by Anthony 

November 16, 2022

Resizing photos on a Mac is a breeze. You can either resize them manually in the Preview app or you can automate the process down to a single click using Quick Actions. In this post I’ll explain both methods. 

I recently went trekking in the Himalaya, which offers amazing photo opportunities in every direction you look.

As you can imagine I took hundreds of photos which, thanks to modern phones and camera technology, are extremely large in size. Whilst this is great for viewing on a computer they tend to be too big to easily send to friends and family, so I intend to scale a copy of them down to 1920 by 1080 pixels.


How To Resize A Photo on Mac - The Manual Method

  • Open your images in Preview
  • Select Tools in the menu, followed by Adjust Size
  • Choose a custom size or use Apple’s preset sizes.
  • Press OK
  • Press CMD + S to save your changes. 

Start by opening your photos in Preview. Select them all by pressing CMD + A.

If you have lots of photos (say over 50), and depending on the processing power of your Mac, you may need to select them in batches.

Having selected them all, or a batch of them, click on Tools in the menu followed by Adjust Size. 

How To Resize Images On Mac (without additional software)

This will open a window offering you several options to adjust the size of your photos.

the adjust size window in the preview app

You can set a custom size or Apple offers you some preset sizes by clicking on the drop down menu. You can also change the measurement, so if you’re familiar with Pixels you might prefer to use percentages.

When you’re happy click OK and your photos will be resized. If you’re not happy with them you can undo the change by selecting them and pressing CMD Z, or, undo from the edit menu. 

undo changes in the preview app

Remember to press File in the menu and Save, or CMD + S,  to confirm your changes.

How To Resize Images on a Mac - The Automated Method

  • Open the Automator app.
  • Select Photos from the Library.
  • Click and drag Scaled Images to the Workflow.
  • Choose Add to preserve the original image.
  • Choose a destination folder for the resized image.
  • Set the width of the image in pixels
  • Save the automation.
  • Right click on the original photo.
  • Choose the Quick Action from the context menu.
  • The new resized image will be saved in the destination folder.

If you have a lot of photos or resize images regularly, as I do, you can automate the process by creating a Quick Action. Quick Actions are available for all sorts of different file types, not just images. You access Quick Actions by right clicking on a file and you should see the option in the context menu. 

the context menu display quick actions

 For photos and images, Apple has already pre-configured some Quick Actions that can be accessed from the context menu. These include converting the file type of an image, say from PNG to JPG, or vice-versa, and removing the background of an image. 

To create a new Quick Action to resize a photo, we use the Automator app. 

Open the Automator app. Select Quick Action from the available options and press Choose.

choose quick action in the automator app

In the automation tool you navigate from from left to right. Start by choosing Photos from the library on the left. In the middle section of the app you should now see all the different automations available for working with our Photos.

list of automations for photos

Click on Scale Images from the list and drag it to the Workflow section on the right of the app. 

drag scaled images options to workflow

You will likely receive a warning explaining that this automation will modify the original file, in this case reducing the dimensions of the photo. The app is therefore giving us the option to create a copy, thereby preserving the original photo. This is a good idea so choose Add. 

warning message that original photo will be altered

You should see two elements in the workflow. The first is going to create a copy of the photo and save it to a folder. It will then resize the copy to the dimensions we set. By default, it will save the copy to the Desktop, but you can change this or create a new folder. I chose to create a sub-folder on my Desktop called Resized.

creating a destination folder in automation app

As with Preview, you can set the new dimensions either in Pixels or in Percent. If working in Pixels the number you add in the workflow should be the width you wish your scaled down photos to have. It will automatically adjust the height based on the current dimensions.  

setting the new pixel size in automation app

That completes the setup of our Quick Action. Now it’s just a matter of saving and giving it a name. Press CMD + S, or File and Save from the menu. The name you provide will be the name of the Quick Action, which you’ll see in the context menu when right-clicking on your photo. 

saving the new quick action in the automation app

Having saved your Quick Action you can exit the Automator app. 

Select the photos you wish to resize, right click on them and in Quick Actions on the context menu you should see your new Quick Action you just created. The first time you run the new Quick Action, you might be prompted to allow Finder permission to access the folder. This is fine, so click OK.

the new quick action in the context menu

You’ll notice a little cog icon in the menu bar confirming that the automation is processing. Once the cog icon disappears the job is complete and your resized photos should be in the destination folder.

cog icon showing quick action is processing

Key Takeaways

  • You can use Preview to manually adjust the size of a photo or image.
  • Alternatively, use the Automator app to create a Quick Action.
  • You can create a Quick Action to automate the process of resizing a photo. 
  • Remember to make a copy of your images preserving the originals.
  • CMD + S will save your changes, CMD + Z will undo any changes.

If you found this post useful, don’t forget to check out my YouTube channel for lots of tips and tricks on all your favourite apps.

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