How to Resize an Image on Mac: a Step-by-Step Guide

So you have this huge image that seems to be taking too much space and you’d like to resize it.

Perhaps you downloaded it from one of top free stock photos sites, or you’ve taken a high-resolution screenshot for your blog, and now need to resize it.

No matter your situation, resizing images on a Mac is a lot easier than resizing images on an iPhone. Indeed, Mac users can resize images with built-in tools such as Preview, Pages, Mail and ColorSync.

If you’re resizing images on Windows, you still have access to inbuilt features, and some programs are available on both platforms.

In this article, we’re going to review all these methods and a few extra ones. We’ll also provide an overview of the pros and cons of each method. Finally, we’ll share best practices such as how to maintain image quality or how to batch resize images.

Let’s get started.

1. How to resize images on Macbook using Preview?

Step-by-step method to resize an image using Apple’s Preview on Mac

One of the easiest ways to resize images on Macbook without using Photoshop is to use the Preview app. It is conveniently installed on your Mac by default. Here is how it works.

What does the Resample image option do in Preview?

What is resampling?

Resampling an image means changing the number of pixels in the image as you resize it. Let’s uncheck the box on the previous example to see how it works.

First you’ll notice that you can no longer resize the image according to Pixels. This is understandable because this option changes the number of pixels, which is exactly what we don’t want to do since we’ve unchecked the option to resample images.

Let’s resize the image from the current 55×83 inches dimensions into 30×34 inches.

Let’s take a step back and understand what we just did: we’ve basically asked Preview to keep the same amount of pixels in the picture, while reducing its size by almost 50%. This means that the number of pixels per inch (PPI) will be increased since we have to squeeze the same amount of pixels in a smaller area. That’s why the resolution, which is defined by the PPI, increases from 72 pixels per inch to 133 pixels per inch after resizing the image.

When should you use resampling?

Resampling should be used if you’re trying to prepare images for the web or for print as you’ll fit your image’s number of pixels per inch (PPI) into specific PPI targets. For example, if your printer prints at 300 PPI, you could resize the image and check the “resample image” option until the PPI becomes 300.

Another situation where you’d want to use resampling is if you’d like to reduce the size of the image file. If you leave the box unchecked, the file size of the image will not change. If you check the box, the size of the image file will be reduced upon reducing the size of the image, to reflect the decrease in the total number of pixels in the image. To demonstrate this, we tried reducing the size of an image by 50% in preview:

• Without resampling: the image size increased from 1.7MB to 2.2MB!
• With resampling: the image size decreased from 1.7MB to 645KB.

Keep in mind though, that resampling is irreversible. That means that once you’ve lost those pixels, you can not get them back!

How to resize images without losing quality on a Mac?

The Preview app makes it easy to resize images without losing quality. All you need to do is to uncheck the option “resample image” to prevent Preview to reduce the number of pixels per inch, which is likely to decrease the quality of the image. This way, Preview will preserve the number of pixels in your image when resizing it, and therefore its quality will remain the same.

2. How to resize images on a Mac with Pages?

If you use the Pages app as your text editor on MacOS, you’ll find that it comes with a handy way to resize images in any Pages document.

After you’ve changed the values of the Width or the Height, your image’s dimensions will automatically be adjusted in the document.

Note that a quicker way to adjust the size of an image, but with less precision, is to click on an edge of your image and drag it to increase or decrease its size.

Pros

• Free and pre-built on MacOS
• Best way to resize images within a text document supported by Pages for Mac
• Ability to increase the size of the images very easily with the mouse

Cons

• No ability to do bulk image resizing
• Limited controls on the output file and on the image quality
• No resulting size estimate

3. How to resize an image on the Photos app on Mac?

We’ve previously seen how difficult it was for older iOS versions to resize photos in the Photos app on an iPhone. If you’re an Apple user, you know that resizing photos on an iPhone using the Photos app can be done by cropping it.

On Mac, you won’t need to crop the image. To quickly resize the image you’ll need to:

Note that the Photos app gives you good control about the output image: you can choose the type (JPEG, TIFF, PNG), the image quality (Low, Medium, High, Maximum) and the color profile such as aRGB or AdobeRGB. You can also add a title, specific keywords and a description to your photos.

Pros

• Free and pre-built on MacOS
• Fairly easy to use
• Ability to define the photo kind (JPEG, PNG, etc)
• Ability to control the quality to a certain extent
• Ability to apply a Color profile
• Unique features enables you to add title, keywords and description to your photos

Cons

• No ability to resize multiple images at the same time
• No ability to disable image resampling
• No way to know the final image file size prior to resizing

4. Resize Images Using ColorSync Utility

According to Apple, the ColorSync Utility app on Mac allows you to create color profiles to make sure that the colors of your photos appear to be the same across all your devices and upon printing. But apart from this main purpose, the ColorSync app also allows you to change the size of images and gives you some control over the quality of the resized image. Let’s deep-dive into it.

Pros

• Ability to set the quality and the DPI

Cons

• No unique feature, compared to other methods
• No way to know the final image file size

5. How to change the size of an image using the Mail App

Step-by-step method to reduce the size of your images in Mail on MacOs

If you’re trying to send a large image by email, you’d probably want to resize it to prevent your email to become oversized and be blocked by your recipient’s server or by your own mail server.

The method we’ll describe here works in all versions of Mac OS. Whenever you try sending an email that contains one or several images, the Mail app will give you the option to resize the image via a drop down menu. But contrary to the process of resizing an image on iPhone’s Mail app, the Mail app on MacOS will not proactively ask you to resize the image. You’ll need to keep it in mind.

Pros

• Perfect if you’re trying to send large photos by email
• Supports batch resizing of images
• The size of the email gives an idea on how big the attached images are

Cons

• No control over the quality of the image
• The email size information may not be very precise if the body of your email is very long

How to see the size of the message in the Mail app ?

MacOS’s Mail app conveniently displays the size of the email in the message header. If you’re trying to send one or several images and don’t have too much text in your email, this message size can give you a pretty good idea of how big your images are.

Importantly, the Mail, if your image is too big for the email to be sent by your email server, the message size will be in red color. If that’s the case, you’ll definitely have to reduce the size of that original image, or share them over a cloud storage service like WeTransfer or Google Drive.

Why is it important to resize images when sending an image via Gmail ?

If you’re using Gmail, you can not send emails larger than 25MB directly. So you’d need to first upload your image to Google Drive and share a link to that image on Google Drive within the body of your email. In reality, the maximum size of an image you can share via Gmail is even smaller than that because the process of encrypting your images and including them in your email relies on a protocol called MIME that increases the size of your email. This means that Gmail could force you to use Google Drive to send a photo even if the photo size is less than 25MB.

6. How to resize an image on Mac for wallpaper?

Adding a wallpaper to your Mac can set you to the right mood or mindset. It can be used as a constant reminder of what matters to you, help you stay inspired or motivated to excel at your craft. So let’s see how to resize your images for that purpose. Here is how you do it:

Pros

• Easy way to set a photo as your wallpaper
• Images can be automatically resized without the need to specify dimensions

Cons

• It can be quite frustrating to find the right dimensions and settings to perfectly fit an image into your computer’s screen
• Not much control of the quality of the image

7. How to resize images using Quick Actions on Mac?

If you have to resize images on a frequent basis using the same specific settings, you’d save a lot of time by creating a Quick Action on Automator. If this is all Greek to you, don’t panic. We’re going to take it step by step, first by quickly explaining what Automator is, and then getting right into how you can use it to resize pictures much faster than with the Preview app. And yes, you can resize multiple images at once using Automator’s Quick Actions.

What is Automator?

Automator is an application that is pre-installed on your Mac. It helps you automate tasks. Think about any repetitive task that you constantly do, such as renaming files, changing an image format, resizing an image, or creating PDF from images, etc. Chances are, you can easily program it by selecting pre-built tasks and creating a custom workflow in Automator that replaces all the manual tasks you’d need to do. If you’ve read our blog post about resizing images on iOS, this will probably remind you of the Shortcuts app which you can use to resize an image without cropping it on iPhone.