iMessage is turned on in Settings, under Messages

iMessage is Apple's encrypted messaging service that sends texts over Wi-Fi or cellular data instead of through your phone carrier's SMS system. On iPhone 15, it's enabled by default when you set up the phone, but you may need to turn it back on if it's been disabled or if you're setting up a new device.

To turn on iMessage: open Settings, tap Messages, then toggle the iMessage switch to on (it will turn green). Your phone will connect to Apple's servers and verify your phone number and Apple ID. This usually takes a few seconds, though it can take longer if your internet connection is slow.

Once iMessage is on, any text you send to another iPhone, iPad, or Mac user will automatically send as an iMessage (shown in blue) instead of as a regular SMS text (shown in green). If you send a message to someone with an Android phone, it will automatically fall back to SMS.

Key Takeaways

  • iMessage is enabled in Settings > Messages by toggling the iMessage switch on.
  • Your phone number and Apple ID must be verified before iMessage works, which usually takes a few seconds after you toggle it on.
  • iMessage messages appear in blue; regular SMS texts appear in green.
  • iMessage only works when sending to other Apple devices — messages to Android phones automatically send as regular texts.
  • You need an active internet connection (Wi-Fi or cellular data) for iMessage to work, but SMS texts will send without it.

What to do if the iMessage toggle is greyed out

If the iMessage switch in Settings > Messages is greyed out and you cannot tap it, your phone cannot reach Apple's activation servers. This usually means your internet connection is too weak or blocked.

First, make sure you are connected to Wi-Fi or have cellular data turned on. Go to Settings > Wi-Fi or Settings > Cellular and confirm you have a working connection. If you are on public Wi-Fi (at a coffee shop or airport), the network may be blocking Apple's servers — try switching to cellular data instead.

If you still cannot enable iMessage after switching connections, restart your phone: press and hold the side button and either volume button until the power-off slider appears, then slide to power off. Wait 10 seconds, then press and hold the side button again until the Apple logo appears. After the phone restarts, go back to Settings > Messages and try toggling iMessage on again.

Signing in with your Apple ID

iMessage uses your Apple ID to verify your identity with Apple's servers. When you first toggle iMessage on, your phone automatically signs in using the Apple ID you used to set up your iPhone 15. If you are signed into multiple Apple IDs on your phone, iMessage will use the one associated with your primary account.

You can see which Apple ID iMessage is using by going to Settings > Messages > Send & Receive. Your phone number and email addresses linked to that Apple ID will be listed. If you want to use a different Apple ID for iMessage, you will need to sign out of the current one in Settings > [Your Name] > Sign Out, then sign in with the other ID.

Why iMessage might turn off on its own

iMessage can disable itself if your phone loses internet connection for an extended period, if you sign out of your Apple ID, or if you turn off cellular data and Wi-Fi simultaneously. Some carrier settings updates can also reset iMessage to off, though this is rare on iPhone 15.

If iMessage keeps turning off, check whether you are accidentally toggling it off in Settings > Messages. If you are not doing that, try updating your phone's software: go to Settings > General > Software Update and install any available updates. Outdated carrier settings can sometimes interfere with iMessage — you can manually update these by going to Settings > General > About, which will prompt a carrier settings update if one is available.

Using iMessage with multiple devices

If you own multiple Apple devices (an iPad, Mac, or Apple Watch), you can send and receive iMessages on all of them using the same Apple ID. This means a text sent to your phone number will appear on your iPad and Mac as well.

To set this up, turn on iMessage on each device using the same Apple ID. On your iPhone 15, go to Settings > Messages > Send & Receive and confirm your phone number is listed. On your iPad or Mac, open Messages settings and sign in with the same Apple ID — your phone number should appear automatically once it is verified.

If you want to receive iMessages on your Mac or iPad but not on your iPhone 15, you can turn off iMessage on your phone while leaving it on on the other devices. Just toggle iMessage off in Settings > Messages on your iPhone.

iMessage versus SMS: when each one is used

iMessage and SMS are two different systems, and your iPhone 15 automatically chooses which one to use based on who you are texting. When you send a message to someone with an iPhone, iPad, or Mac, it sends as iMessage (blue bubble). When you send to an Android phone or other non-Apple device, it sends as SMS (green bubble).

iMessage has some features that SMS does not: you can see when someone is typing, send high-resolution photos and videos, use read receipts, and send messages that disappear after a set time. SMS messages are limited to 160 characters and lower image quality. However, SMS works on any phone and does not require an internet connection — it uses your phone carrier's network instead.

If you are texting someone with an iPhone but the message appears in a green bubble, it means iMessage failed to send and your phone fell back to SMS. This usually happens if the other person has turned off iMessage, if their phone is offline, or if your internet connection is too weak.

Frequently Asked Questions

Do I need to pay for iMessage?

No. iMessage is free and included with every iPhone. You only need an internet connection (Wi-Fi or cellular data). You do not pay per message, and there are no hidden fees.

Can I use iMessage without an Apple ID?

No. iMessage requires an Apple ID to verify your identity with Apple's servers. You set up an Apple ID when you first set up your iPhone 15, so you should already have one.

What happens if the person I'm texting has iMessage turned off?

Your message will automatically send as a regular SMS text instead (it will appear in a green bubble on your end). They will receive it normally, but you will not see typing indicators or read receipts.

Can I turn off iMessage for just one contact?

No. iMessage is either on for all contacts or off for all contacts. However, if someone has iMessage turned off, your messages to them will automatically send as SMS, so you do not need to manually switch.

Why are my iMessages not sending?

Check that iMessage is toggled on in Settings > Messages and that you have an internet connection. If the message has a red exclamation mark, try turning iMessage off and back on, or restart your phone. If it keeps failing, the other person may have iMessage turned off, in which case your message will send as SMS instead.