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How to Reduce File Size on a Mac: Every File Type
Yes, you can reduce file size on a Mac, but the method depends on the file type. Photos, PDFs, video and audio each need to be re-encoded at a lower quality. Zipping barely shrinks them. Start with the file type below.
How do I make a file smaller on a Mac?
Find the file type first. Smaller files come from one of two things: throwing away detail you will not miss (lossy compression), or storing the same data more efficiently (lossless). Photos, video and audio are already compressed, so you must accept some loss. Text and documents are the opposite: they shrink a lot with no loss at all.
| File type | Free built-in route | Where it falls short |
|---|---|---|
| Photos (JPG, HEIC, PNG) | Preview > Tools > Adjust Size, or Export with the Quality slider (JPEG, HEIC) | One file at a time; no quality slider for PNG |
| Preview > File > Export > Quartz Filter > Reduce File Size | Often overshoots and blurs text and images | |
| Video | QuickTime Player > File > Export As (resolution only) | Cuts resolution, with no control over bitrate |
| Audio | Music app > File > Convert, or afconvert in Terminal | Fiddly for batches |
| Folders of text, documents | Finder > right-click > Compress (zip) | Does almost nothing for photos or video |
How do I reduce the size of photos on a Mac?
Open the photo in Preview, choose Tools > Adjust Size, and lower the pixel width. Pixels matter more than anything else: a 4,000 px photo shown at 1,200 px wastes most of its bytes. For JPEG, File > Export also has a Quality slider.
In Terminal, sips does the same without opening anything. See the sips command guide for batches. The comparison of image compression methods on Mac covers the trade-offs in detail.
sips -Z 1600 photo.jpg --out photo_small.jpgHow do I reduce the size of a PDF?
Open the PDF in Preview and use File > Export, then pick Reduce File Size from the Quartz Filter menu. It is quick and it is blunt. Many people find the result too blurry, so check it before you send it. For control over how hard it squeezes, read how to compress a PDF on a Mac. A PDF made from text and vector art is already small. Scans and image-heavy PDFs are where the savings are.
How do I reduce the size of a video?
In QuickTime Player, choose File > Export As and pick a lower resolution such as 1080p or 720p. That is the only lever QuickTime gives you. For a real size cut, you need a more efficient codec (H.265 instead of H.264) and a lower bitrate. In our test, a generated 8-second 720p H.264 clip of 3.2 MB re-encoded to H.265 at CRF 28 came out at 2.1 MB. That clip is synthetic, so your own footage will differ.
More in how to compress a video on a Mac and H.265 vs H.264.
How do I reduce the size of an audio file?
Lower the bitrate or switch from WAV or AIFF to AAC or MP3. WAV stores audio uncompressed, so converting is the single biggest win. The audio bitrate guide shows what each setting sounds like, and compressing audio on a Mac has the steps.
Does zipping a file reduce its size?
Only if the content is not already compressed. We zipped five synthetic JPEGs (5,368,893 bytes) with Finder’s own method and got a 5,369,373 byte archive, slightly bigger. Five plain text files went from 157,295 to 13,391 bytes. Zip is for bundling and for text, not for photos, video or most PDFs.
When is Smol the wrong tool for this?
For one photo, one PDF or one clip, Preview, QuickTime and sips are free and enough. Do not buy anything for a one-off.
Smol earns its $29 when the job repeats or the folder is mixed. You drag in photos, PDFs, video and audio together, or right-click in Finder, and every file is compressed on your Mac with nothing uploaded. By default it writes a copy with a _compressed suffix and keeps the original. On the generated 3000 x 2000 JPEG in our test, a default Smol compress took 1,040,309 bytes down to 151,330. Smol resizes images to fit 2000 x 2000 px by default, which accounts for some of that, and the fixture is synthetic. See pricing, or compare the best image compressors for Mac.
How we checked this
Zipped generated JPEG and text fixtures with ditto on macOS 27.0.1, re-encoded a generated MP4 with H.265 CRF 28, and ran one default Smol 1.0.35 compress. Menu paths are the standard Preview and QuickTime ones. 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.
Reducing file size on a Mac: common questions
Can you reduce file size on a Mac without losing quality?
Only for some files. Text, documents and folders of uncompressed data shrink with no loss through zip. Photos, video and audio are already compressed, so a smaller file means lower quality. The loss is often invisible if you lower pixel dimensions or bitrate sensibly, rather than pushing quality to its minimum.
What is the fastest way to make a file smaller on a Mac?
For a photo, Preview > Tools > Adjust Size. For a PDF, Preview > File > Export > Quartz Filter > Reduce File Size. For video, QuickTime Player > File > Export As at a lower resolution. Each takes under a minute for a single file. For many files at once, use a batch tool.
Why will a zipped photo folder not get smaller?
JPEG, HEIC, MP4 and most PDFs are already compressed. Zip finds no repeated patterns left to remove, so the archive ends up the same size or slightly bigger. In our test, five JPEGs totaling 5,368,893 bytes zipped to 5,369,373 bytes. Zip helps only with uncompressed content such as text, WAV audio or raw data.
How do I compress files on a Mac to email them?
Shrink each file for its type first, then attach. Many mail providers cap attachments around 20 to 25 MB. If the files are still too big, Apple Mail can send them through Mail Drop, which handles larger attachments. See the Mail Drop guide on this site for its limits.
Does a smaller file always mean lower quality?
No. Much of a typical file is waste: oversized pixel dimensions, extra metadata, or a bitrate higher than anyone can hear. Removing that costs nothing visible. Quality drops only when you cut past the point where detail is actually visible, so check the result before you delete the original.
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