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MySQL 5.4 Reference Manual :: 9 Internationalization and Localization :: 9.1 Character Set Support :: 9.1.10 Unicode Support :: 9.1.10.2 The utf8 Character Set (Three-Byte UTF-8 Unicode Encoding)
9.1.11 UTF-8 for Metadata »
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9.1.10.2. The utf8 Character Set (Three-Byte UTF-8 Unicode Encoding)

UTF-8 (Unicode Transformation Format with 8-bit units) is an alternative way to store Unicode data. It is implemented according to RFC 3629, which describes encoding sequences that take from one to four bytes. Currently, MySQL support for UTF-8 does not include four-byte sequences. (An older standard for UTF-8 encoding, RFC 2279, describes UTF-8 sequences that take from one to six bytes. RFC 3629 renders RFC 2279 obsolete; for this reason, sequences with five and six bytes are no longer used.)

The idea of UTF-8 is that various Unicode characters are encoded using byte sequences of different lengths:

  • Basic Latin letters, digits, and punctuation signs use one byte.

  • Most European and Middle East script letters fit into a two-byte sequence: extended Latin letters (with tilde, macron, acute, grave and other accents), Cyrillic, Greek, Armenian, Hebrew, Arabic, Syriac, and others.

  • Korean, Chinese, and Japanese ideographs use three-byte sequences.

Tip: To save space with UTF-8, use VARCHAR instead of CHAR. Otherwise, MySQL must reserve three bytes for each character in a CHAR CHARACTER SET utf8 column because that is the maximum possible length. For example, MySQL must reserve 30 bytes for a CHAR(10) CHARACTER SET utf8 column.