Macros

Some aspects of the library can be configured by defining preprocessor macros before including the json.hpp header. See also the macro overview page.

Runtime assertions

• JSON_ASSERT(x) - control behavior of runtime assertions

Exceptions

• JSON_CATCH_USER(exception)
  JSON_THROW_USER(exception)
  JSON_TRY_USER - control exceptions
• JSON_DIAGNOSTICS - control extended diagnostics
• JSON_DIAGNOSTIC_POSITIONS - access positions of elements
• JSON_NOEXCEPTION - switch off exceptions

Language support

• JSON_HAS_CPP_11
  JSON_HAS_CPP_14
  JSON_HAS_CPP_17
  JSON_HAS_CPP_20 - set supported C++ standard
• JSON_HAS_FILESYSTEM
  JSON_HAS_EXPERIMENTAL_FILESYSTEM - control std::filesystem support
• JSON_HAS_RANGES - control std::ranges support
• JSON_HAS_STD_FORMAT - control std::format/std::formatter support
• JSON_HAS_THREE_WAY_COMPARISON - control 3-way comparison support
• JSON_NO_IO - switch off functions relying on certain C++ I/O headers
• JSON_SKIP_UNSUPPORTED_COMPILER_CHECK - do not warn about unsupported compilers
• JSON_USE_GLOBAL_UDLS - place user-defined string literals (UDLs) into the global namespace

Library version

• JSON_SKIP_LIBRARY_VERSION_CHECK - skip library version check
• NLOHMANN_JSON_VERSION_MAJOR
  NLOHMANN_JSON_VERSION_MINOR
  NLOHMANN_JSON_VERSION_PATCH
  • library version information

Library namespace

• NLOHMANN_JSON_NAMESPACE - full name of the nlohmann namespace
• NLOHMANN_JSON_NAMESPACE_BEGIN
  NLOHMANN_JSON_NAMESPACE_END - open and close the library namespace
• NLOHMANN_JSON_NAMESPACE_NO_VERSION - disable the version component of the inline namespace

Type conversions

• JSON_BRACE_INIT_COPY_SEMANTICS - opt in to copy/move semantics for single-element brace initialization
• JSON_DISABLE_ENUM_SERIALIZATION - switch off default serialization/deserialization functions for enums
• JSON_USE_IMPLICIT_CONVERSIONS - control implicit conversions

Comparison behavior

• JSON_USE_LEGACY_DISCARDED_VALUE_COMPARISON - control comparison of discarded values

Serialization/deserialization macros

Enums

• NLOHMANN_JSON_SERIALIZE_ENUM - serialize/deserialize an enum
• NLOHMANN_JSON_SERIALIZE_ENUM_STRICT - serialize/deserialize an enum with exceptions

Classes and structs

• NLOHMANN_DEFINE_TYPE_INTRUSIVE - serialize/deserialize a non-derived class with private members
• NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT - serialize/deserialize a non-derived class with private members; uses default values
• NLOHMANN_DEFINE_TYPE_INTRUSIVE_ONLY_SERIALIZE - serialize a non-derived class with private members
• NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE - serialize/deserialize a non-derived class
• NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT - serialize/deserialize a non-derived class; uses default values
• NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE - serialize a non-derived class
• NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE - serialize/deserialize a derived class with private members
• NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_WITH_DEFAULT - serialize/deserialize a derived class with private members; uses default values
• NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_ONLY_SERIALIZE - serialize a derived class with private members
• NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE - serialize/deserialize a derived class
• NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_WITH_DEFAULT - serialize/deserialize a derived class; uses default values
• NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE - serialize a derived class
• NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_NAMES - serialize/deserialize a non-derived class with private members; uses custom names
• NLOHMANN_DEFINE_TYPE_INTRUSIVE_WITH_DEFAULT_WITH_NAMES - serialize/deserialize a non-derived class with private members; uses default values; uses custom names
• NLOHMANN_DEFINE_TYPE_INTRUSIVE_ONLY_SERIALIZE_WITH_NAMES - serialize a non-derived class with private members; uses custom names
• NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_NAMES - serialize/deserialize a non-derived class; uses custom names
• NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_WITH_DEFAULT_WITH_NAMES - serialize/deserialize a non-derived class; uses default values; uses custom names
• NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE_WITH_NAMES - serialize a non-derived class; uses custom names
• NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_WITH_NAMES - serialize/deserialize a derived class with private members; uses custom names
• NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_WITH_DEFAULT_WITH_NAMES - serialize/deserialize a derived class with private members; uses default values; uses custom names
• NLOHMANN_DEFINE_DERIVED_TYPE_INTRUSIVE_ONLY_SERIALIZE_WITH_NAMES - serialize a derived class with private members; uses custom names
• NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_WITH_NAMES - serialize/deserialize a derived class; uses custom names
• NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_WITH_DEFAULT_WITH_NAMES - serialize/deserialize a derived class; uses default values; uses custom names
• NLOHMANN_DEFINE_DERIVED_TYPE_NON_INTRUSIVE_ONLY_SERIALIZE_WITH_NAMES - serialize a derived class; uses custom names