What's the difference between green messages and blue messages?

Green and blue represent SMS messages sent and received by operators and Apple iMessage respectively.

Green SMS

The messages displayed in green belong to the messages of traditional operators, that is, they are generally charged according to the number of messages. There is no limit to the sending of this short message, and it can be used regardless of the mobile phone model. This kind of short message is used by traditional operators, namely mobile, telecom and Unicom. In addition, you can also see a prompt with the words "SMS/MMS" in the SMS text input box.

Blue SMS

Blue SMS is a service provided by Apple for iOS devices to send information through the network for free, that is, iMessage information, whether using wireless network or mobile network. This kind of short message can only be used if both parties use iPhone, and both parties have opened iMessage service and have network connection.

Extended data:

Similar to MMS, iMessage not only allows users to send text to other iOS and OS X users via Wi-Fi, 2G, 3G or 4G LTE, but also can transmit documents, images, videos, locations, contact information and group information, thus providing standard SMS and multimedia SMS services for most devices with iOS 5 and above.

IMessage is implemented on iPhone, iPad, iPod touch running iOS 5 and Mac running OS X Mountain Lion through the "Messages" program. Owners of these devices can register multiple email addresses on Apple's network. If the communication operator supports it, the iPhone owner can register an Apple account with this phone number.

In the information program, the user can see the input status of the iMessage user at the other end. When the other party starts to reply, a light gray ellipsis will appear in the message bubble. After starting a conversation on one iOS device, users can continue to send messages on another device.

Some specific functions of iMessage are effective in systems above iOS5 or OS X Mountain Lion, but only on iPhone can information programs send short messages to non-iOS systems or devices where iMessage is temporarily unavailable. On the iPhone, green buttons and bubbles mean that the current communication is based on SMS; On all iOS devices, blue buttons and bubbles indicate that information is currently being transmitted through iMessage.

All messages sent through iMessage are encrypted and can be tracked by sending feedback. If the receiver activates the "reading feedback" function, the sender will be able to see that the former has read the information.