---
title: "UCS-2 encoding"
description: "UCS-2 is the 16-bit character encoding SMS uses for text outside the GSM-7 alphabet, such as Arabic, Chinese or emoji. One SMS holds 70 UCS-2 characters, or 67 per segment in a multipart message."
canonical: "https://omnichannels.ai/glossary/ucs-2/"
language: "en"
updated: "2026-10-10"
publisher: "BroadNet Technologies"
brand: "OmniChannels.ai"
---

# UCS-2 encoding

Canonical: https://omnichannels.ai/glossary/ucs-2/
Language: en
Publisher: OmniChannels.ai by BroadNet Technologies

**Definition:** UCS-2 is the 16-bit character encoding SMS uses for text outside the GSM-7 alphabet, such as Arabic, Chinese or emoji. One SMS holds 70 UCS-2 characters, or 67 per segment in a multipart message.

3GPP TS 23.038 states that UCS-2 coded user data can consist of up to 140 octets, that is up to 70 characters. In SMPP v3.4, UCS-2 is signalled with data_coding = 0x08.

When a long message is split, the 6-octet user data header leaves 134 octets per segment, or 67 UCS-2 characters.

UCS-2 can only represent characters in the Basic Multilingual Plane. Most emoji lie outside it and are sent as UTF-16 surrogate pairs, so each emoji uses two of the 70 slots. Handsets display them correctly, but they consume more space.

For Arabic-speaking markets in the GCC, UCS-2 is the normal encoding for Arabic text. Budget for shorter messages and more segments than an equivalent English message.

## Example

```
An Arabic OTP of 60 characters fits in 1 SMS; a 140-character Arabic message needs 3 segments (67 + 67 + 6).
```

## Sources

- [3GPP TS 23.038 — Alphabets and language-specific information](https://portal.3gpp.org/desktopmodules/Specifications/SpecificationDetails.aspx?specificationId=745)
- [SMPP Protocol Specification v3.4 (Issue 1.2) — SMPP.org](https://smpp.org/SMPP_v3_4_Issue1_2.pdf)