10 free ways to compress images on Mac

Check out these 10 easy tools to compress images on your Mac to save space without compromising quality.

As cameras and screen resolutions increase, the photos and screenshots you take can run into several MBs. The large file means it occupies more space (on Mac, iCloud, SSD) and takes longer to send via Messages, email, and so forth. One way to address this is by reducing the image file size.

Note that compressing and decreasing the photo size certainly lowers the picture quality a bit. But in most cases, you won’t notice much difference.

Image file sizes depend on these factors

Image dimensions: A 1920 x 1080 image will have a larger file size than the same image at 720 x 480.
Image format: For most pictures, JPG/JPEG tends to have a smaller file size than PNG. But PNG is better if your image is mainly text-based or has very few simple colors.
Image content and color depth: If there are many black portions in the image instead of white, it can have a smaller file size.
Camera type: Pictures taken by the front iPhone camera or the MacBook’s webcam usually have a smaller file size than the primary camera, which runs into several megapixels.
Flash: Using flash while shooting pictures will result in an image with a larger file size.
Screen resolution: The screenshot file size of my new retina 13-inch MacBook Pro is far larger than that of my non-retina 13-inch MacBook Pro. This is because the sharper screen has more pixels and image dimensions, resulting in bigger screenshots.

Now that you know the basics about image file size, here are some quick ways to convert large images on Mac to smaller sizes.

1. Reduce image file size by changing its format

I take dozens of screenshots on iPhone and Mac every day for GeeksChalk articles. On supported Mac models running macOS Tahoe 26 or later, the Screenshot app’s Options menu lets you choose the capture format: SDR (Most Compatible) captures in standard dynamic range using the PNG image format, while HDR captures in high dynamic range using the HEIF image format. So depending on that setting, your Mac screenshots arrive as either PNG or HEIF files.

If the screenshot only has text, I almost always keep it in PNG format. But if the image has graphics (like the screenshot of Mac’s Desktop), I convert it to JPG in 99.9% of cases. This is because JPG offers almost the same picture quality as PNG but significantly reduces file size. At times, the file size reduction is up to 98%!

If you take lots of screenshots, you can use an easy Terminal command to change Mac’s screenshot file format to reduce size.

2. Compress file size by resizing the image

If you have a large image with a width and height of 4000 px and 2800 px, it likely runs to several megabytes. To address this, you can resize and reduce the dimensions to something like 2000 px by 1400 px. This will lower the file size.

To see the image dimensions, select the file in the Finder, then choose File > Get Info, or press Command-I. An information window opens for the item, and the item info can include file size, image dimensions, and more. To make the image file size even smaller, compress the resized image.

3. Compress photos with a right-click

You can use the handy Finder Quick Actions menu to compress images on Mac running macOS Monterey and later.

Select one or more images, then Control-click (or right-click) them.
Choose Quick Actions > Convert Image.
Click the Format pop-up menu and pick a format. JPEG is suitable unless you wish to change it. A checked Preserve Metadata box means you want to keep the photo details like date, time, location, etc. You can uncheck that if desired.
Click the Image Size pop-up menu and choose Small, Medium, Large, or Actual Size. Note that Actual Size may offer significant savings only when you change the format, such as when you’re converting PNG to JPEG. If you stay with the same format, choosing Actual Size won’t reduce the file size by much.
Finally, click Convert to [Format Name] to reduce the image file size and save it in the same location as the original files.

Tip: Switch the Finder window to List view, then click the Size column heading to sort files by their size. Click the column name again to reverse the sort order.

4. Use Preview on Mac to compress pictures

Preview offers the tools to reduce the file size of one or multiple images.

Compress one image

Double-click to open the picture in the Preview app.
From the top menu bar, choose File > Export.
Click the Format pop-up menu, then choose a format. HEIC isn’t compatible everywhere, but it offers a significantly smaller file size. You may also choose JPEG or others as needed. If you don’t see the file type you want, press and hold the Option key and click the Format pop-up menu to see specialized or older formats.
If you choose JPEG or JPEG-2000, a quality slider appears. Drag it to lower the quality.
Once you’re satisfied with the file size, type a new name or choose a new location if you want, then click Save.

Tip: After compressing the image, if you feel the quality is unusable, follow the same steps with the original image and go easy on the quality slider.

Compress images in bulk/batch

Before you start, make sure Preview is set to open your files together. Go to Preview > Settings, click Images, then select Open groups of files in the same window under "When opening files." Otherwise each picture opens in its own window and there’s no shared sidebar to select from.

Select multiple images in the Finder folder by holding the Command key or pressing Command-A to select all.
Control-click and choose Open With > Preview.
Press Command-A to make sure all image thumbnails are selected in the window’s sidebar. If you don’t see the sidebar, choose View > Thumbnails.
From the top menu bar, choose File > Export Selected Images.
Click Show Options or Options from the bottom.
Set the format and drag the quality slider to adjust it.
Finally, click Choose to compress all images and save them.

How to fix "Cannot export selected items" in Mac’s Preview app?

If you see a popup saying, "Cannot export selected items," click OK. Now, hold the Command key and unselect images of different formats from the sidebar of the Preview app. After this, follow the above steps to compress images.

In case this doesn’t work, go back to the Finder folder, switch to List view, and click the Kind column heading to sort your images by format. Now, select only the pictures of a particular format (JPEG, PNG, etc.) and open them in Preview to compress.

5. Compress images using Mac’s Photos app

Like the Preview app, you can reduce image file size using the macOS Photos app.

Select one or more pictures in the Photos app.
Press Shift-Command-E, or choose File > Export > Export [number] Photos from the top menu bar.
Click the Photo Kind pop-up menu and choose the file type for the exported photos.
To set the size and quality, click the down arrow beside the Photo Kind pop-up menu, then use the JPEG Quality pop-up menu (JPEG files only) and the Size pop-up menu to compress the images.
Click Export, choose where to save the exported photo files, then click Export.

6. Use photo compression apps

The Mac App Store has several apps that let you compress images. Search for something like "compress images" in the App Store.

On my Mac, I use Compress Photos & Pictures, which is an iPhone and iPad app. But since I use a MacBook with Apple silicon, I can install this app on my Mac, and it works as flawlessly as it does on iPhone.

Search for "Compress Photos" in the Mac App Store and click "iPhone & iPad Apps" from the top to get this app.

Once you have Compress Photos & Pictures on your Mac, the steps are effortless. You can add photos from the Photos app and save the compressed images back to the Photos app.

7. Use online sites to compress images

Finally, one more method I use daily to compress images for my posts is via online services.

One web search for "compress images" will list hundreds of such sites. Three that I like and have been using for many years are:

Feel free to give them a try. But you must know that you will be uploading the images to the site’s servers (except for Squoosh, which compresses images locally in your browser). Since I compress screenshots with non-personal or non-sensitive information, I see no harm in using these. But for compressing images of identity cards, driving licenses, personal photos, etc., I use the offline methods mentioned above.

Furthermore, changing PNG to JPG using Finder or Preview may add black borders to your images. However, iLoveIMG.com does not do that.

8. Compress images with a Terminal command

This is the method I reach for when I have a folder of 40 screenshots to get through. Your Mac already ships with a command-line tool called sips (Scriptable Image Processing System), and it converts and resizes images faster than any app I’ve tried. Nothing to download, nothing to install.

Open the Terminal app, type cd followed by a space, drag the folder of images into the Terminal window, and press Return. You’re now working inside that folder.

To convert one PNG to a JPEG at 80% quality:

sips -s format jpeg -s formatOptions 80 image.png --out image.jpg

The formatOptions value sets the JPEG quality. You can give it a percentage like 80, or one of the words low, normal, high, or best.

To convert every PNG in the folder in one shot:

for f in *.png; do sips -s format jpeg -s formatOptions 80 "$f" --out "${f%.png}.jpg"; done

And to shrink the dimensions while you’re at it, add -Z followed by a pixel value. This resamples the image so its height and width aren’t greater than the size you specify, which keeps the aspect ratio intact:

sips -s format jpeg -s formatOptions 80 -Z 2000 image.png --out image.jpg

Tip: As long as you include --out, sips writes a new file and leaves your original alone. Leave --out off and it edits the file in place. I always include it.

9. Compress images using the Shortcuts app

If Terminal isn’t your thing, Shortcuts gets you to the same place with a couple of drag-and-drops. And you only have to build it once.

Open the Shortcuts app and create a new shortcut.
Add the Resize Image action and set the width you want. Set it to Ask Each Time if you’d rather be prompted on every run.
Add the Convert Image action below it, choose JPEG, and lower the quality. This action can also strip metadata if you don’t want location details travelling with the file.
Double-click the shortcut, click the Shortcut Details button, then select Use as Quick Action.

Now Control-click an item in the Finder, then choose Quick Actions > [your shortcut] from the menu. The shortcut is also available in the Quick Actions menu in the Preview pane of a Finder window.

This fixes my one real complaint about the built-in Convert Image quick action in method 3. That one only offers Small, Medium, Large, and Actual Size. Here you set the exact pixel width you need.

10. Make your own quick action with Automator

Automator has been on the Mac for decades, and it still does one thing better than anything else on this list: it drops a compression step of your own design into the right-click menu, permanently.

Open the Automator app and choose Quick Action for the document type.
At the top of the workflow area, set "Workflow receives current" to image files in Finder.
From the Actions library on the left, drag Copy Finder Items into the workflow first. Don’t skip this one. The action that follows overwrites whatever it touches, and this is what keeps your originals safe.
Drag Scale Images in below it, then set the size by pixels or by percentage.
Choose File > Save and give it a name like "Shrink for web."

The quick action shows up right away. Control-click any image, choose Quick Actions, and your new item sits in the list alongside Rotate Left and Convert Image.

Tip: Automator’s image actions can resize, but they can’t set a JPEG quality percentage the way sips and Shortcuts can. If quality control matters more to you than the right-click convenience, use method 8 or 9 instead.