When you receive a message on your iPhone, it will appear on your lock screen. You could unlock your iPhone and open Messages to reply, or you can just reply right there from the lock screen. But this means anyone else can reply to your messages right there from the lock screen, too.
If you want to prevent anyone from pranking you and possibly causing a serious misunderstanding, you can turn this feature off.
To do this, open your iPhone’s settings and tap “Touch ID & Passcode”.
Next, you will need to enter your passcode.
Once you have opened the Touch ID & Passcode settings, scroll down to the section that says, “Allow Access When Locked”.
You’ve got some choices here and if you really want to make your iPhone extra secure and private, you could deselect all these items.
The option that interests us most however, is “Reply with Message”. Tap that off so you (or anyone else) can no longer reply to messages from your iPhone’s lock screen.
Now, when messages appear on your lock screen, the only way to reply to them will be to unlock your iPhone and open Messages.
This doesn’t have to be an all-or-nothing proposition, though. You could just disable lock screen replies whenever you’re going to be around friends or mischievous uncles and re-enable it when you’re alone again. It’s up to you.