Edit file File name : jms_serializer.yaml Content :jms_serializer: handlers: datetime: default_format: 'Y-m-d\TH:i:sO' # DATE_ISO8601 visitors: json_serialization: options: - JSON_UNESCAPED_SLASHES - JSON_PRESERVE_ZERO_FRACTION xml_serialization: format_output: '%kernel.debug%' metadata: warmup: paths: included: - "%kernel.root_dir%/Entity/" - "%kernel.root_dir%/API/Model/" excluded: [] property_naming: id: 'jms_serializer.identical_property_naming_strategy' Save