You can't change a message you've already sent, but you can switch how future messages are sent
Once a text message leaves your phone, it's already gone as an SMS (standard text). You cannot convert it to iMessage after the fact. What you can do is turn on iMessage so that future messages to other iPhone users automatically send as iMessages instead of texts — which gives you read receipts, typing indicators, and end-to-end encryption that regular SMS doesn't have.
The confusion usually comes from seeing a message appear in green (SMS) or blue (iMessage) in your conversation thread. That color is determined by how the message was sent at the moment you hit send. If you want blue messages going forward, you need to enable iMessage before you start typing.
Key Takeaways
- iMessage only works between Apple devices, so messages to Android users will still send as green SMS texts no matter what you do.
- Turn on iMessage in Settings > Messages > iMessage on any iPhone, iPad, or Mac you use regularly.
- Your phone needs an active internet connection (WiFi or cellular data) to send iMessages, but SMS texts work without data.
- If iMessage is on but a message sends as green, it means the recipient doesn't have an Apple device or iMessage is turned off on their end.
- Turning iMessage off and back on can fix problems where messages get stuck or fail to send.
Where to find the iMessage setting on iPhone
Open the Settings app on your iPhone. Scroll down and tap Messages. At the top of that screen, you'll see a toggle for iMessage. Tap it to turn it on. The toggle will turn green when it's active.
Your phone will connect to Apple's servers using your Apple ID and phone number. This takes a few seconds. Once it's done, the next message you send to someone with an iPhone will automatically send as iMessage and appear in blue.
If you use an iPad or Mac as well, you can turn on iMessage there too. Go to Settings > Messages > iMessage on iPad, or System Settings > Messages > iMessage on Mac. Use the same Apple ID on all your devices so messages sync across them.
Why some messages still send as green SMS even with iMessage on
A message sends as SMS (green) instead of iMessage (blue) for one of three reasons: the person you're texting has an Android phone, they have an iPhone but iMessage is turned off on their end, or your internet connection dropped at the moment you hit send.
You'll see this most often when texting Android users. iMessage only works between Apple devices. No setting on your phone can change that. If you need encrypted messaging with Android users, you'd need to use a different app like Signal or WhatsApp instead.
Sometimes an iPhone user has iMessage off because they switched from iPhone to Android and turned it off to stop missing messages, or they're having technical problems. You can ask them to check their Settings > Messages > iMessage toggle, but you can't force it on from your end.
What to do if iMessage won't turn on
If the iMessage toggle won't switch on, or it turns on but then turns itself back off, your phone usually needs to reconnect to Apple's servers. The fastest fix is to turn iMessage off, wait 10 seconds, then turn it back on.
If that doesn't work, make sure you're signed into iCloud. Go to Settings > [Your Name] at the top > iCloud and check that you're logged in with your Apple ID. iMessage won't set up without an active iCloud account. If you're not signed in, tap iCloud, enter your Apple ID and password, and try turning iMessage on again.
Check that you have an internet connection. iMessage needs WiFi or cellular data to work. If you're on WiFi, try switching to cellular data for a moment, or vice versa. Sometimes the connection is unstable and switching helps.
If none of that works, restart your phone. Hold down the power button until you see "slide to power off," slide it, wait 30 seconds, then power it back on. This clears temporary glitches that prevent iMessage from connecting.
The difference between iMessage and SMS for your daily use
iMessage messages are encrypted end-to-end, meaning Apple's servers can't read them. SMS texts are not encrypted. If privacy matters to you, iMessage is the better choice — but only for conversations with other iPhone users.
iMessage shows you when someone is typing (the three dots appear), and it shows you when they've read your message (it says "Delivered" or "Read" below the message). SMS doesn't do either. You also get reactions — you can long-press a message and add an emoji response without sending a separate text.
iMessage works over WiFi, so if you're somewhere without cellular service but you have WiFi, iMessage will still send. SMS requires a cellular connection. This is useful when you're on airplane WiFi or at a place with spotty cell service but good WiFi.
The downside: iMessage needs an internet connection. If your WiFi drops and you have no cell data, iMessage won't send until the connection comes back. SMS will send over cellular even if WiFi is off.
How to turn iMessage off if you need to
Go to Settings > Messages > iMessage and tap the toggle to turn it off. Your messages will now send as SMS to everyone, including other iPhone users. The messages will appear in green.
You might want to do this if you're having problems with messages not sending, or if you're switching to Android soon and want to make sure you don't miss texts while the switch happens. Some people also turn it off temporarily to troubleshoot whether a problem is iMessage-related or something else.
If you're switching to Android permanently, turn off iMessage before you hand over your iPhone number. If you don't, iMessages sent to your old number will still try to route through Apple's servers and you won't receive them on your new Android phone. Apple has a tool to deregister your number, but turning off iMessage first is the simplest step.
What happens when you text someone who doesn't have iMessage
Your phone automatically detects whether the person you're texting has an iPhone with iMessage on. If they don't, the message sends as SMS instead, and it appears in green. You don't have to do anything — your phone handles it.
This is why you might see a mix of blue and green messages in the same conversation thread. Every message to that person that goes to an iPhone gets sent as iMessage (blue). Every message that can't reach iMessage falls back to SMS (green). It's automatic.
If someone recently switched from iPhone to Android, their number might still be registered in Apple's iMessage system for a few hours or days. During that time, your messages might try to send as iMessage and fail. This is why people switching phones are sometimes told to turn off iMessage on their old phone before they switch — it clears them out of the system faster.
Frequently Asked Questions
Can I send iMessage to someone with an Android phone?
No. iMessage only works between Apple devices. If someone has an Android phone, your messages will automatically send as SMS (green text) instead. If you need encrypted messaging with Android users, use Signal, WhatsApp, or another third-party app that works on both platforms.
Why do my messages say "Delivered" but not "Read"?
The person received your iMessage but hasn't opened the conversation yet, or they have read receipts turned off. Go to Settings > Messages and look for "Send Read Receipts" — if it's on, others will see when you read their messages. If it's off, they won't.
What if iMessage says "waiting for set up"?
Your phone is trying to connect to Apple's servers but hasn't finished yet. This usually takes a few seconds to a few minutes. Make sure you have WiFi or cellular data on, and that you're signed into iCloud. If it stays stuck, turn iMessage off and back on, or restart your phone.
Do I need to pay for iMessage?
No. iMessage is free. It uses your internet connection (WiFi or cellular data), so you only pay for the data plan you already have. There's no separate charge from Apple.
If I turn off iMessage, will I lose old messages?
No. Turning iMessage off only affects how new messages are sent going forward. All your old messages stay in the Messages app, whether they were iMessage or SMS. You can turn iMessage back on anytime without losing anything.