The basic difference and how to turn it on
iMessage is Apple's messaging system that runs over internet data or Wi-Fi instead of your phone's text message plan. If you have an iPhone, iPad, or Mac, iMessage is already installed — you just need to turn it on in your settings. Once enabled, your iPhone automatically sends messages as iMessage (shown in blue) when messaging other Apple device users, and falls back to regular text messages (shown in green) when messaging Android phones or older devices.
To turn on iMessage, open Settings on your iPhone, tap Messages, then toggle on iMessage. Your phone will connect to Apple's servers and register your phone number and Apple ID. This takes a few seconds to a few minutes depending on your connection. Once it's active, you don't have to do anything else — the system handles routing automatically.
The main reason people switch is that iMessage includes read receipts (you can see when someone has read your message), typing indicators, and higher-quality photo and video sending. iMessage also works over Wi-Fi, so you can message even without cell service. Regular text messages use your carrier's SMS network and count against any text message limits in your phone plan, though most plans today include unlimited texting.
Key Takeaways
- iMessage turns on in Settings > Messages > toggle iMessage on, and your phone registers automatically with Apple's servers.
- iMessage messages appear in blue bubbles and only work between Apple devices; messages to Android phones automatically switch to green SMS text messages.
- iMessage includes read receipts, typing indicators, and better photo quality, but requires internet or Wi-Fi to send.
- If you switch from iPhone to Android later, you should turn off iMessage first or you may not receive text messages from iPhone users.
What happens when you message someone without iMessage
When you send a message to someone with an Android phone or an older device that doesn't support iMessage, your iPhone automatically sends it as a regular text message instead. The message bubble turns green instead of blue, and you won't see read receipts or typing indicators — those features only work in iMessage conversations.
This automatic switching means you don't have to think about it. You can message your iPhone-using friends in blue iMessage and your Android-using friends in green SMS from the same Messages app, and each conversation behaves according to what the other person's device supports. If someone upgrades from Android to iPhone, the next message you send them will go through iMessage automatically.
Read receipts and typing indicators
iMessage lets you see when someone has read your message and when they're typing a response. These features are turned on by default once iMessage is active. In any conversation, if you see "Delivered" under your message, it reached the other person's device but they haven't opened the message yet. Once they open it, it changes to "Read" with a timestamp.
You can turn off read receipts if you don't want people to know you've seen their messages. Go to Settings > Messages and toggle off Send Read Receipts. This hides your read status from everyone, though you'll still see when others have read your messages if they have read receipts turned on. Typing indicators (the three dots that appear when someone is composing) cannot be turned off individually — they're part of iMessage and work both ways.
iMessage over Wi-Fi and without cell service
One of iMessage's main advantages is that it works over Wi-Fi alone, without needing cell service. If you're in an area with no signal but connected to Wi-Fi, you can still send and receive iMessages. Regular text messages require cell service, so if you lose signal, SMS won't work until you're back in range.
This is especially useful in places like airplanes (with Wi-Fi), remote areas, or buildings with poor reception. Your iPhone will show "iMessage" at the top of the conversation if it's sending over iMessage, and "SMS" if it's using your carrier's network. You can also see which method was used by looking at the message bubble color — blue for iMessage, green for SMS.
Photo and video quality differences
iMessage compresses photos and videos less aggressively than SMS text messages do. When you send a photo through iMessage, the recipient gets a higher-quality version than they would through a regular text message. This is because iMessage uses internet data, which can handle larger file sizes, while SMS is limited by the older text message standard.
If you send a photo to an iPhone user via iMessage, they'll see it at near-original quality. If you send the same photo to an Android user, your iPhone automatically converts it to SMS, and the quality drops noticeably. The difference is most obvious with screenshots, detailed photos, or videos — iMessage keeps them sharp, while SMS makes them blurry and compressed.
What to do if you're switching away from iPhone
If you plan to switch to an Android phone or another non-Apple device, turn off iMessage before you switch. Go to Settings > Messages and toggle off iMessage. This tells Apple's servers to stop routing messages meant for your phone number through iMessage.
If you don't turn it off, iPhone users will keep sending you iMessages, but your new Android phone won't receive them — those messages will sit on Apple's servers waiting for an Apple device to pick them up. You might miss important messages for days or weeks. Apple recommends turning off iMessage at least a day before switching phones. If you've already switched and aren't receiving messages from iPhone users, you can turn off iMessage remotely by visiting Apple's account page at iforgot.apple.com, though it's easier to do it before you switch.
Troubleshooting when iMessage won't turn on
If iMessage won't activate, first check that you're signed in to iCloud with your Apple ID. Go to Settings > [Your Name] and make sure you're logged in. iMessage needs an active Apple ID to register. If you're signed in but iMessage still won't turn on, try signing out and back in, or restart your phone.
Make sure you have an active internet connection — iMessage needs Wi-Fi or cell data to register with Apple's servers the first time. If you're on a corporate or school network, the firewall might be blocking iMessage registration. Try connecting to a different Wi-Fi network or use cellular data instead. If none of that works, contact Apple Support, as there may be an issue with your account or device.
Frequently Asked Questions
Does iMessage cost money?
No. iMessage is included with every iPhone and uses your existing internet connection — either Wi-Fi or your cellular data plan. There's no separate charge from Apple. You only pay for the data or Wi-Fi you use, the same as any other app.
Can I use iMessage on Android?
No. iMessage only works on Apple devices: iPhone, iPad, iPod Touch, and Mac. Android phones cannot send or receive iMessage. If you message an Android user from your iPhone, the message automatically converts to a regular SMS text message.
What if someone has iMessage turned off?
Your message will send as a regular text message instead. You'll see a green bubble instead of blue, and you won't have read receipts or typing indicators. The other person can turn iMessage back on anytime, and future messages will use iMessage again.
Will turning on iMessage affect my text message plan?
No. iMessage uses data or Wi-Fi, not your text message allowance. Messages to Android users still use SMS and count toward your plan if you have a limit, but most plans today include unlimited texting. You can check your plan details with your carrier if you're unsure.
Why are some message bubbles blue and some green?
Blue bubbles are iMessage, which means the message went to another Apple device over the internet. Green bubbles are SMS text messages, which means the message went to an Android phone or non-Apple device over your carrier's network. Your iPhone chooses automatically based on what device the other person has.