What iMessage is, and how to turn it on
iMessage is Apple's own messaging between Apple devices: blue bubbles, end-to-end encrypted. How to tell it from SMS, how to switch it on, and what to check when it won't activate.
iMessage is the messaging built into the Messages app on iPhone, iPad and Mac. Stiger works inside it, so it has to be on before Stiger does anything. This page is the short version: what it is, how to tell whether you are using it, and how to switch it on. The steps are Apple’s, and the sources are linked at the bottom.
What it is
Apple’s own wording: with iMessage, messages go to another iPhone or another Apple device over Wi-Fi or cellular data. Texts, high-resolution photos and videos, documents and links all travel that way. Your conversations are end-to-end encrypted, so they can’t be read while they’re sent between devices, and Apple marks that with a lock icon at the top of the conversation.
Messages in the same app can also go out as RCS or SMS/MMS, which is how you reach people who don’t have an Apple device. The difference you can see is the bubble:
- Blue bubbles are iMessage.
- Green bubbles are SMS, MMS or RCS. Apple says SMS/MMS messages aren’t end-to-end encrypted. RCS can be, but only with iOS 26.5 or later and a carrier that supports it; Apple shows an “Encrypted” label with a lock icon when it is.
Which one a conversation uses depends on whether iMessage is switched on for you and whether the person on the other end uses it too.
Turn it on
On an iPhone, Apple’s steps are:
- Open Settings.
- Tap Apps, then tap Messages.
- Turn on iMessage.
- To choose which phone numbers and email addresses you use with iMessage, tap Send & Receive and pick from the list under “You can receive iMessages to and reply from”.
It can take a moment to activate. If your screen doesn’t match, check the iOS version: Apple’s guide has a version selector, and the menu layout differs between releases.
Activating iMessage with your phone number needs SMS messaging. Depending on your carrier you might be charged for that SMS. If a prompt says your network provider may charge for SMS used to activate iMessage and FaceTime, tap Turn On to allow it. A phone number also needs an active SIM or eSIM behind it.
If it won’t turn on
You might see “Waiting for activation”, “Activation unsuccessful” or “Unable to contact the iMessage server”. Apple’s list, in the order it gives it:
- Check that you have a cellular or Wi-Fi connection, the latest iOS, and the right time zone (Settings, General, Date & Time).
- Turn iMessage off in Settings, Apps, Messages. Do the same for FaceTime in Settings, Apps, FaceTime. Restart the iPhone, then turn both back on.
- Wait. Apple says it can take up to 24 hours for your carrier to verify the number, and that you should make sure your carrier lets you send and receive international SMS. A spinning gear next to the number means the phone is already trying to verify it, and there is no need to keep switching iMessage off and on.
- Use an email address instead of a number: Send & Receive, then choose the address.
- If you set up a new iPhone on iOS 26 and added the eSIM later, iMessage does not activate on its own: turn it off and back on in Settings, Apps, Messages.
- If the same number shows twice under Send & Receive after updating to iOS 26, an inactive SIM with that number is the cause. Apple’s fix is iOS 26.1 or later, or removing the inactive SIM.
Apple also describes accounts that are blocked from iMessage for reported spam. In that case you can still use SMS, MMS or RCS with iMessage turned off, or iMessage with an email address.
Where Stiger fits
Stiger is an iMessage extension: you find it among the iMessage apps inside a conversation, and the sticker it makes is sent through iMessage. Blue bubbles are the supported case. What SMS, MMS or RCS would do to a Stiger sticker I haven’t measured, so a green-bubble conversation is not something to rely on.
Two things iMessage on its own does not do: it doesn’t hide who you talk to or when, and it doesn’t protect a phone that someone else is holding. The longer read on both is What iMessage actually keeps private.
Sources, read on 2026-10-11:
- Set up Messages on iPhone, Apple iPhone User Guide
- What is the difference between iMessage, RCS, and SMS/MMS?, Apple Support, published 11 May 2026
- Add or remove your phone number in Messages or FaceTime, Apple Support, published 13 May 2026
- If you can’t turn on or sign in to iMessage or FaceTime on your iPhone, Apple Support, published 14 September 2026
- If you can’t activate iMessage with your phone number in iOS 26, Apple Support, published 2 April 2026