nlohmann/json

Health v2 · maintenance only

Adoption not part of the score

50656 stars · 7505 forks observed · 2026-09-23

What it is AI-extracted, prompt v1, taxonomy v1, 2026-09-21, confidence 0.97

nlohmann/json is a header‑only C++ library that provides a simple, modern API for parsing, generating, and manipulating JSON data. It also supports binary JSON formats like CBOR, MessagePack, BSON, and UBJSON.

Use cases

• Parse JSON strings or files into C++ objects
• Serialize C++ structs and STL containers to JSON
• Use JSON Pointer to access deep values in a document
• Apply JSON Patch or Merge Patch to modify JSON data
• Encode JSON data to compact binary formats such as CBOR or MessagePack
• Convert custom C++ types to/from JSON with to_json/from_json overloads
• Read and write JSON Lines streams for log processing

When to choose

• You need a lightweight, header‑only solution that works with modern C++ (C++11/14/17).
• Your project requires easy integration with STL containers and custom types.
• You want built‑in support for JSON Pointer, Patch, and several binary JSON formats.
• Cross‑platform compatibility (Linux, macOS, Windows) without external dependencies is important.

When to avoid

• You need runtime reflection or code generation for JSON binding beyond simple overloads.
• Maximum performance is critical and a hand‑optimized parser is required.
• You are working in a language other than C++ or need a non‑header‑only library.

Facets

library · maturity active

serialization parser json web-development backend cpp cross-platform modern-cpp header-only c++17 json-pointer json-patch binary-serialization binary-formats data-engineering

Member repositories

For agents

markdown · JSON · MCP: product_card(name="nlohmann/json")