demjson3
encoder, decoder, and lint/validator for JSON (JavaScript Object Notation) compliant with RFC 7159
Decision gist · record as of 2026-08-14
No. The package is abandoned (last release October 2022, 1392 days ago) with no active maintenance. Python's built-in json module handles standard JSON encoding and decoding adequately for most use cases. Install demjson3 only if you specifically need its advanced error checking, lenient JavaScript parsing, or Decimal precision features and can accept the risk of no future updates or security patches.AI-flagged interpretation of the facts on this page — verify before relying
Before you install
- No runtime dependencies, but package is abandoned with no active maintenance since October 2022.
- High install friction: the package is abandoned (last release 1392 days ago) and requires manual installation via setup.py or direct file copy, with no active maintenance or support.
License · maintenance · safety
GNU LGPL 3.0 (copyleft) — Licensed under GNU LGPL 3.0 (copyleft), which requires derivative works to remain open-source and may impose obligations on proprietary projects that link or bundle this code.
last release 2022-10-22 (1392 days)
0 known vulnerabilities (OSV.dev, 2026-08-14) · 594,367 downloads/mo, #5,844 on PyPI
Alternatives
Verify before relying
pip install demjson3
import demjson3
demjson3.encode(['one', 42, True, None])
demjson3.decode('["one",42,true,null]')- Whether the package works reliably on Python versions beyond 3.9 (classifiers list only up to 3.9).
- Current status of the upstream demjson project and whether demjson3 remains compatible with its evolution.
- Whether jsonlint output formatting issues mentioned in version 2.2.4 remain resolved in 3.0.6.
What it is and what it does
demjson3 is a Python 3-only JSON library that provides encoding, decoding, and strict validation of JSON data. It includes a jsonlint command-line tool for checking JSON files against the JSON specification and detecting portability issues like leading zeros in numbers, duplicate object keys, and integers larger than 53 bits. Unlike Python's built-in json module, demjson3 offers more detailed error reporting, can parse lenient JavaScript-like syntax (comments, unquoted keys), automatically uses Python's Decimal class to avoid floating-point precision loss, and handles Unicode encoding more conservatively for better data portability.
The package is a Python 3-only fork of the original demjson project, dropping Python 2 support. It has no external runtime dependencies and can be used either as an importable module or via the bundled jsonlint script. However, the project is abandoned: the last release was in October 2022, and there is no active maintenance or support.
Use it for
- Validate JSON files for strict RFC 7159 compliance and detect common portability issues before deployment.
- Parse JavaScript-like JSON with comments or unquoted keys in non-strict mode for lenient input handling.
- Ensure numeric precision by automatically promoting large integers and floats to Python Decimal to avoid overflow.
- Pretty-print or reformat JSON documents with customizable indentation and whitespace handling.
- Integrate strict JSON linting into build pipelines or data processing workflows via the jsonlint command.
Worth the install?
AI-flagged interpretation of the facts on this page. Verify before relying on it.
No.
The package is abandoned (last release October 2022, 1392 days ago) with no active maintenance. Python's built-in json module handles standard JSON encoding and decoding adequately for most use cases. Install demjson3 only if you specifically need its advanced error checking, lenient JavaScript parsing, or Decimal precision features and can accept the risk of no future updates or security patches.
Install
demjson3 on PyPI
Before you install
High install friction: the package is abandoned (last release 1392 days ago) and requires manual installation via setup.py or direct file copy, with no active maintenance or support.
No runtime dependencies, but package is abandoned with no active maintenance since October 2022.
License in practice
Licensed under GNU LGPL 3.0 (copyleft), which requires derivative works to remain open-source and may impose obligations on proprietary projects that link or bundle this code.
Quickstart
pip install demjson3
import demjson3
demjson3.encode(['one', 42, True, None])
demjson3.decode('["one",42,true,null]')Verify before relying
- Whether the package works reliably on Python versions beyond 3.9 (classifiers list only up to 3.9).
- Current status of the upstream demjson project and whether demjson3 remains compatible with its evolution.
- Whether jsonlint output formatting issues mentioned in version 2.2.4 remain resolved in 3.0.6.
Package facts
| License | GNU LGPL 3.0 copyleft |
| Python support | Not specified |
| Install friction | High. Source build required |
| Runtime dependencies | None |
| Maintenance | Abandoned 1,392 days since the last release |
| First released | |
| Downloads | 594,367 / month, #5,844 on PyPI 30-day window, as of 2026-08-14 |
| Known vulnerabilities | None known OSV.dev, checked 2026-08-14 |
| Classifiers | Development Status :: 4 - BetaIntended Audience :: DevelopersLicense :: OSI Approved :: GNU Library or Lesser General Public License (LGPL)Operating System :: OS IndependentProgramming Language :: Python :: 3.5Programming Language :: Python :: 3.6Programming Language :: Python :: 3.7Programming Language :: Python :: 3.8Programming Language :: Python :: 3.9Topic :: Internet :: WWW/HTTP :: Dynamic ContentTopic :: Software Development :: Libraries :: Python Modules |
Evidence: demjson3-3.0.6.tar.gz
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