What iMessage is
iMessage is Apple’s end-to-end encrypted messaging service, used to send and receive messages in the Messages app on iPhone, iPad, Mac, Apple Watch, and Apple Vision Pro. According to Apple’s support documentation, when someone sends a message to your email address or phone number using iMessage, all Apple devices set up to receive messages for that address or number receive it, keeping conversations in sync. Some iMessage features require an Apple Account.
How it differs from SMS and RCS
Points from the official support documentation:
- Channel and cost: iMessage texts go over Wi-Fi or cellular service and do not count against SMS, MMS, or RCS allowances in your cellular messaging plan (cellular data rates may apply).
- Blue and green bubbles: when the other person also uses iMessage, bubbles appear in blue; SMS, MMS, and RCS messages appear in green. A green send button means the message goes through SMS, MMS, or RCS.
- Encryption: iMessage is end-to-end encrypted, and an encrypted conversation shows “Encrypted” at the top; SMS/MMS conversations carry no such protection.
- RCS: when iMessage isn’t available, Messages can send the text as RCS instead; RCS is provided by your carrier, not by Apple.
Features and boundaries
The official documentation lists features such as text formatting, editing, unsending, scheduling, backgrounds, polls, Memoji, drawings, collaboration, and group conversation management, along with reporting spam to Apple and screening unknown senders. iMessage is available only on Apple devices; conversations with users on Android or other platforms fall back to SMS/RCS or use other messaging apps.
Discussion in the show
In Weekly #005’s chapter “Instinct：订房、商旅与信任” (Instinct: booking, business travel, and trust), Xiangyang Qiaomu described registering the AI booking assistant Instinct and said conversations with the friend who invited him went either through iMessage or through WhatsApp in the Chinese transcript; he discussed whether such chat-app-based product entries work for users in China. This is a participant’s observation of an overseas product, not a comment on iMessage’s own features. The episode 005 chapter has the full context; an English transcript is not available.
Frequently asked questions
How is iMessage different from SMS?
iMessage goes over Wi-Fi or cellular data, does not count against texting allowances, and is end-to-end encrypted between Apple devices with blue bubbles; SMS, MMS, and RCS go through carrier channels and appear in green bubbles. See the Apple support guide.
Can iMessage be used on Android or Windows?
No. The official documentation lists iPhone, iPad, Mac, Apple Watch, and Apple Vision Pro as the supported devices; messages to Android users are sent via SMS or RCS instead.
Is iMessage secure?
iMessage is end-to-end encrypted, encrypted conversations show “Encrypted” at the top, and Contact Key Verification can further verify contacts; SMS/MMS conversations are not protected in this way while being sent.
What if iMessage activation fails?
Activation normally requires a network connection, a signed-in Apple Account, and a phone number that can receive text messages; follow the iMessage activation guides on the Apple Support site.