C/C++ JSON parser/generator benchmark
MIT License

Native JSON Benchmark

Copyright(c) 2014-2016 Milo Yip (miloyip@gmail.com)

Build Status


This benchmark evaluates the conformance and performance of 41 open-source C/C++ libraries with JSON parsing/generation capabilities. Performance means speed, memory, and code size.

Performance should be concerned only if the results are correct. This benchmark also test the conformance of library towards the JSON standards (RFC7159, ECMA-404).

Performance of JSON parsing/generation may be critical for server-side applications, mobile/embedded systems, or any application that requires processing of large size or number of JSONs. Native (C/C++) libraries are important because they should provide the best possible performance, while other languages may create bindings of native libraries.

The results show that several performance measurements vary in large scale among libraries. For example, the parsing time can be over 100 times. These differences came from many factors, including design and implementation details. For example, memory allocation strategies, design of variant type for JSON, number-string conversions, etc.

This benchmark may be useful for optimizing existing libraries and developing new, high-performance libraries.


The original author (Milo Yip) of this benchmark is also the primary author of RapidJSON.

Although the development of benchmark is attempted to be as objective and fair as possible, every benchmarks have their drawbacks, and are limited to particular testing procedures, datasets and platforms. And also, this benchmark does not compare additional features that a library may support, or the user-friendliness of APIs, securities, cross-platform, etc. The author encourage users to benchmarks with their own data sets and platforms.

Benchmarks and Measurements


Benchmark Description
Parse Validation Use JSON_checker test suite to test whether the library can identify valid and invalid JSONs. (fail01.json is excluded as it is relaxed in RFC7159. fail18.json is excluded as depth of JSON is not specified.)
Parse Double 66 JSONs, each with a decimal value in an array, are parsed. The parsed double values are compared to the correct answer.
Parse String 9 JSONs, each with a string value in an array, are parsed. The parsed strings are compared to the correct answer.
Roundtrip 27 condensed JSONs are parsed and stringified. The results are compared to the original JSONs.


Benchmark Description
Parse Parse in-memory JSON into DOM (tree structure).
Stringify Serialize DOM into condensed JSON in memory.
Prettify Serialize DOM into prettified (with indentation and new lines) JSON in memory.
Statistics Traverse DOM and count the number of JSON types, total length of string, and total numbers of elements/members in array/objects.
Sax Round-trip Parse in-memory JSON into events and use events to generate JSON in memory.
Sax Statistics Parse in-memory JSON into events and use events to conduct the statistics.
Code size Executable size in byte. (Currently only support jsonstat program, which calls "Parse" and "Statistics" to print out statistics of a JSON file. )

All benchmarks contain the following measurements:

Measurement Description
Time Duration in millisecond
Memory Memory consumption in bytes for the result data structure.
MemoryPeak Peak memory consumption in bytes throughout the parsing process.
AllocCount Number of memory allocation (including malloc, realloc(), new et al.)


Currently 43 libraries are successfully benchmarked. They are listed in alphabetic order:

Library Language Version Notes
ArduinoJson C++ 5.6.6
Boost.JSON C++ 1.80.0
CAJUN C++ 2.0.3
C++ REST SDK C++11 v2.8.0 Need Boost on non-Windows platform. DOM strings must be UTF16 on Windows and UTF8 on non-Windows platform.
ccan/json C
cJSON C 1.5.0
Configuru C++ 2015-12-18 gcc/clang only
dropbox/json11 C++11
Facil.io C 0.5.3
FastJson C++ Not parsing number per se, so do it as post-process.
folly C++11 2016.08.29.00 Need installation
gason C++11
jansson C v2.7
jeayeson C++14
json-c C 0.12.1
jsoncons C++11 0.97.1
json-voorhees C++ v1.1.1
json spirit C++ 4.08 Need Boost
Json Box C++ 0.6.2
JsonCpp C++ 1.0.0
hjiang/JSON++ C++
jsmn C Not parsing number per se, so do it as post-process.
jvar C++ v1.0.0 gcc/clang only
Jzon C++ v2-1
nbsdx/SimpleJSON C++11
Nlohmann/json C++11 v2.0.3
parson C
picojson C++ 1.3.0
pjson C No numbers parsing, no DOM interface
POCO C++ 1.7.5 Need installation
qajson4c C 1.0.0 gcc/clang only
Qt C++ 5.6.1-1 Need installation
RapidJSON C++ v1.1.0 There are four configurations: RapidJSON (default), RapidJSON_AutoUTF (transcoding any UTF JSON), RapidJSON_Insitu (insitu parsing) & RapidJSON_FullPrec (full precision number parsing)
sajson C++
SimpleJSON C++
sheredom/json.h C Not parsing number per se, so do it as post-process.
udp/json C 1.1.0 Actually 2 libraries: udp/json-parser & udp/json-builder.
taocpp/json C++11 1.0.0-beta.7 Uses PEGTL for parsing
tunnuz/JSON++ C++
ujson C++ 2015-04-12
ujson4c C
V8 C++ Need installation
vincenthz/libjson C 0.8
YAJL C 2.1.0
ULib C++ v1.4.2 Need building: (./configure --disable-shared && make)

Libraries with Git repository are included as submodule in thirdparty path. Other libraries are add as files in thirdparty path.

The exact commit of submodule can be navigated at here.

To measure the overheads of the benchmark process, a strdup test is added for comparison. It simply allocate and copy the input string in Parse and Stringify benchmark.

Besides, some libraries was tried to integrated in this benchmark but failed:

Library Issue
libjson Unable to parse UTF-8 string
StiX Json
boost property_tree number, true, false, null types are converted into string.

JSON data

All tested JSON data are in UTF-8.

JSON file Size Description
canada.json source 2199KB Contour of Canada border in GeoJSON format. Contains a lot of real numbers.
citm_catalog.json source 1737KB A big benchmark file with indentation used in several Java JSON parser benchmarks.
twitter.json 632KB Search "δΈ€" (character of "one" in Japanese and Chinese) in Twitter public time line for gathering some tweets with CJK characters.

The benchmark program reads data/data.txt which contains file names of JSON to be tested.

Build and Run

  1. Execute git submodule update --init and git -C thirdparty/boost update --init to download all submodules (libraries).
  2. Obtain premake5.
  3. Copy premake5 executable to build/ path (or system path).
  4. Run premake.bat or premake.sh in build/
  5. On Windows, build the solution at build/vs2015/.
  6. On other platforms, run GNU make -f benchmark.make config=release_x32 && make -f nativejson.make config=release_x32 (or release_x64) at build/gmake/
  7. Optional: run build/machine.sh for UNIX or CYGWIN to use CPU info to generate prefix of result filename.
  8. Run the nativejson_release_... executable is generated at bin/
  9. The results in CSV format will be written to result/.
  10. Run GNU make in result/ to generate results in HTML.

For simplicity, on Linux/OSX users can simply run make (or make CONFIG=release_x32) at project root to run 4-10 above.

Some libraries, such as Boost, POCO, V8, etc., need to be installed by user manually.

Sample Results

Update on: 2016-9-9

A collection of benchmarks results can be viewed HERE. Select "Benchmark" from the menu to check available benchmark configurations. The presentation is powered by Google Charts with interactivity.

The followings are some snapshots from the results of MacBook Pro (Retina, 15-inch, Mid 2015, Corei7-4980HQ@2.80GHz) with clang 7.0 64-bit.



This is the average score of 4 conformance benchmarks. Higher is better. Details.

Parsing Time

Parsing Time

This is the total duration of parsing 3 JSONs to DOM representation, sorted in ascending order. Lower is better. Details

Parsing Memory

Parsing Memory

This is the total memory after parsing 3 JSONs to DOM representation, sorted in ascending order. Lower is better. Details

(Note: The results for Qt is incorrect as the benchmark failed to hook its memory allocations)

Stringify Time

Stringify Time

This is the total duration of stringifying 3 DOMs to JSONs, sorted in ascending order. Lower is better. Details

Prettify Time

Prettify Time

This is the total duration of prettifying 3 DOMs to JSONs, sorted in ascending order. Lower is better. Details

Code Size

Code Size

The is the size of executable program, which parses a JSON from stdin to a DOM and then computes the statistics of the DOM. Lower is better. Details


  1. How to add a library?

    Use submodule add https://...xxx.git thirdparty/xxx to add the libary's repository as a submobule. If that is not possible, just copy the files into 'thirdparty/xxx'.

    For C libary, add a xxx_all.c in src/cjsonlibs, which #include all the necessary .c files of the library. And then create a tests/xxxtest.cpp.it

    For C++ library, just need to create a tests/xxxtest.cpp, which #include all the necessary .cpp files of the library.

    You may find a existing library which similar to your case as a start of implementing tests/xxxtest.cpp.

    Please submit a pull request if the integration work properly.

  2. What if the build process is failed, or the benchmark crashes?

    This happens on some platforms as not every libaray is stable for all platforms.

    You can simply delete the local tests/xxxtest.cpp and re-run the build.

    BTW, if you are adding a library, you can remove all tests/xxxtest.cpp except tests/rapidjsontest.cpp and your test. This make the build process fast. RapidJSON's test is needed as a reference to compare statistics results only.

  3. On which platform the benchmark can be run?

    The author tests it on OSX/clang, Winwdows/vs2015, Ubuntu/clang3.7+gcc5.0 (via Travis CI). The benchmark may work in other platforms as well but you will need to generate the build files via premake5, and resolve any potential issues.

  4. How to reduce the build process time?

    You can preserve the tests of libaries that you only need, as in question 2. You can also use make ARGS=--verify-only, make ARGS=--performance-only, make ARGS=--conformance-only to execute the required part.

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