SMS messages are transmitted in segments. A single segment holds up to
160 characters using standard GSM-7 encoding. When a message
exceeds that length, it is split into multiple segments and reassembled on the recipient's
device as one message.
- Single segment: up to 160 GSM-7 characters.
- Multi-segment: longer messages are divided into multiple segments. Because
each segment carries a small amount of overhead for reassembly, multi-segment messages hold
slightly fewer characters per segment than a standalone 160-character message.
- Headers count toward the total. Any text in the message header is included
in the character count.
On the Compose screen, the counter beneath the message box
shows Header, Content, Total, and
Max characters. For accounts with longer-message support enabled, the
Max value reflects the multi-segment limit (for example, 459
characters across three segments) and an additional counter tracks the number of segments.
- Each segment is billed individually. A message that spans three segments
costs three times a single-segment message. Keep messages concise to control costs.
- Aim for 160 characters or fewer, including the header.
- Avoid characters outside the GSM-7 set (certain emoji and special symbols force
Unicode encoding, which reduces the per-segment limit to about 70 characters).
- Use links and abbreviations to shorten content.
Note: Longer-message (multi-segment) support is an account-level
setting. If your Compose screen caps messages at 160 characters and you need longer messages,
contact TextCaster Support.