How to Batch Convert Images Using macOS Preview

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 accidentally take lots of photos on your iPhone in Apple's HEIC format, for instance, you can use Preview on your Mac 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.

  2. 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.

  3. 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.

  4. Select Edit -> Select All from the Preview menu bar, or use the Command-A keyboard shortcut to select all the open images.

  5. Select File -> Export Selected Images... from the menu bar.

  6. Choose a location to export your converted images.

  7. Click the Options button in the Export window.

  8. Drag the Quality slider to the desired level (keep an eye on the file size).

  9. 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.

  10. 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.

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How to Electronically Sign a PDF Using Preview on Mac

When you receive a PDF document by email that you must sign, the process of printing out the file, signing on the dotted line with a pen, scanning the signed document and sending it back can be a rather tedious task. Fortunately, Apple has added the ability to electronically sign a PDF document using Preview, a program that comes preinstalled on every Mac running OS X Lion or later.

MacRumors PDF Signature
The steps involved to electronically sign a PDF using Preview on Mac are quite simple and will save you valuable time, especially if you have multiple documents, contracts, forms or other paperwork to sign. If you are worried that your virtual signature will look bad, rest assured that you can create your signature by using the trackpad or holding up your signature on paper to a Mac's built-in iSight camera. Continue reading "How to Electronically Sign a PDF Using Preview on Mac"

How to Convert Several Images into a Single PDF Using Preview

Over the years, Adobe's PDF file type has become a universally accepted method for sharing digital documents. The format's cross-platform adoption means the documents can be viewed on almost any mobile device or computer, so it's no surprise to find that macOS includes native support for viewing and creating PDF files.

In the Preview app, for example, it's possible to create a single multi-page PDF document out of several separate image files. The feature is particularly useful if you need to share a number of scanned documents over email or digitize something for reference. Keep reading to learn how it's done.
Continue reading "How to Convert Several Images into a Single PDF Using Preview"

How to Get the Most Out of Apple’s macOS Preview App

All of Apple's Macs come with Preview, a feature that's built into macOS. Preview is the default app that opens up whenever you view an image or a PDF, and it actually has quite a few useful tools built into it, which we've explored in the latest video over on our YouTube channel.

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  1. Editing a Clipboard Image - If you copy an image to your Clipboard from another app, you can quickly edit what's on your clipboard in Preview. To do so, copy an image, open the Preview app, and use the Command + N keyboard shortcut. Alternatively, choose File --> Open New From Clipboard in the menu bar.


  2. Filling Out Documents - When you open up a PDF in Preview, there's a whole toolbar of tools that you can use to fill out blank boxes. To access these tools, select the Markup icon (a pen in a circle).


  3. Signing Documents - With the Markup tools for editing PDFs, you can even virtually sign a document with your own signature. From the Markup toolbox, choose the signature icon, and select "Create New." From here, you can sign using your trackpad, or sign a white piece of paper with a pen and then hold it up to your Mac's camera. Both of these techniques work remarkably well, making it simple to get a virtual signature onto a digital document.


  4. Quickly Remove an Image Background - Preview is no match for software like photoshop, but there are some basic image editing tools included. If you want to remove the background from an image like a logo, there's a quick way to do so, with the steps outlined in detail in the video above. This feature really works best on images with a lot of contrast, such as a colorful logo with a white background.


  5. Photo Editing - In the same Markup toolbox that's been used for most of these tips, you'll find some basic photo editing tools for adjusting color, exposure, and other simple parameters. To open up these image editing tools, click on the little icon that looks like a triangle. You'll see options for exposure, contrast, saturation, temperature, tint, highlights, shadows, and sharpness, plus there's a histogram for more advanced edits.


  6. Adding and Removing PDF pages - If you open up a PDF in Preview, you can remove unnecessary pages or add additional pages. Using the Edit options in the menu bar, select Insert --> Page from File to add a new document to an existing PDF. Deleting is as simple as selecting the thumbnail view, selecting a thumbnail, and selecting delete. You can also use the sidebar to rearrange pages with simple drag and drop gestures.
If you've never really delved into the Preview app beyond viewing an image or PDF, it's well worth checking out some of the more advanced features. Have a favorite Preview feature we missed? Let us know in the comments.

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