# ijl/orjson

Fast, correct Python JSON library supporting dataclasses, datetimes, and numpy

Repository: https://github.com/ijl/orjson
Canonical: https://ross.abutalabs.com/products/orjson
Language: Python
License: Apache-2.0
License Family: permissive
Topics: json, python, rust, serialization, datetime, pyo3, dataclasses, deserialization, numpy
Last push: 2026-08-20T13:42:01+00:00

## Health v2 (maintenance only)
Score: 98/100 (v2, computed 2026-09-03T02:20:16.233290+00:00)
- activity 98, release rhythm 98, longevity 100
- inputs: {"age_days": 2842, "days_push": 13, "days_rel": 19, "gap_med": 21, "n_releases_24m": 22}
- flags: none
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 8214, forks 327 (observed 2026-08-28T04:10:19.604454+00:00)

## What it is
orjson is a fast, correct JSON serialization/deserialization library for Python, implemented in Rust via PyO3. It natively serializes dataclasses, datetimes, numpy arrays, and UUIDs, and benchmarks significantly faster than the standard json library.

## Use cases
- serialize json faster than the standard library
- serialize dataclasses and datetimes to json
- serialize numpy arrays to json
- parse json strictly per RFC 8259
- speed up json encoding in a python api
- dump json with uuid support

## When to choose
- you need maximum JSON serialization/deserialization performance in CPython
- you need native serialization of dataclasses, datetimes, numpy arrays, or UUIDs
- you need strict RFC 8259 and UTF-8 compliance

## When to avoid
- you need file or line-delimited JSON I/O helpers
- you use PyPy, embedded Python on Android/iOS, or subinterpreters
- you need a pure-Python dependency

## Facets
- artifact type: library
- maturity: stable
- function: serialization, parser
- domain: developer-tools, apis
- platform: python, windows
- tags: json, rust, pyo3, performance, dataclasses, numpy, datetime, data-engineering, linux, macos

## Member repositories
- ijl/orjson (main) score 98

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:10:19.604454+00:00.
- Health v2: computed from the inputs above; adoption is never an input.
- Inferred fields (summary, facets, guidance): AI-extracted, prompt v1, taxonomy v1, on 2026-08-29T17:29:32.082110+00:00, confidence not recorded.
  - readme: https://github.com/ijl/orjson (fetched 2026-08-28T04:10:19.604454+00:00, sha c31a428b744d)
- Data as of 2026-08-30T08:39:29.467469+00:00.