search converges on the smallest file that still passes the ruler.
Write
One final pass at full resolution. EXIF, XMP, ICC and file dates stay intact.
The search runs on a sample. The final encode is a single pass.
Measuring several attempts at full resolution would be slow. The search samples four patches spread across the photo and keeps the score of the WORST one — because compression damage does not show up where detail is densest, but in smooth gradients, which a single crop would miss. Only the final encode touches full resolution, in a single pass. In practice: about 10 seconds for 30 13.5-megapixel photos on Apple Silicon. And the queue takes real-world volume: thousands of photos in one batch — a graduation delivery with over 100,000 photos runs through in an afternoon, unattended.
The re-encode uses mozjpeg, an encoder that squeezes more compression out of the same JPEG format. The file that comes out is still an ordinary JPEG: it opens in any browser, gallery and editor, with no plugin and no conversion.
The Photoshop test.
Before trusting the app, we ran the hardest test we know. It still stands — and it is worth more done by you than told by us.
Stack
Open the before and the after in Photoshop, as layers, one exactly on top of the other.
Zoom
Zoom to 100%. Go to the face, the hair, the sky — where bad compression shows first.
Toggle
Switch the top layer on and off. Try to spot the difference.
You can’t. And you don’t have to take this sentence on faith: the 15-day trial exists so you can repeat the experiment with your own photos, on your own monitor.
Where the weight hurts your work.
Delivery
The gallery opens fast and the client downloads without complaining about the link. The same photos, at the same resolution — only the weight changed.
Storage
At 30 to 80% less space per photo, depending on the case, the same drive and the same cloud plan hold up to twice as many jobs, or more.
Backup
Backup charges you in time and in gigabytes, and the maths is linear: 40% fewer bytes is 40% less upload and 40% less cost per GB.
Archive
Old jobs shrink in copy mode, without touching the originals: the compact versions go to another folder, and the source stays as it was.
Three doors, one engine.
In Lightroom
Add “JPEGPack - Otimizar JPEG” under Post-Processing and photos come out optimized as part of the export itself. It adds to the preset you already use: folder, naming, watermark and metadata stay exactly as they are. Included in the licence.
In the Finder
Right-click photos or folders and choose to optimize the originals or export a copy at the size you configured. No app to open, nothing to drag.
In the app
Drag the whole folder onto the window. This is the path for big batches, with the built-in file browser and the before-and-after result on screen.
One fixed number, and the exact one.
One-off purchase, no subscription.
One licence for up to two Macs. You pay once and keep using the app even after the year of updates ends.
- Permanent licence, never expires
- Use on up to 2 Macs
- 1 year of updates included
- The app keeps working after the first year
Download it, use it — and run the Photoshop test on your own photos before deciding.
- The full app, with no feature limits
- No credit card
- No account and no email
Questions.
Does this ruin my photos?
How many photos can I compress at once?
Isn’t "visually lossless" just marketing?
Does the resolution go down?
How much smaller does a photo get?
Do I have to open the app to compress?
How does the Lightroom plug-in work?
What about metadata? EXIF, colour, dates?
Does it touch my originals?
Is it fast?
Does it work with RAW, PNG or HEIC?
Does it run on Intel?
Deliver the same photos. Upload fewer bytes.
Download JPEGPack and let your next job weigh what it actually needs to.
Download for MacmacOS 13 or later · Apple Silicon · version 1.2.3 · 7,1 MB