XF 2.2 Changing the database collation to the MySQL 8.0 default "utf8mb4_0900_ai_ci"


Well-known member
By default, XenForo uses the MySQL collation "utf8mb4_general_ci" which is supported not only by MySQL 8.0 but by older MySQL versions like 5.7, too. In MySQL 8.0, the new collation "utf8mb4_0900_ai_ci" became the default. It is more modern and has better performance.

Since "utf8mb4_0900_ai_ci" is accent-insensitive ("ai"), some usernames that are considered to be different in "utf8mb4_general_ci" are considered to be equal in "utf8mb4_0900_ai_ci" which means there will be collisions (e.g. "Andre" and "André") and that some usernames would have to be changed when making the transition.

Should I expect something else to break / need attention?

(MySQL 8.0 also has an accent-sensitive collation "utf8mb4_0900_as_ci" but I tend to think that it would reduce confusion among users if two usernames who only differ in the accents would be forbidden.)