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Zip vs Compress on Mac: Why Zipping Photos Barely Helps
To compress a folder on a Mac, right-click it in Finder and choose Compress. That makes a zip file. But zipping photos, video and most PDFs barely shrinks them, because they are already compressed. Zip is lossless and reversible. Real size cuts need re-encoding.
How do I compress a folder on a Mac?
Control-click (or right-click) the folder or files in Finder and choose Compress. Finder writes Archive.zip for several items, or FolderName.zip for one. Double-click a zip to unpack it. The same job from Terminal:
zip -r photos.zip photos/
# or the Finder-style archive that keeps Mac metadata
ditto -c -k --sequesterRsrc --keepParent photos photos.zipZip needs no extra software on a Mac or Windows PC, which is why it is the default for sending a bundle of files. That is its real job: one file instead of fifty. It is not a size tool for media.
Does zipping reduce file size?
Only when the data has patterns left to squeeze. Zip is lossless: it finds repeated data and stores it more compactly, and unzipping returns every byte. JPEG, HEIC, MP4 and AAC files have already had their repeated data removed, so there is almost nothing left. Here is what we measured on generated test files.
| Fixture | Original (bytes) | Zipped (bytes) | Change |
|---|---|---|---|
| 5 JPEG photos, 3000 x 2000 | 5,368,893 | 5,369,373 | Slightly larger |
| 8 s 720p H.264 MP4 | 3,213,330 | 3,208,756 | About 0.1% smaller |
| 5 plain text files | 157,295 | 13,391 | About 91% smaller |
| 10 s WAV (sine tone) | 882,078 | 10,324 | Almost nothing left |
The JPEGs are synthetic and noisy, so they are close to the worst case for zip. Real photos behave much the same, since a JPEG is already entropy-coded. The WAV is a pure tone, so it shrinks unrealistically well. Real recorded WAV files compress far less. Treat the text row as the typical win and the JPEG and MP4 rows as the typical disappointment.
How do I zip images on a Mac and make them smaller?
Zip them for sending, but shrink them first. To make an image smaller you must re-encode it: lower the pixel dimensions, lower the quality, or switch to a more efficient format. Preview does this one image at a time (Tools > Adjust Size). sips does it in a loop. Our guides cover both: reducing file size in Preview, the sips command and every image compression method compared.
# resize every JPEG in a folder so the long edge is 1600 px
mkdir -p small && for f in photos/*.jpg; do sips -Z 1600 "$f" --out "small/$(basename "$f")"; done
zip -r small.zip small/When is zip the right choice?
- You need to send many files as one attachment and want them untouched, bit for bit.
- The files are text, source code, logs, CSV or other uncompressed data.
- You need to preserve folder structure and file dates.
- The recipient must get the exact originals, such as a print vendor or an archive.
Zip is the wrong choice when the goal is a smaller photo, video or PDF. A zip of videos is still the size of the videos, and the recipient still has to unzip it first. See how to compress a video on a Mac and how to compress a PDF for the real route.
When is Smol the wrong tool for this?
If you only need to bundle files or shrink text, Finder’s Compress is free and enough. For a single photo, Preview and sips are enough too. Smol does not make archives.
Smol earns its $29 when you have a folder of photos, PDFs, video and audio that you need smaller, not just bundled. Drop the whole folder in, or right-click in Finder, and each file is re-encoded on your Mac with nothing uploaded. It writes a copy beside the original with a _compressed suffix by default. On one generated 3000 x 2000 JPEG, a default Smol compress went from 1,040,309 to 151,330 bytes, partly because Smol fits images inside 2000 x 2000 px by default. Smol has no lossless image mode, so it is not for pixel-identical copies. Details at pricing. Then zip the smaller folder if you want one attachment.
How we checked this
Zipped generated fixtures with ditto and the zip command on macOS 27.0.1 and compared byte counts with stat. One default Smol 1.0.35 compress on a generated JPEG. Fixtures are synthetic. Facts last checked . We make Smol, so treat our claims about it with the same care as any vendor’s, and see our editorial policy.
Zip vs compress on Mac: common questions
Is zipping the same as compressing on a Mac?
Finder calls zipping "Compress", so the menu item is the same word, but the effect differs. Zip is lossless bundling that shrinks only uncompressed data like text. Compressing media means re-encoding it at lower quality or resolution, which removes detail. Zip changes nothing about the files inside, and unzipping restores them exactly.
Why did my zip file come out larger than the folder?
The files were already compressed, so zip found no patterns to remove, and the archive added its own headers and file index. We saw this with five JPEGs: 5,368,893 bytes became 5,369,373. The difference is tiny, but it shows zip cannot shrink photos.
Does zipping reduce photo quality?
No. Zip is lossless, so the photos inside are byte-for-byte identical after you unzip them. The flip side is that it cannot shrink them much. If you want smaller photos you must accept re-encoding, which does reduce quality slightly, or reduce dimensions.
How do I compress a folder on a Mac to email it?
Right-click the folder in Finder and choose Compress, then attach the zip. If the zip is over your provider limit, shrink the photos or video inside first, because zip will not do it. For very large files, Apple Mail can send through Mail Drop instead of attaching them.
Is the Finder zip the same as a 7z or RAR?
No. Zip is the format Finder creates and opens natively. 7z and RAR need extra software to open, and like zip they gain little on photos or video. For media, a different archive format is not the fix.
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