UTF8MB4

UTF8MB4, commonly written as utf8mb4, is a MySQL character set that encodes Unicode text using up to four bytes per character. It implements the full UTF-8 encoding, capable of representing all Unicode code points from U+0000 to U+10FFFF. This includes emoji and other characters outside the older three-byte range.

Historically, MySQL offered a utf8 character set that was limited to three bytes per character and could not store all supplementary Unicode characters. utf8mb4 was introduced to provide complete UTF-8 support and is now the recommended choice for new schemas and applications that handle diverse text. In practical terms, utf8mb4 stores data the same way as standard UTF-8, but can encode four-byte code points when needed.

Technical notes: utf8mb4 uses 1 to 4 bytes per character and is compatible with standard UTF-8 semantics. Sorting and comparisons are governed by collations, such as utf8mb4_general_ci and utf8mb4_unicode_ci, which determine case folding and ordering. Because characters may occupy up to four bytes, the maximum number of characters that can fit in a VARCHAR or TEXT column is smaller than with shorter encodings, and index length limitations can be affected. Some MySQL deployments require attention to index prefixes and storage settings when using utf8mb4.

Usage considerations: For new databases, utf8mb4 should be the default character set. When migrating from utf8, schema and data migrations are needed to avoid truncation or data loss, and client connections should be configured to use utf8mb4. Many programming languages and database drivers support utf8mb4, so updating application configurations helps ensure consistent text handling across environments.