diff --git a/src/ckdb.h b/src/ckdb.h
index 91734fd7..dce130ea 100644
--- a/src/ckdb.h
+++ b/src/ckdb.h
@@ -52,7 +52,7 @@
 
 #define DB_VLOCK "1"
 #define DB_VERSION "0.9.2"
-#define CKDB_VERSION DB_VERSION"-0.502"
+#define CKDB_VERSION DB_VERSION"-0.503"
 
 #define WHERE_FFL " - from %s %s() line %d"
 #define WHERE_FFL_HERE __FILE__, __func__, __LINE__
@@ -540,7 +540,8 @@ extern tv_t missing_secuser_max;
 typedef struct users {
 	int64_t userid;
 	char username[TXT_BIG+1];
-	// Anything in 'status' disables the account
+	char usertrim[TXT_BIG+1]; // Non DB field
+	// TODO: Anything in 'status' disables the account
 	char status[TXT_BIG+1];
 	char emailaddress[TXT_BIG+1];
 	tv_t joineddate;
@@ -1174,6 +1175,7 @@ extern PGconn *dbconnect();
 // ***
 
 extern char *safe_text(char *txt);
+extern void username_trim(USERS *users);
 
 extern void _txt_to_data(enum data_type typ, char *nam, char *fld, void *data, size_t siz, WHERE_FFL_ARGS);
 
diff --git a/src/ckdb_data.c b/src/ckdb_data.c
index 5c0ae560..9dcf4431 100644
--- a/src/ckdb_data.c
+++ b/src/ckdb_data.c
@@ -40,6 +40,33 @@ char *safe_text(char *txt)
 	return ret;
 }
 
+#define TRIM_IGNORE(ch) ((ch) == '_' || (ch) == '.' || (ch) == '-' || isspace(ch))
+
+void username_trim(USERS *users)
+{
+	char *front, *trail;
+
+	front = users->username;
+	while (*front && TRIM_IGNORE(*front))
+		front++;
+
+	STRNCPY(users->usertrim, front);
+
+	front = users->usertrim;
+	trail = front + strlen(front) - 1;
+	while (trail >= front) {
+		if (TRIM_IGNORE(*trail))
+			*(trail--) = '\0';
+		else
+			break;
+	}
+
+	while (trail >= front) {
+		*trail = tolower(*trail);
+		trail--;
+	}
+}
+
 void _txt_to_data(enum data_type typ, char *nam, char *fld, void *data, size_t siz, WHERE_FFL_ARGS)
 {
 	char *tmp;
diff --git a/src/ckdb_dbio.c b/src/ckdb_dbio.c
index cf4b23f4..414c9b4e 100644
--- a/src/ckdb_dbio.c
+++ b/src/ckdb_dbio.c
@@ -450,13 +450,13 @@ K_ITEM *users_add(PGconn *conn, char *username, char *emailaddress,
 	ExecStatusType rescode;
 	bool conned = false;
 	PGresult *res;
-	K_ITEM *item;
-	USERS *row;
+	K_ITEM *item, *u_item;
+	USERS *row, *users;
 	char *ins;
 	char tohash[64];
 	uint64_t hash;
 	__maybe_unused uint64_t tmp;
-	bool ok = false;
+	bool dup, ok = false;
 	char *params[8 + HISTORYDATECOUNT];
 	int n, par = 0;
 
@@ -468,14 +468,30 @@ K_ITEM *users_add(PGconn *conn, char *username, char *emailaddress,
 
 	DATA_USERS(row, item);
 
+	STRNCPY(row->username, username);
+	username_trim(row);
+
+	dup = false;
+	K_RLOCK(users_free);
+	u_item = users_store->head;
+	while (u_item) {
+		DATA_USERS(users, u_item);
+		if (strcmp(row->usertrim, users->usertrim) == 0) {
+			dup = true;
+			break;
+		}
+		u_item = u_item->next;
+	}
+	K_RUNLOCK(users_free);
+
+	if (dup)
+		goto unitem;
+
 	row->userid = nextid(conn, "userid", (int64_t)(666 + (random() % 334)),
 				cd, by, code, inet);
 	if (row->userid == 0)
 		goto unitem;
 
-	// TODO: pre-check the username exists? (to save finding out via a DB error)
-
-	STRNCPY(row->username, username);
 	row->status[0] = '\0';
 	STRNCPY(row->emailaddress, emailaddress);
 
@@ -644,6 +660,8 @@ bool users_fill(PGconn *conn)
 		if (!ok)
 			break;
 
+		username_trim(row);
+
 		users_root = add_to_ktree(users_root, item, cmp_users);
 		userid_root = add_to_ktree(userid_root, item, cmp_userid);
 		k_add_head(users_store, item);