If your iPhone is running out of storage space, we have a ton of great tips at How to make space on an iPhone. See 19 Ways to Make Space on your iPhone.
But one quick fix is to delete all or at least many messages from your iPhone. Using this method I reduced the space taken by messages from 2.2GB to just 112MB.
How do you quickly delete all messages from an iPhone?
My iPhone was carrying 2.2GB of messages because my iPhone was set (as a default) to Keep Messages “Forever”.
Follow these simple steps to clear all messages from your iPhone at once.
1. Go to "Settings" from the iPhone’s homepage.
2. Scroll down to to "Messages".
3. Go to "Message History".
4. Go to “Keep Messages”.
5. There are three options: 30 Days, 1 Year, and Forever.
6. The quickest way to delete all messages is to select all older than 30 days, or all messages older than a year old.
7. Confirm that you want to delete the old messages and attachments by clicking the "Delete" button.
This won’t delete ALL messages, but it will substantially save you storage space.
But look what it saved on my iPhone. First see the 2.2GB of messages that I had with the default Keep Messages Forever option.
Now see the results when I selected 1 Year – down to 885MB.
Finally, I selected to Keep Messages for just 30 days, and reduced the storage space taken up by Messages to just 112MB!
And you can then individually delete all the messages from the past 30 days through the iPhone's Messages app itself – a lot easier now that you have wiped the rest by following those steps above.
If you change your mind see How to Restore Deleted iPhone Messages.