Unicode and its impact on SMS


What is Unicode text and how does it impact how to write SMS notifications?


  • All versions of xMatters
  • SMS Notifications


Unicode is an international standard that defines how text is represented in software.  This standard has evolved over time to allow the representation of most alphabets, punctuation, and symbols currently in use today.  Unicode is used in all major operating systems, browsers, search engines, laptops, smartphones, and across the internet.

To promote efficiency, SMS standards have defined a default character set based on Unicode.  This is necessary as standard SMS messages are limited to 160 characters per message. Longer messages are split into multiple segments, each delivered independently to the end user's phone.

Using the default character set is the most efficient method of writing SMS messages.  This is due to default characters being represented as one SMS character within the 160-character limit.

SMS Default Characters:

@ £ $ ¥ è é ù ì ò Ç Ø ø Å å Δ _ Φ Γ Λ Ω Π Ψ Σ Θ Ξ ^ { } \ [ ~ ] | € Æ æ ß É ! " # % & ' ( ) * + , - . / 0 1 2 3 4 5 6 7 8 9 : ; < = > ? A B C D E F G H I J K L M N O P Q R S T U V W X Y Z Ä Ö Ñ Ü § ¿ a b c d e f g h I j k l m n o p q r s t u v x y z ä ö ñ ü à [Space] [Line Feed] [Return]


"The quick brown fox jumps over the lazy dog", equals 44 characters within the 160-character message limit (spaces are counted as characters). 

Replacing the 'a' with acute: 'á' in the sentence above will change the character count and impose a 70-character message limit.

This occurs due to different encoding required to represent the 'á' which is not part of the default character set.

How does this impact message delivery?

xMatters will forward your message as written, however;

  • Carriers may replace non-default characters with alternates based on their own criteria.
  • Messages may be truncated or subject to additional length and segment limitations.
  • Message delivery may be inconsistent.
  • Some carriers may drop the message entirely.

Suggested Best Practice

xMatters will attempt to advise of country or carrier limitations, however, these can change without notice, or we may not be aware of the limitations. 

We suggest following these best practices:

  • Write your messages directly in xMatters or use a plain text editor.
  • Avoid the use of cut and paste from word processors or other apps as they may introduce hidden special characters.
  • Keep SMS messages short and limit your message to SMS default characters.
  • If you are sending long notifications or using special characters consider troubleshooting by reducing message length and removing special characters.


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