Skip to main content

Universal Binary JSON encoder/decoder

Project description


This is a Python v3.2+ (and 2.7+) Universal Binary JSON encoder/decoder based on the draft-12 specification.

Installing / packaging

# To get from PyPI
pip3 install py-ubjson

# To only build extension modules inline (e.g. in repository)
python3 build_ext -i

# To build & install globally
python3 install

# To skip building of extensions when installing (or building)
PYUBJSON_NO_EXTENSION=1 python3 install


  • The extension module is not required but provide a significant speed boost.
  • The above can also be run with v2.7+
  • This module is also available via Anaconda (conda-forge)
  • PyPI releases are signed with the Iotic Labs Software release signing key
  • At run time, one can check whether compiled version is in use via the ubjson.EXTENSION_ENABLED boolean


It's meant to behave very much like Python's built-in JSON module, e.g.:

import ubjson

encoded = ubjson.dumpb({u'a': 1})

decoded = ubjson.loadb(encoded)

Note: Only unicode strings in Python 2 will be encoded as strings, plain str will be encoded as a byte array.


import ubsjon

Command-line utility

This converts between JSON and UBJSON formats:

python3 -mubjson
USAGE: ubjson (fromjson|tojson) (INFILE|-) [OUTFILE]



This library has been checked using flake8 and pylint, using a modified configuration - see pylint.rc and flake8.cfg.


python3 -mvenv py
. py/bin/activate
pip install -U pip setuptools
pip install -e .[dev]


Note: See for additional requirements.


  • The No-Op type is only supported by the decoder. (This should arguably be a protocol-level rather than serialisation-level option.) Specifically, it is only allowed to occur at the start or between elements of a container and only inside un-typed containers. (In a typed container it is impossible to tell the difference between an encoded element and a No-Op.)
  • Strongly-typed containers are only supported by the decoder (apart from for bytes/bytearray) and not for No-Op.
  • Encoder/decoder extensions are not supported at this time.


The only existing implementation I was aware of at the time of writing (simpleubjson) had the following limitations:

  • Does not support efficient binary encoding
  • Only supports draft-9
  • Only supports individual Python types rather than anything implementing an interface (e.g. Mapping)
  • Does not decode nested arrays or objects in expected form
  • Lacks C extension speed-up

Download files

Download the file for your platform. If you're not sure which to choose, learn more about installing packages.

Source Distribution

py-ubjson-0.16.1.tar.gz (50.3 kB view hashes)

Uploaded source

Supported by

AWS AWS Cloud computing Datadog Datadog Monitoring Facebook / Instagram Facebook / Instagram PSF Sponsor Fastly Fastly CDN Google Google Object Storage and Download Analytics Huawei Huawei PSF Sponsor Microsoft Microsoft PSF Sponsor NVIDIA NVIDIA PSF Sponsor Pingdom Pingdom Monitoring Salesforce Salesforce PSF Sponsor Sentry Sentry Error logging StatusPage StatusPage Status page