iMessage vs SMS
iMessage is an Apple internet-based messaging system, while SMS is carrier-based text messaging. iMessage can support richer features in Apple-to-Apple chats, and SMS remains the fallback when iMessage is unavailable.
How delivery differs
iMessage uses data and supports richer messaging behavior in the Apple ecosystem. SMS uses the carrier network and works more broadly across device types.
When fallback happens
If iMessage cannot send over data, the message may fall back to SMS depending on device settings. That fallback can change media quality and feature behavior.
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