Mac OS batch resize images

You can easily batch resize groups of images within Mac OS by using the included Preview app, that is, taking a group of pictures set at one or various resolutions, and collectively resize them all together in a group to a new resolution.

• Select all the images you want resized in the Finder, and then open them within the Preview app
• From Preview, select all of the images that you want to batch resize from the left-side thumbnail drawer (command + a will select them all)
• Now, go to the menu labeled “Tools”, and then choose “Adjust Size”
• Enter a value for what you want the new width and height to be
• Next, navigate to the “File” menu and click “Save All” or, to save a new version that is resized, choose “Export Selected Images…” or “Save As”