While there are tons of applications that you can use to batch resize images, nothing beats the command line to get things done quickly and efficiently. In Mac, you can easily batch resize images with this command:
1. Open the terminal and “
cd” to the folder that contain all the images that you want to resize. Alternatively, you can open the Finder and drag the folder to the terminal to paste the file path.
2. Type this command:
sips -Z 320 *.jpg
and all the jpg files in the folder will be resized to 320px wide. You can change the width or the file format.