Is it possible to stop a message from being delivered on the iPhone?
Short guide: If you're looking to quickly stop a message from being delivered, quickly open the Control Centre by swiping up from the bottom edge of the screen and toggle Airplane Mode on. If performed quickly, your message will display as undelivered and you can prevent it from sending before re-enabling your data connection.

We've all sent text messages we regret, and with autocorrect changing our words it's easier than ever to send an ill-advised message. So, it's worth learning how to stop a text message from being delivered on the iPhone.
The good news is that it is possible to cancel a text message from being delivered, but only if you are quick - so if you have already sent it, sorry, it may end up on Damn You Autocorrect after all. If you can cancel the message before it is sent you can prevent it from being delivered.
Updated 5 July 2016 with general updates.
See also:
  • What to do when your iPhone isn't connecting to internet
  • How to retrieve deleted text messages on iPhone
  • How to send a text when your friend isn't getting your iMessages
  • Why is my iPhone asking if it can update carrier settings?

Can I unsend an iPhone message?

How to cancel an iPhone message
Unfortunately, it's not possible to unsend a message. Google has an unsend feature to Gmail, but text messaging with Apple is, for now, a one-way service and once the message has been delivered the other person can read it.
So, you need to cancel the message before it is delivered. Fortunately, it turns out this is easier than you imagine, but you have to be quick.

How to cancel an iPhone message

Use AirPlane Mode to cancel a message
The trick is to turn off the iPhone mobile connection before the message has been delivered - and luckily sometimes it can take a good few seconds to go through. When you tap Send, you'll see a blue bar move across the screen. If you can cancel the message before this bar hits the right-hand side you will stop the message from sending. Here is how to cancel an iPhone message:
  1. Open Messages and create a new text message. It's easier to practice with photo (as this takes longer to send) but any text will do.
  2. Tap Send.
  3. Quickly swipe up from the bottom of your screen to bring up Control Centre.
  4. Tap Airplane Mode to on.
Swipe down to get rid of Control Centre and return to the Messages app. If you did it quickly enough you'll see a red Not Delivered alert next to the text or image. This lets you know that the message hasn't been sent.
This trick works pretty well with images, and with SMS Text messages but we find iMessages (the ones with the blue balloon) tend to go through quite quickly. A lot of it depends on how fast your connection is. However, it's a great trick to know in a pinch.