Are you using MySQL’s utf8 charset in your databases? In this write-up I’ll explain why you should switch to utf8mb4 instead, and how to do it.
UTF-8
The UTF-8 encoding can represent every symbol in the Unicode character set, which ranges from U+000000 to U+10FFFF. That’s 1,114,112 possible symbols. (Not all of these Unicode code points have been assigned characters yet, but that doesn’t stop UTF-8 from being able to encode them.)
UTF-8 is a variable-width encoding; it encodes each symbol using one to four 8-bit bytes. Symbols with lower numerical code point values are encoded using fewer bytes. This way, UTF-8 is optimized for the common case where ASCII characters and other BMP symbols (whose code points range from U+000000 to U+00FFFF) are used — while still allowing astral symbols (whose code points range from U+010000 to U+10FFFF) to be stored.
MySQL’s utf8
For a long time, I was using MySQL’s utf8 charset for databases, tables, and columns, assuming it mapped to the UTF-8 encoding described above. By using utf8, I’d be able to store any symbol I want in my database — or so I thought.
While writing about JavaScript’s internal character encoding, I noticed that there was no way to insert the U+1D306 TETRAGRAM FOR CENTRE (