How to Generate Thumbnails with a Mac Quick Action

Here’s a quick guide to creating an Automator service (quick action) so that you can quickly batch generate thumbnails images from multiple imae files with a simple right-click.

macOS Automator Quick Action Panel Header Image
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Creating thumbnail images manually isn’t something that comes up very often anymore. When the web was younger, we’d have to manually generate thumbnail images that could be used as smaller, lightweight previews on web pages and could be linked to the larger image.

But as the web has matured, most of that has been automated by content management systems and website builders.

Nevertheless, there might still be times you need to create image thumbnails from a batch of images. Maybe you’re creating an image collage from hundreds or thousands of images. Or maybe you’re using a web platform or an offline HTML gallery that doesn’t automate the thumbnail creation. Or creating an old-school contact sheet.

There are many ways you could tackle this task. Batch export from Lightroom. Set up a Photoshop action. Use a free resizing tool as an online service of a software app like XnView.

But if it’s something you find yourself doing often and use a Mac, there’s another option to add into the mix: create an Automator Quick Action.

On the plus side, it’s very simple and convenient. It means you can set it up to access with a simple right-click or keyboard shortcut.

On the negative side, you only have very limited control over the output. And you only have a choice of three sizes: 128px , 96px, or 72px. Which is pretty restrictive. So if you need more flexible controls, another tool might be a better choice.

With that said, here’s a quick guide to setting up an Automator Quick Action that will generate thumbnails from any number of image files.

Open the Automator App

You can find it under:

/Applications/Automator.app

Set Type of Action

When it asks you for the type of document, choose Quick Action. (In older versions of Mac OSX, it was called Service.)

Screenshot: Mac Automator Resize Image - Choose Quick Action

Then hit the Choose button.

Set Workflow Options

It will have added an initial section to the workflow area at the right. For the top option next to “Workflow receives current”, select the “image files” option. Leave the rest at their defaults (you can customize the image and color fields if you like, but there’s no need to).

Set Processing Type

From the Library in the left column, click on Photos to narrow the available actions. In the list of actions (second from left), scroll down and choose “Create Thumbnail Images.” Or use the search bar to search for “thumbnail”.

Click and then drag to the right-hand workflow panel.

Screenshot - macOS Automator Quick Action Create Thumbnail Images

Next, in the Rotate Images Panel, click on the Options button.

Screenshot - macOS Automator Quick Action Create Thumbnail Images

And then check the box for “Show this action when the workflow runs.”

Screenshot - macOS Automator Quick Action Create Thumbnail Images

What this will do is when you run the workflow, it will popup with the option for what size you want: 128px , 96px, or 72px. If you don’t check that box, it will only run whatever rotation it’s showing in that panel.

You can also select the suffix that will be applied to the output thumbnail images. The default is _tn, which is logical enough.

Export Automator Quick Action

That’s all you need to do with the workflow section. Now you just have to export it as an action.

In Automator’s main menu, go to File > Export.

Export Automator Action

In the Export As section, name it to whatever you like. Something like Generate Thumbnails seems like a logical choice for this particular action. Then choose where you want to save it. This is only a temporary spot for it, so it makes sense to put it somewhere you’ll find it quickly, like the Desktop. Then click the Save button.

Install Automator Quick Action

Next, find the file you just saved using Finder or, if you put it on the Desktop, just go to the Desktop. Double-click on the file.

You’ll get a popup asking if you want to install it as a quick action (or service).

Screenshot - Mac Automator Resize Image - Quick Action Installer

Click on the Install button. The .workflow version will then be automatically moved, and you can now use right-click in Finder to convert the file using the quick action.

Using Your New Quick Action

The app you’ve just created is available immediately. There’s no need to restart the computer or Finder.

To use it, select the image or images in Finder or your preferred Mac file browser (I use Forklift; Commander One is another popular option). 1

Then right-click and go to Services and choose from the list.

It works on one image file or multiple files. If for some reason you’re mixing image files amongst other files in the same folder, it is possible to add a filter earlier in the workflow so that it only applies to image files. Explore the Filter Finder Items action under Files & Folders in the actions Library panel (far left).

Things Worth Knowing

Automator is baked into macOS, so there’s no need to install anything and buy anything.

The app you’ve just created is available immediately. There’s no need to restart the computer or Finder.

You have very limited flexibility with this method, and you only have a choice of three sizes: 128px , 96px, or 72px.

Tip: Add a Keyboard Shortcut

You can also apply keyboard shortcuts to your Quick Actions. To do that, go to:

Automator > Services > Services Preferences

Then, find the service on the list and click on it. You’ll see a small “Shortcut” button appear to the right of the name. When you click on the Shortcut button, you’ll get a field where you can just press the keyboard combination you want to use for it.

Just be sure to avoid other global shortcut combinations–there’s no warning message if you step on an existing shortcut’s toes–it just won’t work as expected.

What is macOS Automator?

Automator is a tool that’s baked right into macOS. It doesn’t receive a lot of attention, but it’s really, really handy to have. You can find it under:

/Applications/Automator.app

Basically, automaton gives you visual tools in the form of building blocks to build workflows. So you can accomplish a bunch of useful tasks without writing any code (although you can add Applescript code, if you need something more customized).

Even better, some Mac apps add actions and tools to Automator that extend the power and functionality of Automator. This usually happens automatically in the background when you install the app. Sadly, an excellent collection of Automator tools to interact with Photoshop that was put out by Ben Long no longer works with current versions of macOS (although Photoshop has its own separate toolkit for creating Photoshop actions which can be incredibly powerful but work differently from Automator actions).

Where Automator excels is in saving time and adding convenience with time-consuming, repetitive tasks such as this. But it can also be surprisingly powerful if you want it to be.

  1. If you’re specified Finder in the top panel where it says “Service Receives Selected…”, then use Finder for this. :) []
David Coleman / Photographer
by David Coleman

I'm a professional freelance travel photographer based in Washington DC. Seven continents, up mountains, underwater, and a bunch of places in between. My images have appeared in numerous publications, and you can check out some of my travel photography here. More »