The GSM Character Set: Everything You Need to Know

2 minute read

Team Upland

What is the GSM character set?

GSM, or Global System for Mobile Communications, refers to the alphabet used to write SMS messages.

How long can a standard SMS be using the GSM character set?

You can add up to 160 characters into a standard SMS, all of which must be part of a 7-bit default alphabet defined by GSM 3.38. This alphabet includes all the ASCII characters and some accented characters. For example, for our French-speaking audience, e with grave (è) or for our Spanish-speaking audiences, n with tilde (ñ)

Characters outside of this set are treated as a Unicode SMS. Unicode SMS limits the length of the SMS to 70 characters, for a single message, because of the different character encoding.

Once the number of characters exceeds the 160 or 70-character limit then the messages are split into smaller packages; these are the number of parts of a message. Each number of parts is equivalent to a credit. Below are the number of parts per character:

GSM SMS (Standard SMS)

GSM SMS (Standard SMS)

Unicode SMS (International SMS)

Unicode SMS (International SMS)

Common characters to avoid

There are some familiar characters you should avoid using and instead use their more efficient GSM counterparts.

GSM equivalent characters

GSM 03.38 7-bit character set

GSM 03.38 7-bit character set

The Extended GSM character set

You can send some additional characters using the <ESC> (0x1B) code in the above table, plus an extra character. These additional characters, known as the Extended GSM character set, require two standard GSM characters for each extended GSM character because they use the escape character prefix.

Some characters might not display correctly

This is because of handset limitations.

The Extended GSM character set

The unicode character set

The Unicode standard is a character encoding system that allows you to send a much larger range of characters than the standard Latin characters found in the GSM character set. It also allows you to send technical symbols and emojis.

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