iMessage is a proprietary messaging protocol developed by Apple that is only supported on Apple's Messages app as a business decision. The Messages app is exclu

iMessage is a proprietary messaging protocol developed by Apple that is only supported on Apple's Messages app as a business decision. The Messages app is exclusive to iOS, macOS, and other Apple OSes. iMessage has a broader feature set than the older (but open) SMS and MMS protocols, such as higher-quality audio and video, more controls over chat groups, reaction emojis, and end-to-end encryption. In the Messages app, messages sent with the iMessage protocol are displayed in blue bubbles and messages sent with SMS/MMS are displayed in green bubbles. The Messages app automatically uses iMessage if the recipient has a phone number registered to use iMessage, and otherwise falls back to SMS/MMS. In group chats, the Messages app only uses iMessage if all participating phone numbers also use iMessage. On iPhones (and iPads), Apple does not allow apps other than Messages to access the device's SMS/MMS functionality. This means every iPhone user's only SMS/MMS app automatically switches to iMessage when possible unless the user specifically deregisters their phone number from the iMessage system. With Apple's restriction, iOS users cannot switch to a different messaging app that supports a combination of on-device SMS/MMS and a newer protocol that is not iMessage. In the U.S., some iPhone users who are accustomed to features found in iMessage but not supported by SMS/MMS are upset when they are in a conversation with a phone number that is not registered to use iMessage. This was originally due to SMS/MMS having fewer features than iMessage, but has evolved into a social signal for some U.S. iPhone users who are typically younger. This has led those iPhone users to stigmatize the green bubbles in Apple's Messages app and exclude Android users from their conversations.* The portion of Apple's conduct that is most applicable to FTC regulation, in my opinion, is not that Apple limits iMessage to Apple devices, but that Apple implements App Store restrictions to forbid iOS/iPadOS from supporting third-party SMS/MMS clients. * Why Apple’s iMessage Is Winning: Teens Dread the Green Text Bubble: https://www.wsj.com/articles/why-apples-imessage-is-winning-teens-dread-the-green-text-bubble-11641618009 https://www.wsj.com/articles/why-apples-imessage-is-winning-... (https://archive.ph/gGNel https://archive.ph/gGNel)