As you get your images open in Preview, you’ll see one selected image in the center and the rest as thumbnails on the side.Select Open With… and click on Preview.Select all images you want to resize in a Finder folder and right-click on them.Here’s a step-by-step for batch resize there: You can actually batch resize both with Preview or apps like batch editing and watermarking tool PhotoBulk. Resize multiple images at onceīut you don’t have to go resizing your photo collection on Mac one by one. To keep both your original image and the resized (or otherwise edited) one, go to File > Export… and save your changes as a new file. Note that by default, Preview saves all edits in the existing file. In the pop-up window, set your desired image dimensions and click OK: In the Markup mode, click Adjust Size icon:.Find Markup icon in the top menu bar of the Preview window (for narrow images, the icon often hides behind the >.Open an image in Preview (simply double-click on the file to open it and Preview is the default option in most cases).If you go to Finder > Applications and scroll through the apps, you’ll find Preview, an image viewing and editing app that comes with your Mac. Macs actually have a built-in image editing software that can resize images on your Mac.