To limit the length of username to certain characters, you need to add the following code to your theme’s functions.php.
Note: These codes will be wiped out after theme update. So, you need to create a child theme and add the codes there. You can check out this easy Tutorial on Creating a Child Theme.
So, after creating your Child Theme, you can add these codes in the child theme’s function.php.
Note: You can enter any number instead of 15 and the entered number will be the maximum character length.
// Username limit character length. add_action( 'user_registration_validate_user_login', 'ur_validate_user_login_field', 10, 4 ); function ur_validate_user_login_field( $single_form_field, $data, $filter_hook, $form_id ) { $field_label = isset( $data->label ) ? $data->label : ''; $username = isset( $data->value ) ? $data->value : ''; if ( 15 < strlen( $username ) ) { add_filter( $filter_hook, function ( $msg ) use ( $field_label ) { return __( $field_label . ' cannot exceed 15 characters.', 'user-registration' ); } ); } }
After you have pasted the code, users will only be able to enter the username of the defined length.
Please visit this URL to add the custom codes in your site.