MariaDB sql_mode default differs per LTS line ; ALWAYS pin sql_mode explicitly in [mysqld] for production.
10.2.4+ default sql_mode : STRICT_TRANS_TABLES,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION. Same string applies to 10.6, 10.11, 11.x, 12.x stock builds.
utf8 is a 3-byte alias for utf8mb3. Use utf8mb4 for full Unicode (emoji, supplementary planes above U+FFFF).
TWO SEPARATE default changes : (A) the server default charset character_set_server flipped from latin1 to utf8mb4 in 11.6 ; (B) the default collation OF the utf8mb4 charset flipped from utf8mb4_general_ci to utf8mb4_uca1400_ai_ci one release earlier, in 11.5. Because the server charset stayed latin1 through 11.5, the effective collation_server only becomes utf8mb4_uca1400_ai_ci in 11.6 (when the server charset itself becomes utf8mb4). 10.6 LTS and 10.11 LTS stock builds still default to latin1 / latin1_swedish_ci. Debian / Ubuntu distro packages override to utf8mb4.
Default binlog_format is MIXED since 10.2.3 (NOT ROW).
Default sync_binlog=0 trades durability for write throughput ; set sync_binlog=1 for crash-safe binlog on a primary.
Default innodb_flush_log_at_trx_commit=1 (full ACID).
Default default_storage_engine=InnoDB since 10.2.
Default authentication plug-in is still mysql_native_password (SHA-1) ; ALWAYS choose ed25519 explicitly for new users (available since 10.1.21).
lower_case_table_names defaults : Linux 0, Windows 1, macOS 2. CANNOT be changed after mariadb-install-db.
sql_mode scope is session and global ONLY. There is NO per-database sql_mode.
Stored programs and views lock in the sql_mode value that was active at CREATE-time. Later global changes do NOT affect them.
ALWAYS run SELECT @@version, @@sql_mode, @@character_set_server, @@collation_server, @@binlog_format, @@sync_binlog; before declaring a config "the same as before".
NEVER edit /etc/my.cnf and assume the running server picked it up ; mysqld reads option files at startup only.

Default sql_mode by Version

Version range	Default sql_mode
10.1.6 and earlier	(empty)
10.1.7 to 10.2.3	`NO_ENGINE_SUBSTITUTION,NO_AUTO_CREATE_USER`
10.2.4 and later (incl. 10.6, 10.11, 11.x, 12.x)	`STRICT_TRANS_TABLES,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION`

Distro packages (Debian, Ubuntu, RHEL) sometimes ship overrides in /etc/mysql/mariadb.conf.d/*.cnf. ALWAYS verify with SELECT @@sql_mode; on the live instance.

Decision Tree : Setting sql_mode

Are you running a new production instance ?
- YES : pin sql_mode='STRICT_TRANS_TABLES,STRICT_ALL_TABLES,NO_ENGINE_SUBSTITUTION,NO_ZERO_DATE,NO_ZERO_IN_DATE,ERROR_FOR_DIVISION_BY_ZERO' in [mysqld].
- NO : continue.
Are you upgrading from MariaDB <= 10.1 ?
- YES : explicitly set sql_mode='' first, deploy, then enable strict modes one at a time after data validation. Stock 10.2.4+ default flips strict ON.
Are you migrating from MySQL 8 ?
- YES : copy the source @@sql_mode exactly (SELECT @@sql_mode on MySQL), pin it in MariaDB [mysqld], then plan to remove ONLY_FULL_GROUP_BY and NO_AUTO_VALUE_ON_ZERO only after auditing app code.
Do you need ANSI standard quoting ("col" as identifier) ?
- YES : set sql_mode='ANSI_QUOTES,...' GLOBALLY, never per-session, because stored programs capture sql_mode at CREATE time.

Decision Tree : Default Charset

Is the install fresh and < 11.6 ?

YES : ALWAYS set in [mysqld] :

character-set-server = utf8mb4
collation-server = utf8mb4_uca1400_ai_ci

Is the install 11.6+ ?
- YES : the stock default is already utf8mb4_uca1400_ai_ci. Still pin explicitly to survive future default-shifts.
Are you migrating an existing DB ?
- YES : convert per table with ALTER TABLE t CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_uca1400_ai_ci;. The server default only affects NEW tables, not existing ones.
Do you see Incorrect string value: '\xF0\x9F...' errors ?
- That is the emoji-in-utf8mb3 trap. The column is utf8 (3-byte), not utf8mb4. Convert the column.

SQL Mode Scope and Stored-Program Lock-In

sql_mode exists at TWO scopes only :

@@global.sql_mode : applied to every new connection at login time. Requires SUPER (or SET_USER_ID) privilege to change.
@@session.sql_mode : per-connection override, lasts until disconnect.

There is NO ALTER DATABASE ... SQL_MODE ... and NO per-table sql_mode. Anyone telling you otherwise is conflating MariaDB with another DBMS.

Stored procedures, functions, triggers, events, and views CAPTURE the current @@session.sql_mode value at CREATE time and lock it into the routine metadata. Subsequent SET GLOBAL sql_mode = ... does NOT change the routine's effective mode. To rotate a procedure's mode you MUST DROP and recreate with the desired session sql_mode active. Verify with :

SELECT routine_name, sql_mode
FROM information_schema.routines
WHERE routine_schema = DATABASE();

my.cnf Option-File Lookup

MariaDB mysqld reads option files at startup in this order on Linux (later files override earlier ones for the same option) :

/etc/my.cnf
/etc/mysql/my.cnf
$MYSQL_HOME/my.cnf (typically /var/lib/mysql/my.cnf or /usr/local/mysql/my.cnf)
The file named by --defaults-extra-file=<path> if passed on the command line
~/.my.cnf
~/.mylogin.cnf (obfuscated credentials for the mariadb client only)

Distro packages add an include directive in /etc/mysql/my.cnf :

!includedir /etc/mysql/mariadb.conf.d/
!includedir /etc/mysql/conf.d/

Files in those directories are read in alphabetical order. A 99-custom.cnf overrides a 50-server.cnf.

Section selection : [mysqld] for the server daemon, [mariadb] for MariaDB-specific options ignored by MySQL clients, [client] for every official client (mariadb, mariadb-dump, etc.), [mariadb-10.11] for version-specific overrides. The [server] group is read by all server-side programs.

ALWAYS reload (systemctl restart mariadb) after editing option files ; SET GLOBAL changes the running value but does NOT persist across restart unless ALSO written to the option file.

Default Variables That Bite on Upgrade

Variable	Default	Why it bites
`sql_mode`	`STRICT_TRANS_TABLES,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION` (10.2.4+)	Inserts that worked on 10.1 now fail with `Data too long`, `Incorrect string value`, `Out of range value`
`character_set_server`	`latin1` (< 11.6) / `utf8mb4` (11.6+)	Tables created without explicit CHARSET lock to latin1, breaking emoji
`collation_server`	`latin1_swedish_ci` (< 11.6) / `utf8mb4_uca1400_ai_ci` (11.6+)	Follows `character_set_server` ; the default collation of `utf8mb4` itself changed from `utf8mb4_general_ci` to `utf8mb4_uca1400_ai_ci` in 11.5. Cross-table JOIN raises `Illegal mix of collations`
`binlog_format`	`MIXED` (10.2.3+)	Statement-based subset can drift on non-deterministic UDFs ; row-based applies cleanly
`sync_binlog`	`0`	Crash-test reveals up to several seconds of binlog loss
`innodb_flush_log_at_trx_commit`	`1`	Setting `2` for throughput silently loses 1s on OS crash
`default_storage_engine`	`InnoDB` (10.2+)	A node configured `MyISAM` in `my.cnf` silently creates non-transactional tables
`lower_case_table_names`	Linux 0 / Win 1 / macOS 2	Linux-built dump restored on Windows server breaks on case-folded table names
`default_authentication_plugin`	`mysql_native_password`	New users get SHA-1 hashing ; clients with `caching_sha2_password` only refuse to connect

Production-Ready `my.cnf` Snippet

[mysqld]
# Locale and identifiers
character-set-server         = utf8mb4
collation-server             = utf8mb4_uca1400_ai_ci
sql_mode                     = STRICT_TRANS_TABLES,STRICT_ALL_TABLES,NO_ENGINE_SUBSTITUTION,NO_ZERO_DATE,NO_ZERO_IN_DATE,ERROR_FOR_DIVISION_BY_ZERO
default_storage_engine       = InnoDB
innodb_default_row_format    = dynamic

# Durability
sync_binlog                  = 1
innodb_flush_log_at_trx_commit = 1
innodb_doublewrite           = 1

# Binlog
log_bin                      = /var/log/mysql/mariadb-bin
binlog_format                = MIXED
expire_logs_days             = 14

# Auth
plugin_load_add              = auth_ed25519

[client]
default-character-set        = utf8mb4

When Defaults DO Change Within an LTS Line

LTS minor releases occasionally tighten defaults :

innodb_buffer_pool_chunk_size deprecated 10.11.12+.
slave_parallel_mode=optimistic default since 10.5.1+.
Semi-sync replication built-in (no plug-in install) since 10.3+.

ALWAYS read the release notes for the exact minor version you upgrade to. The LTS guarantee is API/feature stability, not zero-default-change.

Verification After Any Config Change

SELECT @@version, @@sql_mode, @@character_set_server, @@collation_server,
       @@binlog_format, @@sync_binlog, @@innodb_flush_log_at_trx_commit,
       @@default_storage_engine, @@lower_case_table_names;

Compare the result to your my.cnf snippet line-by-line. Drift between the file and the live value means another option file (later in the lookup order) or a SET GLOBAL from a previous session overrode it.

Reference Files

references/methods.md : full sql_mode flag table with version + impact ; charset / collation default matrix per LTS ; option-file section grammar ; system-variable scope semantics.
references/examples.md : 10+ working snippets covering pinning sql_mode, charset migration, procedure lock-in, sync_binlog crash-recovery, my.cnf inheritance.
references/anti-patterns.md : 8 production failure modes with WHY-it-fails and the corrected pattern.

Sources

MariaDB KB sql-mode : https://mariadb.com/docs/server/server-management/variables-and-modes/sql_mode
Character set overview : https://mariadb.com/kb/en/character-set-and-collation-overview/
Unicode / utf8 alias : https://mariadb.com/kb/en/unicode/
Replication and binary log variables : https://mariadb.com/kb/en/replication-and-binary-log-system-variables/
InnoDB system variables : https://mariadb.com/kb/en/innodb-system-variables/
ed25519 authentication : https://mariadb.com/kb/en/authentication-plugin-ed25519/
Identifier case sensitivity : https://mariadb.com/kb/en/identifier-case-sensitivity/
Binary log formats : https://mariadb.com/kb/en/binary-log-formats/

mariadb-core-defaults-and-sql-modes

MariaDB Defaults and SQL Modes

Quick Reference