How to Delete Multiple Messages on the iPhone
Don't let unnecessary messages flood your iPhone Messages inbox. Delete older messages or texts that you no longer need. Once you've cleared out the unwanted clutter, you will be able to concentrate more on the messages that require your attention. You may also find it helpful to delete sensitive texts as a precaution to safeguard your privacy. Deleting multiple messages on the iPhone is a basic task anyone can perform and no technical expertise is needed.
Open the "Messages" application on your iPhone.
Tap the "Edit" button on the left side of the toolbar at the top of the screen. A red "-" button appears next to each message in your Messages list.
Tap the red "-" button next to a message you want to delete. A red "Delete" button will appear to the right of the selected message. Tap the "Delete" button to delete the message. Repeat for each message you want to delete.
Tap the "Done" button on the left side of the toolbar to exit the Edit options.