Protocol Selection

The Linq API sends messages over iMessage, RCS, and SMS. See the Create Chat API reference for the full specification.

Every send uses the richest protocol the recipient supports, in the order iMessage → RCS → SMS. The service field on the message and its webhooks reports the protocol used for delivery.

Not all features are available on every protocol:

Feature	iMessage	RCS	SMS
Text messages	Yes	Yes	Yes
Images & video	Yes	Yes	MMS
Read receipts	Yes	Yes	No
Delivery receipts	Yes	Yes	No
Typing indicators	Yes	No	No
Reactions / tapbacks	Yes	Yes	No
Message effects	Yes	No	No
Group chats	Yes	Yes	MMS
Message threading	Yes	No	No
Rich link previews	Yes	Yes	No
Voice memos	Yes	Yes	No
File attachments (100MB)	Yes	Limited	No
Text decorations	Yes	No	No
Location sharing	Yes	No	No

To decide whether to use an iMessage-only feature such as message effects or text decorations, check the recipient first with the capability endpoints. See Capability Checks.