---
id: py-ubjson
version: "0.16.1"
license: Apache License 2.0
license_treatment: permissive
maintenance: dormant
---

# py-ubjson — Universal Binary JSON encoder/decoder

License: permissive · Maintenance: dormant · Downloads: 1.5M/mo

## What it is and what it does

py-ubjson is an encoder and decoder for Universal Binary JSON, a compact binary serialization format defined by the UBJSON specification. It provides a Python API similar to the standard json module, with dump/load functions for file I/O and dumpb/loadb for bytes. The package includes an optional C extension that significantly accelerates encoding and decoding operations; you can check at runtime whether the compiled version is active via a boolean flag. It supports efficient binary encoding, nested structures, and typed containers according to the draft-12 specification.

The package has no runtime dependencies and can be installed with or without the C extension. It includes a command-line utility for converting between JSON and UBJSON formats. The implementation is stable (marked Production/Stable) but dormant, with the last release in April 2020 and minimal recent activity.

Use it for:

- Serialize structured data to a compact binary format for efficient network transmission or storage.
- Decode UBJSON data received from external systems or APIs that use the UBJSON standard.
- Replace JSON in performance-critical applications where binary encoding overhead matters.
- Convert between JSON and UBJSON formats via the command-line utility for data pipeline tasks.

## Worth the install?

AI-flagged interpretation of the facts above — verify before relying.

Encodes and decodes data in Universal Binary JSON format, a compact binary serialization standard, with optional C extension acceleration.

Yes, with conditions. The package is stable and permissively licensed, suitable for UBJSON serialization tasks. However, install friction is high due to optional C extension compilation, and dormant maintenance (last release 2020) means no recent bug fixes or Python version updates. Verify compatibility with your target Python version before adopting. Use it if you specifically need UBJSON support; for general binary serialization, consider actively maintained alternatives.

## Install

pip install py-ubjson
uv add py-ubjson
poetry add py-ubjson

## Installing py-ubjson

Before you install: High install friction: the package includes optional C extensions that require a compiler and build tools. The extension is not required but provides significant speed improvement. Package is dormant (last release 2020-04-18, last commit 2024-07-18) with no recent maintenance activity.

License in practice: Apache License 2.0 is permissive; you may use, modify, and distribute this package freely in commercial and private projects provided you include a copy of the license and state significant changes.

Quickstart:

pip install py-ubjson

import ubjson

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

Optional C extension requires a C compiler and build tools; set PYJSON_NO_EXTENSION=1 to skip compilation if needed.

Verify before relying:

- Whether the package works reliably with Python versions beyond 3.8 (classifiers list 3.8 as the latest, but current Python is much newer)
- Current compatibility with modern C extension build systems and Python packaging standards
- Whether the dormant status indicates unmaintained code or stable-enough-to-not-need-updates

## Package facts

- License: Apache License 2.0 (permissive)
- Python support: unspecified
- Install friction: high
- Maintenance: dormant
- Downloads: 1.5M/month (top 5,000 on PyPI)
- Known vulnerabilities: none known

## Tags

binary json encoder decoder, ubjson serialization, compact binary format, json alternative format, efficient data serialization, serialization, binary-format

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