Reduce file size jpg
For many photos, the file size is 2 - 7 MB. For sending 10 photos by mail to explain something, 250 Kb is large enough. We select the photos, open in preview, select all, export, choose lower resolution, and then all photos are resized with new name.
With old macos this worked, but not anymore. Need photo by photo
iMac 21.5″, macOS 10.13