Concatenated SMS
What is Concatenated SMS?
Concatenated SMS (also called multipart or long SMS) is the mechanism that lets a message longer than a single SMS segment's character limit be split into multiple linked segments, sent separately over the network, and reassembled into one message on the recipient's handset. Each additional segment consumes another billable message credit, and encoding matters: GSM-7 segments hold up to 153 characters when concatenated, while Unicode (UCS-2) segments — needed for emoji or non-Latin scripts — hold only 67.
More detail
A single (non-concatenated) GSM-7 segment holds up to 160 characters; once a message needs to split, each segment's usable length drops slightly to make room for the concatenation header.
Handsets reassemble concatenated segments transparently into one message, but if any single segment is delayed or dropped, the recipient may briefly see an incomplete message or none at all.
Frequently asked
- Why did my 200-character SMS get billed as two messages?
- Any message longer than a single segment's limit (160 GSM-7 characters, or 70 Unicode characters) is split into concatenated parts, and each part is billed as a separate message segment.
- Why does adding an emoji shrink how much text fits per message?
- An emoji forces the whole message into Unicode (UCS-2) encoding, which uses more bits per character than GSM-7, cutting the per-segment character limit from 160 down to 70 (67 when concatenated).
See also
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