In many languages, such as English or French, there are few enough characters that make up the language that each letter (A, B, C) and number (1, 2, 3) can be represented by a single byte character set. In such a character set, each character is represented by an 8 bit byte. At most, 256 characters can be represented in a single-byte set.

The limit of 256 characters is not sufficient for many languages such as Japanese or Taiwanese. In cases such as these, a double byte character set is necessary to represent the large number of characters that make up the language. In a few languages even double-byte character sets are not sufficient in which case a multi-byte character set is used.

OpenX supports multi-byte character sets in SQL queries and comparisons and SQL variables.