MySQL’s actual equivalent of utf-8 is a character set known as utf8mb4. You should never use utf-8 since this can lead to troubling inconsistencies when changing vendors. utf-8 still exists is for backward compatibility with previous versions of MySQL.

utf8mb4

Although in other programming languages utf-8 characters usually require 1 to 4 bytes to store, MySQL simply assumes all characters to be 3 bytes in utf8mb4. This means that some characters are omitted from MySQL’s version of utf-8.

Length limit

In MySQL, the key length limit is 1000 bytes. VARCHAR(500) would result in an error since MySQL will assume 500 x 3 = 1500 bytes. On the other hand, VARCHAR(300) is considered to be valid since we are still below the 1000 bytes limit.