How to Compress an Image on Mac: A Step-by-Step Guide


Ted Stinson

Compressing an image on a Mac is a simple task that can be completed in just a few steps. By using the built-in Preview application, you can easily reduce the file size of an image without losing too much quality. This is especially useful for sharing photos online or via email, where file size limitations may apply.

Step by Step Tutorial: How to Compress an Image on Mac

Before we dive into the step-by-step process, it’s important to understand that compressing an image will reduce its file size by decreasing its resolution or quality. This can be useful if you need to save storage space or make the image easier to share.

Step 1: Open the image in Preview

Open the Preview application and select the image you want to compress.

Preview is the default application for viewing images and PDFs on a Mac, so you should be able to simply double-click the image file to open it in Preview.

Step 2: Click on the "Tools" menu

In Preview, click on the "Tools" menu located in the menu bar at the top of the screen.

The "Tools" menu contains various options for editing and manipulating your image, including the ability to compress it.

Step 3: Select "Adjust Size"

From the "Tools" menu, select "Adjust Size" to open the image resizing options.

In this menu, you can specify the dimensions and resolution you want for your compressed image.

Step 4: Adjust the image resolution

Adjust the image resolution by changing the width and height values or by adjusting the resolution value.

Remember that decreasing the resolution will reduce the file size, but it will also affect the image quality. Make sure to strike a balance between file size and quality that suits your needs.

Step 5: Click "OK" to apply changes

After adjusting the resolution, click "OK" to apply the changes and compress the image.

Once you click "OK," the image will be compressed, and you can save it as a new file or replace the original.

After completing these steps, your image will be compressed and ready to be shared or stored. You can now enjoy more space on your Mac and faster upload times for your images.

Tips for Compressing an Image on Mac

  • Always make a copy of the original image before compressing it, just in case you’re not happy with the results.
  • Consider the purpose of the image before compressing it. If it’s for professional use, you may not want to reduce the quality too much.
  • Be mindful of the image format. Some formats, like JPEG, are already compressed, so further compression may not be as effective.
  • Use the "Preview" option to check the quality of the image after compression before saving it.
  • If you need to compress multiple images at once, consider using a third-party app that offers batch processing.

Frequently Asked Questions

How much can I compress an image on a Mac?

The amount you can compress an image depends on the original file size and the desired quality. It’s a balancing act between reducing file size and maintaining enough quality for your needs.

Will compressing an image on a Mac reduce its quality?

Yes, compressing an image typically reduces its quality to some extent, as you’re decreasing the number of pixels or the amount of data stored in the file.

Can I compress any image format on a Mac?

Most common image formats, such as JPEG, PNG, and TIFF, can be compressed using Preview on a Mac. However, some proprietary formats may require specialized software.

Can I undo the compression if I’m not happy with the results?

If you save the compressed image as a new file, you can always revert to the original. If you replace the original, you cannot undo the compression without a backup.

Is there a way to compress images without losing quality on a Mac?

While some quality loss is inevitable with compression, using formats like PNG or adjusting the compression level can help minimize the loss.


  1. Open the image in Preview.
  2. Click on the "Tools" menu.
  3. Select "Adjust Size."
  4. Adjust the image resolution.
  5. Click "OK" to apply changes.


Compressing an image on Mac is a breeze once you know how to do it. Whether you’re looking to save space, speed up your website, or send images via email, understanding how to compress an image can be a real game-changer. By following the steps outlined in this article, you’ll be well on your way to mastering this useful skill.

Remember, the key is finding the right balance between file size and image quality. It’s always a good idea to keep a backup of the original image, just in case you need it later. And if you’re working with a large number of images, there are plenty of third-party apps available that can make the process even easier.

So, next time you find yourself needing to compress an image on your Mac, don’t sweat it. With these tips and tricks up your sleeve, you’ll have that image ready to go in no time. And who knows? Maybe you’ll even impress your friends with your newfound tech-savviness. Keep experimenting, and happy compressing!