If you don't have Photoshop (or Photoshop Elements) you can still resize your images for web. We recommend https://tinyjpg.com/ because it's light weight and simple. However, sometimes you have too many files, or you don't have a fast internet connection.
I'll briefly show you how to resize for web using Preview, the default image/pdf viewer installed on your Mac.
But first, a word of warning... you should copy/duplicate your images into a different folder so that you have backups of your files. Never edit the size/resolution of your images with out backing them up.
After you have duplicated the images, the first step is to simply open your Preview application, then go to File > Open and browse for the files you want to edit.
One thing to look out for: Preview wants file types to be the same. So you'll notice I had to skip the ".tiff file"... however, if you're making ".tiff" files chances are you have Photoshop already!
It's also a good idea to resize images that have the same aspect ratio (shape). Once you open the files in preview you'll see on the left side thumbnails of all the individual files.
If you don't see this make sure that "thumbails" are selected, go to View > Thumbnails.
Now scroll down to the bottom of the Thumbnails and while holding the Shift key click on the last one. Or just use the select all keyboard shortcut "Command + A" and select all your images.
Now you can proceed to edit them all with just one step! In the top toolbar go to Tools > Adjust Size. This will open up a window where you can set a standard width or height. For these images (since they are landscape orientation) I will choose a fixed width.
Our full screen page layout will work well for these images, so we'll set the width to 1680px. We are basing this width on the 16:10 ratio that our lookbook editor uses. These standard pixel dimensions are used on many devices. So you could use any of these widths (1680, 1920, or even 2560).
Enter "72" as the pixels per inch and then click OK. You'll see how much size you'll reduce... here I go from 16.3 MB for all 13 images to just 6.3 MB!
Once you hit OK your files will be updated and ready to upload. While not perfect, Preview can help you resize images quickly, no need for Photoshop!