Features

This section describes the features of the library in detail. If you are new to the library, the pages below are roughly ordered along a typical workflow: create or parse a value, access and modify it, convert it to and from your own C++ types, and finally serialize it again.

Creating and reading values

• Creating JSON values — build values from literals, initializer lists, and STL containers, and understand the #!cpp {} vs. #!cpp [] ambiguity.
• Parsing — read a JSON value from a string, file, or stream, including JSON Lines, callbacks, the SAX interface, and error handling.
• Comments and trailing commas — opt-in relaxations of the JSON grammar.

Accessing and modifying values

• Element access — unchecked (operator[]), checked (at), and access with a default value.
• JSON Pointer — address values deep inside a document with RFC 6901 pointers.
• Iterators — traverse arrays and objects.
• Modifying values — add, update, merge, and remove elements.
• JSON Patch and Diff and JSON Merge Patch — apply and compute structured changes.

Converting to and from C++ types

• Converting values — get values out with get/get_to, and understand implicit conversions.
• Arbitrary types conversions — teach the library about your own structs and classes.
• Specializing enum conversion — map enums to strings instead of integers.

Serializing values

• Serialization — turn a value back into JSON text with dump, including pretty-printing and handling of non-ASCII and invalid UTF-8.
• Binary formats — encode values more compactly as BJData, BSON, CBOR, MessagePack, or UBJSON.
• Binary values — store and exchange raw byte sequences.

How values are stored and configured

• Types and number handling — how JSON types map to C++ types and how numbers are treated.
• Object order — keep insertion order with ordered_json.
• Runtime assertions, supported macros, the nlohmann namespace, and C++ modules — build-time and runtime configuration.

!!! tip “Looking for a specific function?”

This section gives conceptual overviews. For the precise signature, parameters, and return value of a function, see
the [API Documentation](../api/basic_json/index.md).