JSON for Modern C++ vs TOML
Which should you use? A side-by-side look at what each one does, who it suits, what it costs, how hard it is to set up, and where each falls short.
Open source · MIT
A single-header C++ library for reading, writing and manipulating JSON data.
Open source · MIT
A minimal configuration file format meant to be easy to read and map to key-value data.
The short answer
Choose JSON for Modern C++ if you need…
- C++ developers who need to read or write JSON in an application
- Teams that want a library with no dependencies and a simple header-based setup
- Projects that prioritize ease of use over raw parsing speed
- Developers who want JSON Patch or JSON Pointer support in C++
Choose TOML if you need…
- Developers writing configuration files for an application or tool
- People who want comments and readable settings without YAML's complexity
- Projects that need a parser in their programming language of choice
- Anyone comparing config formats such as JSON, YAML, or INI
Side-by-side
| JSON for Modern C++ | TOML | |
|---|---|---|
| Type | Library | Other |
| Price | Free and open source | Free and open source |
| Licence | MIT | MIT |
| GitHub stars | 50.8k | 20.7k |
| Setup difficulty | Beginner | Beginner |
| How you get it | Clone and build from source | See the README |
| Main language | C++ | — |
| Last code update | 4 days ago | 6 days ago |
What each one is
JSON for Modern C++
nlohmann/json is a C++ library that lets programs work with JSON data using familiar C++ containers and operators, so JSON objects and arrays can be handled much like std::map and std::vector. It is distributed as a single header file, which makes it simple to add to a project. The README also mentions support for related formats such as CBOR, MessagePack and BSON, plus JSON Pointer and JSON Patch.
TOML
TOML is a specification for a plain-text file format used mainly for configuration settings. It aims to be easy to read because its rules are simple and obvious, and it maps unambiguously to a hash table so programs can load it into data structures. This repository holds the in-development version of the spec; released versions are published at toml.io.
Best for
JSON for Modern C++
- C++ developers who need to read or write JSON in an application
- Teams that want a library with no dependencies and a simple header-based setup
- Projects that prioritize ease of use over raw parsing speed
- Developers who want JSON Patch or JSON Pointer support in C++
TOML
- Developers writing configuration files for an application or tool
- People who want comments and readable settings without YAML's complexity
- Projects that need a parser in their programming language of choice
- Anyone comparing config formats such as JSON, YAML, or INI
Strengths
JSON for Modern C++
- Single header file with no dependencies, according to the README
- Intuitive syntax that feels close to native C++ containers
- Heavily unit-tested with fuzzing via Google OSS-Fuzz and MIT licensed
TOML
- Simple, readable syntax with comments, as described in the README
- Designed to map unambiguously to a hash table, which makes parsing predictable
- Open specification under the MIT license with a wiki cataloging implementations
Not ideal for
JSON for Modern C++
- Projects that need the fastest possible JSON parsing, since the README says faster libraries exist
- Developers not working in C++, because this library is for C++ only
- Projects that must avoid a large single header file in build times, as the README does not discuss compile-time cost
TOML
- Serializing arbitrary data: the README says TOML is not meant for that, and it does not allow top-level arrays or floats
- Streaming use cases that need a standard start or end marker, since the README notes no standard exists for this
- Readers looking for downloadable software: this repo is the language specification, not an application
Trade-offs
JSON for Modern C++
- The README says it is not the fastest JSON library available
- Documentation and examples are primarily hosted on an external site, so the README alone gives limited detail
- The README is truncated, so some features and setup details could not be verified here
TOML
- The README describes the repo as the in-development spec; released versions live at toml.io, so you may need to check which one applies
- Not designed as a general data serialization format, which limits some uses
- The README does not itself list parsers or tools; those are in the wiki
Getting started
JSON for Modern C++
Clone the repository
git clone https://github.com/nlohmann/json.gitFrequently asked questions
What is the difference between JSON for Modern C++ and TOML?
JSON for Modern C++: A single-header C++ library for reading, writing and manipulating JSON data. TOML: A minimal configuration file format meant to be easy to read and map to key-value data. JSON for Modern C++ suits c++ developers who need to read or write json in an application, while TOML suits developers writing configuration files for an application or tool.
Are JSON for Modern C++ and TOML free?
JSON for Modern C++: Free and open source. TOML: Free and open source.
Is JSON for Modern C++ or TOML more popular?
JSON for Modern C++ has more GitHub stars (50.8k) than TOML (20.7k). Popularity isn't the same as fit — check which one matches your use case above.
What are other alternatives to JSON for Modern C++ and TOML?
Other options people compare them with include SwiftyJSON, GJSON, cpp-httplib, EnTT.
Keep comparing
Built from our catalogue entries for both products: open-source details come from each project's README (AI-assisted, refreshed weekly) and GitHub data; AI-tool details are editorial. Spotted something wrong? Let us know from either product's page.