Messages is 5.32 GB and probably contains every message ever received or sent. I could use help with this one. I wanted to delete entire message strings but couldn’t figure out how.
To delete the entire string with one person or group, go to the list of people in messages, not the listing of messages for one person, and swipe left on the person. An option in red to Delete should appear. Tap and poof! Gone.
Also, photos sent or received in Messages take up space. If you really want to keep the images, save them to Photos, then delete them from within the Message (tap and hold on the image in Messages, tap "More" and then Trash).
