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NOTE: libfastjson is a fork from json-c, and is currently under development.

The aim of this project is not to provide a slightly modified clone of json-c. It's aim is to provide

  • a small library with essential json handling functions
  • sufficiently good json support (not 100% standards compliant)
  • be very fast in processing

In order to reach these goals, we reduce the features of json-c. For similarities and differences, see the file DIFFERENCES.

IMPORTANT The current API is not stable and will change until version 1.0.0 is reached. We plan to reach it by summer 2016 at latest. With 1.0.0, the API will be stable. Until then, everything may change. Of course, we will not deliberatly break things but we need freedom to restructure.

Building on Unix with git, gcc and autotools


  • gcc, clang, or another C compiler
  • libtool

If you're not using a release tarball, you'll also need:

  • autoconf (autoreconf)
  • automake

Make sure you have a complete libtool install, including libtoolize.

libfastjson GitHub repo:

$ git clone
$ cd libfastjson
$ sh

followed by

$ ./configure
$ make
$ make install

To build and run the test programs:

$ make check

Linking to libfastjson

If your system has pkgconfig, then you can just add this to your makefile:

CFLAGS += $(shell pkg-config --cflags libfastjson)
LDFLAGS += $(shell pkg-config --libs libfastjson)

Without pkgconfig, you would do something like this:

CFLAGS += -I$(LIBFASTJSON_DIR)/include/libfastjson
LDFLAGS+= -L$(LIBFASTJSON_DIR)/lib -lfastjson