iMessage
iMessage is an instant messaging service developed by Apple Inc. and launched in 2011. iMessage functions exclusively on Apple platforms – including macOS, iOS, iPadOS, and watchOS – as part of Apple's broader strategic approach to inter-device integration, sometimes referred to as the "Apple ecosystem".[1]
This article is about the instant messaging service. For the app, see Messages (Apple).Developer
Core features of iMessage, available on all supported platforms, include sending text messages, images, videos, and documents; getting delivery and read statuses (read receipts); and end-to-end encryption so only the sender and recipient can read the messages, and no one else, including Apple itself, can read them. The service also allows sending location data and stickers. On iOS and iPadOS, third-party developers can extend iMessage capabilities with custom extensions, an example being quick sharing of recently played songs.
Launched on iOS in 2011,[2] iMessage arrived on macOS (then called OS X) in 2012.[3] In 2020, Apple announced an entirely redesigned version of the macOS Messages app which adds some of the features previously unavailable on the Mac, including location sharing and message effects.
Features[edit]
iMessage allows users to send texts, documents, photos, videos, contact information, and group messages over the Internet to other iOS or macOS users. iMessage is an alternative to the SMS and MMS messaging for most users with devices running iOS 5 or later. The "Send as SMS" setting under Messages will cause the message to be sent via SMS if the sender does not have an active Internet connection. If the receiver has no Internet connection, the message should be stored on a server until a connection is restored.
iMessage is accessible through the Messages app on an iPhone, iPad or iPod Touch running iOS 5 or later, or on a Mac running OS X Mountain Lion or later. Owners of these devices can register one or more email addresses with Apple. Additionally, iPhone owners can register their phone numbers with Apple, provided their carrier is supported. When a message is sent to a mobile number, Messages will check with Apple if the mobile number is set up for iMessage. If it is not, the message will seamlessly transition from iMessage to SMS.[31]
In Messages, the user's sent communication is aligned to the right, with replies from other people on the left. A user can see if the other iMessage user is typing a message. A pale gray ellipsis appears in the text bubble of the other user when a reply is started. It is also possible to start a conversation on one iOS device and continue it on another.[31] On iPhones, green buttons and text bubbles indicate SMS-based communication; on all iOS devices, blue buttons and text bubbles indicate iMessage communication.
All iMessages are encrypted and can be tracked using delivery receipts.[32] If the recipient enables Read Receipts, the sender will be able to see when the recipient has read the message. iMessage also allows users to set up chats with more than two people—a "group chat".
With the launch of iOS 10, users can send messages accompanied by a range of "bubble" or "screen" effects.[33][34][35] By holding down the send button with force, the range of effects is surfaced for users to select from.
With the launches of iOS 14 and macOS 11 Big Sur, users gain a myriad of features such as the ability to pin individual conversations, mention other users, set an image for group conversations, and send inline replies. Additionally, more of the features from the Messages app on iOS and iPadOS were ported over to their macOS counterpart.[36]
With the launch of iOS 15.2, Apple added automated blurring of photos containing explicit images that are sent to underage users. The feature relies on scanning the photos on the device and can optionally be set to alert the underage user's parents if explicit material is received. The feature was originally launched only for the US with a later expansion to the UK, Canada, Australia and New Zealand. The feature remains regionally restricted for the rest of the world.[37][38]
With the launch of iOS 16, Apple added the ability for users to edit and unsend sent iMessages. Users can unsend an iMessage for up to 2 minutes after it being sent, and can edit it for up to 15 minutes. Users also have the ability to recover deleted messages for up to 30 days.[39]
Technology[edit]
The iMessage protocol is based on the Apple Push Notification service (APNs)—a proprietary, binary protocol.[40] It sets up a Keep-Alive connection with the Apple servers. Every connection has its own unique code, which acts as an identifier for the route that should be used to send a message to a specific device. The connection is encrypted with TLS using a client-side certificate, that is requested by the device on the activation of iMessage.
Each message recipient's public keys are retrieved from Apple Identity Service (IDS), "Apple's directory of iMessage public keys, Apple Push Notification service (APNs) addresses, and phone numbers and email addresses that are used to look up the keys and device addresses."[41] Each message is individually encrypted for each recipient device in a conversation. Message attachments are encrypted and uploaded to iCloud to be retrieved separately by the recipient. Messages are stored on Apple servers for up to 30 days.[42]