Images
How to Make a JPEG Smaller on a Mac
Open the JPEG in Preview, choose Tools > Adjust Size, drop the width (try 2000 pixels), then File > Export and slide Quality down. Resizing does most of the work. Lowering quality alone saves far less.
A JPEG has two things you can shrink: how many pixels it holds and how hard those pixels are compressed. This guide shows both, with sizes we measured.
How do I make a JPEG smaller in Preview?
Preview is already on your Mac and handles one file at a time.
- Open the JPEG in Preview.
- Choose Tools > Adjust Size…
- Set Fit into to a custom size, or type a new Width. Keep Scale proportionally ticked. Resample image must stay on.
- Click OK, then File > Export…
- Pick JPEG as the format and drag the Quality slider left. The dialog shows the estimated file size as you move it.
- Save under a new name so the original stays.
The estimate in the Export dialog is the useful part. Keep sliding until the size is where you need it, then stop. Below roughly the middle of the slider, blocky patches show up in skies and skin.
Is it better to lower the quality or the pixel size?
Lower the pixel size first. A phone photo is 4,000 pixels wide or more, and almost nobody views it that large. Halving the width removes three quarters of the pixels. Lowering quality only makes each pixel cheaper to store.
We tested this on one 4032 × 3024 JPEG (2.73 MB) using the sips command. The file is a synthetic test image, so treat the ratios as a guide and expect different numbers on your own photos.
| Change to the 2.73 MB original | Resulting size |
|---|---|
| Same pixels, sips quality 70 | 1.79 MB |
| Same pixels, sips quality 50 | 0.88 MB |
| Resized to 2000 px on the long edge, default quality | 0.37 MB |
| Resized to 1600 px on the long edge, quality 70 | 0.24 MB |
The resized file at quality 70 is about a quarter the size of the full-pixel file at quality 50, and it will look cleaner on a normal screen because the compression is gentler per pixel. Quality 50 on all 12 million pixels is the worst of both.
How do I make a JPEG smaller from Terminal?
The built-in sips tool needs no install. Resize so the long edge is at most 2000 pixels, or set a quality, or both. Always write to a new file with --out.
sips -Z 2000 photo.jpg --out photo-small.jpg
sips -s format jpeg -s formatOptions 70 photo.jpg --out photo-q70.jpg
sips -Z 1600 -s format jpeg -s formatOptions 70 photo.jpg --out photo-web.jpgOne quirk from our test: sips quality numbers do not match other tools. Asking sips for 85 on a file saved at 95 in another tool gave a file the same size, not a smaller one. Judge by the output size, not the number.
What size should a JPEG be for email, the web or a form?
Pick the destination, then work backward from its pixel width. Screens rarely show more than about 2000 pixels of width for a photo in a page. Many upload forms and email services care about the file size in megabytes instead, so check the stated limit first.
- Sending photos in Mail: see reducing photo size for email on a Mac.
- Posting on a website: keep the width at what the layout shows, and read image optimization for Core Web Vitals.
- Upload form with a megabyte cap: resize to 2000 px, export, and check the size. Repeat at a lower width if it is still over.
Will making a JPEG smaller ruin it?
Each save at lower quality throws away detail you cannot get back. JPEG is lossy, so re-exporting a copy again and again stacks the damage. Always work from the original and save a copy. Resizing discards pixels permanently too, so never shrink the only copy of a photo you may want to print.
A few cheap habits keep quality high: resize once, export once, and keep the original in its folder. If a file has to stay pixel-identical, a lossless optimizer is the answer instead, and it saves much less. Our Smol vs ImageOptim comparison covers that trade.
When is Smol the wrong tool for this?
For one photo, Preview or sips is enough, and both are free and already on your Mac. Use them. Smol is slower than a sips loop on small files, and it has no lossless mode, so it will not give you a pixel-identical smaller JPEG.
Smol earns its $29 (once, one Mac) when you have a folder, not a file. Drop a mix of JPEGs, PNGs and HEIC files in and each gets a smaller copy beside the original with a _compressed suffix. You can also right-click in Finder, and nothing is uploaded anywhere. By default Smol resizes images to fit inside 2000 × 2000 pixels and strips metadata, which suits web and email but not print. On the 24 small test photos in our benchmark, JPEG at quality 75 came out 69.3% smaller. Those are small 768 × 512 film scans, so your camera files will differ. See the best image compressor for Mac roundup, or buy Smol.
How we checked this
Generated one 4032 x 3024 test JPEG and measured sips resizes and quality settings on an Apple Silicon Mac. Preview steps are standard menu paths; Smol facts come from the product fact sheet and benchmark. 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.
Making JPEGs smaller: common questions
How do I reduce a JPEG to a specific size in MB on a Mac?
Use Preview. Open the file, choose File > Export, set the format to JPEG and move the Quality slider while watching the estimated size in the dialog. If it will not reach your target, shrink the width first with Tools > Adjust Size, then export again. Save a copy each time.
Does resizing a JPEG reduce its file size?
Yes, and usually more than lowering quality. Fewer pixels means less data to store. In our test, resizing a 2.73 MB, 4032-pixel-wide file to 2000 pixels gave 0.37 MB at default quality, while keeping every pixel at quality 50 still left 0.88 MB.
Can I make a JPEG smaller without losing quality?
Not strictly. A smaller JPEG always discards something, either pixels or detail. A lossless optimizer can trim a few percent without changing the picture, but it saves far less. Smol always re-encodes, so it is not lossless either. Resize to the size you will actually display and keep the original.
What is the difference between making a JPEG smaller and converting it?
Making it smaller keeps the JPEG format and changes pixels or quality. Converting changes the format, for example to WebP or AVIF, which are often smaller at similar quality but not accepted everywhere. If a form demands JPG, stay with JPEG and resize.
Why did my JPEG get bigger after I exported it?
Preview or another app saved it at a higher quality setting than the original had, or kept the same pixels at near-maximum quality. Lower the quality slider, or resize. Always compare the new size to the original and keep whichever file is smaller.
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