# UCS-2 — Unicode SMS encoding explained

> UCS-2 is the 16-bit Unicode encoding used by SMS when the message body contains any character that is not in the GSM 7-bit alphabet. Arabic, Chinese, Cyrillic, Vietnamese, emoji, and curly quotes all force a message to UCS-2. The trade-off: a UCS-2 SMS carries only 70 characters per segment (vs 160 for GSM 7-bit) — so a 150-character Arabic message costs three billable segments where the same-length English message costs one.

- Canonical URL: https://www.broadnet.me/answers/what-is-ucs-2-sms
- Language: en
- Last reviewed: 2026-05-28
- Publisher: BroadNet (https://www.broadnet.me)

## What it actually does

An SMS submit_sm includes a data_coding field that tells the SMSC how to interpret the message body. DCS = 0x00 (or 0x01) means GSM 7-bit, the default 160-character encoding. DCS = 0x08 means UCS-2, two bytes per character. The SMSC propagates the data_coding to the recipient operator's SMSC, which propagates it to the handset; the handset displays the body using the indicated encoding. Mixing — sending a GSM-7-encoded body with a UCS-2 character in it — is a protocol violation and produces garbled display.

## Why it matters commercially

For MENA messaging, UCS-2 is the default — virtually all consumer-facing Arabic A2P traffic is UCS-2, and so each message costs 2-3 segments instead of 1. This is not optional; transliterating Arabic into Latin destroys consumer recognition and engagement. The mature operator practice is to pre-classify Arabic UCS-2 traffic at the SMSC and price it appropriately. For Latin-script markets, the optimisation is to scrub composition for accidental UCS-2 triggers (em-dashes, curly quotes, emoji from a marketer's Word document) before submit.

## Operational angle

Most aggregators auto-detect encoding from the submitted body and set data_coding accordingly. Some let you force the encoding (useful for testing). When debugging billing surprises ("why is my Arabic campaign costing 3x what I expected?"), the first thing to check is the data_coding distribution of the campaign — if you expected GSM-7 but the bodies are coming through as UCS-2, somebody added a curly quote.

## Privacy and compliance considerations

Encoding is metadata; it is not personal data on its own and is not in PDPL/GDPR scope. But UCS-2 is the encoding used for Arabic, which means UCS-2 traffic is statistically more likely to carry MENA-resident personal data. Operators in regulated MENA markets typically apply the strictest data-residency rules to UCS-2 traffic specifically, on the safe-default assumption that it carries local-language personal data.

## Related

- [All answers](https://www.broadnet.me/answers)
- [Glossary](https://www.broadnet.me/answers)
- [What is GSM-7 encoding?](https://www.broadnet.me/answers/what-is-gsm-7)
- [UDH — User Data Header in SMS explained](https://www.broadnet.me/answers/what-is-udh-sms)
- [GSM 7-bit vs UCS-2 encoding — when each is used](https://www.broadnet.me/answers/what-is-encoding-gsm-7-ucs-2)
- [SMS pricing per MT — what you're actually paying for](https://www.broadnet.me/answers/sms-pricing-per-mt-explained)
- [SMS segment calculator](https://www.broadnet.me/tools/sms-segment-calculator)
- [SMS API](https://www.broadnet.me/products/sms-api)
- [Bulk SMS](https://www.broadnet.me/products/bulk-sms)