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How to Batch Convert Images Using macOS Preview

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Apr 12, 2001
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Preview-app-250x250.jpg
There are many third-party apps available for Mac that will batch convert images for you (Permute is one example). And then there's Preview, the powerful file viewer that's built into macOS.

Preview will happily convert several images for you in one go. If you have lots of photos on your Mac in Apple's HEIC format, for instance, you can use Preview to quickly convert them to the more accessible JPEG format.

In fact, what's not obvious to many users is that Preview is capable of converting files in 18 different image formats, including the following:
  • GIF
  • HEIC
  • ICNS
  • JPEG
  • JEPG-2000
  • KTX
  • Microsoft BMP
  • Microsoft Icon
  • OpenEXR
  • PBM/PGM/PPM
  • PDF
  • PNG
  • PVRTC
  • Photoshop
  • PostScript
  • QuickTime Movie
  • TGA
  • TIFF
The secret to accessing all of the available format export options in Preview is with the Option (?) key. Keep reading to learn how it's done.

How to Batch Convert Images in Preview
  1. In a Finder window, hold down the Command (?) key and individually click all the images you want to convert; if they're grouped together consecutively, hold down Shift and click the first and then the last file, and all of them will be selected.
    how-to-batch-convert-images-in-preview03-800x411.jpg

    Double-click one of the selected images to open them all in Preview. If Preview isn't your default image viewer, right-click (Ctrl-click) instead and choose Open With -> Preview from the dropdown menu.
  2. Click inside the Preview sidebar. (if it's not showing, click the View Menu button and select Thumbnails.) Alternatively, if you're using the Contact Sheet view, drag a box over all the images to select them.
    batch-convert-images-in-Preview-800x500.jpg

    Select Edit -> Select All from the Preview menu bar, or use the Command-A keyboard shortcut to select all the open images.
    how-to-batch-convert-images-in-preview-03-800x498.jpg

    Select File -> Export Selected Images... from the menu bar.
    how-to-batch-convert-images-in-preview02.jpg

    Choose a location to export your converted images.
    how-to-batch-convert-images-in-preview-08-800x447.jpg

    Click the Options button in the Export window.
    how-to-batch-convert-images-in-preview04-800x445.jpg

    Drag the Quality slider to the desired level (keep an eye on the file size).
  3. Select an image type from the Format dropdown. Pro tip: Hold down the Option (?) key when you click the Format button to reveal several more image formats available to you.
    how-to-batch-convert-images-in-preview05.jpg

    Click Choose.
A progress indicator bar will replace Preview's Export window. Once it has completed you'll find your exported images in the chosen location and format, ready for use in your projects.
Note that you can also batch resize images using the method outlined above. After Step 4, select Tools -> Adjust Size... from the menu bar, input the resolution you want all the selected images to take, and click Resize. Note: You may need to select all the images again for export.

Article Link: How to Batch Convert Images Using macOS Preview
 
Article Link
https://www.macrumors.com/how-to/batch-convert-images-to-different-formats-using-macos-preview/
Last edited:
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timmyh said:
If anyone can tell me how to access all of Preview's format conversion options in Automator, I'd be very grateful.

View attachment 799202
Click to expand...

Looks like Automator hasn't been updated and I doubt it will. You could add a terminal command to your Automator Workflow that runs the 'sips' command to do additional filetype conversions. (i.e. sips -s format jpeg filename.gif --out newfilename.jpg)
 
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Good to know, although I would generally recommend lossless png over lossy jpeg for little difference in file size. You lose some quality each time you save in jpeg, but not png.
 
It is a shame normal things have been so well hidden, there is a need for these "How-to" articles.
 
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How do you know which buttons have "hidden" features that are revealed using the Option button? Is there a GUI style convention (say, the way the button is shaded when you hover over it, or something?) that suggests that more hidden options are available? Or is it just impossible to tell and you have to try the Option button everywhere you go to try to reveal hidden treasure... i.e., is it considered more of an "easter egg" kind of thing to delight the ones that stumble across these treasures and allow them to write a 'macOS Secrets revealed' kind of book or article? It just seems so stupid... it's something I'd expect from some hopeless nerd Android programmer (or the self indulgent programmers of the Tesla user interface), not from Apple. E.g., how's my mother in law supposed to figure it out?
 
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It's like Kai Krause got a job at Apple to hide really useful things from everyone.... So stupid these great formats aren't in plain site.i guess just as bad is that the save dialog doesn't leave options open as every other app does which has similar set up
 
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outskirtsofinfinity said:
How do you know which buttons have "hidden" features that are revealed using the Option button?
Click to expand...

My best guess is it's for stuff they need to do all the time within Apple but don't really want normal people doing it - like the way the OPTION key allows the user library folder to appear. Remember the Apple design philosophy is to minimize your options. So ironically, the "option" key is anti-Apple - it's there because some people simply need the options. But it doesn't mean Apple has to like that fact or make it easy for you. :)
 
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This is great but it trashes the Create Date.
We need a way to do this but preserve the metadata.

Apple has a real problem with photos and videos in general because actions create a new file giving it a new create date and there is no way to access a separate original image date in the given fields - and its not clear if that is even preserved anywhere buried in the meta data.
This wrecks the timelines of photo and video collections.
Does anyone have a simple solution for this?

I'd like to resize my whole Photos library because it takes up too much space and the individual images don't need to be that big but I obviously din't want to lose the date markers and with the timeline of the library.
 
Solomani said:
I agree. And to be fair, Notes is also one of those free built-in apps that has gained superb features in the past year or two.
Click to expand...
With the addition of links between Notes, Notes is only now approaching the functionality of Hypercard which was on all Macs 30 years ago!
 
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