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JSON to C++ Converter

Free online JSON to C++ converter - Support nlohmann/json, RapidJSON, Boost.JSON

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How to Convert JSON to C++ Code Online

  1. 1

    Paste JSON

    Copy and paste your JSON data into the input box on the left.

  2. 2

    Select C++ Library

    Choose the target library in the configuration options: nlohmann/json (recommended), RapidJSON, or Boost.JSON.

  3. 3

    Configure Options

    Select C++ standard (C++11/14/17/20), naming style, indentation method, namespace, and more.

  4. 4

    Copy Result

    C++ code is generated in real-time on the right side. Click copy or download to use it in your project.

Features Overview

Free online JSON to C++ struct/class generator. Automatically generate C++ code from JSON data, supporting multiple libraries such as nlohmann/json, RapidJSON, Boost.JSON, compatible with C++11/14/17/20 standards.

Tool Description

Free online JSON to C++ converter. Automatically generates C++ struct/class code, supporting nlohmann/json, RapidJSON, Boost.JSON and other libraries. Compatible with C++11/14/17/20 standards, supports custom naming styles, indentation, and namespaces. Provides Unreal Engine integration examples. 100% browser-side processing, no data uploads.

Capabilities Checklist

  • Convert JSON to C++ struct/class in real-time with instant preview.
  • Support for multiple C++ JSON libraries: nlohmann/json (recommended), RapidJSON, Boost.JSON.
  • Support for C++11/14/17/20 standards with automatic generation of corresponding includes and syntax.
  • Flexible naming styles: camelCase or snake_case.
  • Customizable indentation (2 spaces/4 spaces/Tab), namespace, and struct names.
  • Automatic handling of nested objects, arrays, basic types, and mixed data structures.
  • Generate nlohmann/json serialization functions (NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE).
  • Support code comments and Unreal Engine integration examples.

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Frequently Asked Questions

How do I convert JSON to C++ code?
Paste your JSON data into the input box, and the tool will automatically generate C++ struct code with correct field types (std::string, int, double, bool, std::vector, etc.). You can then copy or download the result.
What is nlohmann/json?
nlohmann/json is a modern, easy-to-use C++ JSON library that provides a single header file implementation and supports C++11 and above. It is currently the most popular C++ JSON library with 40k+ stars on GitHub. This tool recommends it by default.
How do I use the generated code in Unreal Engine?
Select the "Unreal Engine" code snippet preset, and the tool will generate code with Unreal integration examples. You need to include the nlohmann/json library in your project, then integrate it into your C++ classes following the example code.
What is the difference between RapidJSON and nlohmann/json?
nlohmann/json is easier to use and provides an intuitive API; RapidJSON has higher performance and is suitable for handling large JSON files. Boost.JSON is a standard library integration solution. Which library to choose depends on your project requirements.
Which C++ standards does the generated code support?
The tool supports C++11, C++14, C++17, and C++20. Choosing different standards will affect the generated syntax (such as std::optional, constexpr, etc.). It is recommended to choose a standard consistent with your project.
What is the purpose of naming style?
Naming style determines the format of generated C++ field names. camelCase is a common style in C++; snake_case is suitable for certain project conventions. The tool automatically converts JSON key names.
How are nested JSON objects handled?
Nested JSON objects are converted to nested structs. For example, {"address": {"city": "Beijing"}} generates code containing an Address struct. There is no limit to nesting depth.
How are JSON arrays handled?
JSON arrays are converted to std::vector<T> type. Element type is inferred from the first non-null element. Object arrays generate corresponding struct types. Empty arrays default to std::vector<std::string>.
How do I add a namespace?
Enter your namespace name (such as MyApp) in the "Namespace" option. The generated code will automatically be wrapped in namespace MyApp { ... }.
Can the generated code be used directly?
Yes. The generated code includes complete struct definitions and necessary include statements. For nlohmann/json, it also includes serialization functions. You can copy it directly into your project.
Does this tool upload my data to a server?
No. All conversion processes are completed locally in your browser, and your JSON data will not be sent to any server. This ensures complete privacy of your code and data.