Changes in MySQL 8.0 Option/Parameter Old Default New Default server_id 0 1 log-slave-updates OFF ON expire_logs_days 0 30 master-info-repository FILE TABLE relay-log-info-repository FILE TABLE transaction-write-set- extraction OFF XXHASH64 slave_rows_search_algorithms INDEX_SCAN, TABLE_SCAN INDEX_SCAN, HASH_SCAN slave_pending_jobs_size_max 16M 128M gtid_executed_compression_period 1000 0 Group Replication changes group_replication_autorejoin_tries 0 3 group_replication_exit_state_action ABORT_SERVER READ_ONLY group_replication_member_expel_timeout 0 5 For more information about options or variables which have been added, see Option/Variable Changes for mysqld  8.0, in the  MySQL Server Version Reference . The following sections explain the changes to defaults and any impact they might have on your deployment. Server Defaults •The default value of the  character_set_server  system variable and command line option  -- character-set-server changed from  latin1  to  utf8mb4 . This is the server’s default character set. At this time, UTF8MB4 is the dominant character encoding for the web, and this change makes life easier for the vast majority of MySQL users. The upgrade from 5.7 to 8.0 does not change any character set for any existing database objects. But unless you specify  character_set_server  back to your previous default or explicitly set the character set then a new schema, table, or column by default uses utf8mb4 . We recommend you move to  utf8mb4  whenever possible. •The default value of the collation_server  system variable and command line argument  -- collation-server  changed from  latin1_swedish_ci  to  utf8mb4_0900_ai_ci . This is the server’s default collation, the ordering of characters in a character set. There is a link between collations and character sets as each character set comes with a list of possible collations. The upgrade from 5.7 to 8.0 does not change any collation for any existing database objects, but takes effect for new objects. •The default value of the  explicit_defaults_for_timestamp  system variable changed from  OFF (MySQL legacy behavior) to  ON  (SQL standard behavior). This option was originally introduced in 5.6 and was  OFF  in 5.6 and 5.7.  •The default value of the  optimizer_trace_max_mem_size  system variable changed from  16KB  to 1MB . The old default caused the optimizer trace to be truncated for any non-trivial query. This change ensures useful optimizer traces for most queries. •The default value of the  validate_password_check_user_name  system variable changed from OFF  to  ON . This means that when the  validate_password  plugin is enabled, by default it now rejects passwords that match the current session user name. •The autosize algorithm for the  back_log  system variable has changed. The value for autosize (-1) is now set to the value of  max_connections , which is bigger than the calculated by  50 279