# ultrajson/ultrajson

Ultra fast JSON decoder and encoder written in C with Python bindings

Repository: https://github.com/ultrajson/ultrajson
Canonical: https://ross.abutalabs.com/products/ultrajson
Homepage: https://pypi.org/project/ujson/
Language: C++
License: NOASSERTION
License Family: other
Topics: python, c, ultrajson, json, decoder, encoder, ujson
Last push: 2026-08-13T23:08:23+00:00

## Health v2 (maintenance only)
Score: 90/100 (v2, computed 2026-09-03T02:20:16.233290+00:00)
- activity 97, release rhythm 76, longevity 100
- inputs: {"age_days": 5666, "days_push": 20, "days_rel": 80, "gap_med": 54, "n_releases_24m": 4}
- flags: no_license
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 4497, forks 385 (observed 2026-08-28T04:08:51.427183+00:00)

## What it is
UltraJSON (ujson) is an ultra-fast JSON encoder and decoder written in pure C with Python bindings, usable as a drop-in replacement for the standard json module. It is now in maintenance-only mode, with users encouraged to migrate to orjson.

## Use cases
- speed up json serialization in python
- fast json parsing for large payloads
- drop-in replacement for python json module
- encode json with html-safe escaping
- decode json faster than stdlib

## When to choose
- you need faster JSON encoding/decoding than the Python standard library and cannot use orjson
- you have an existing codebase already depending on ujson

## When to avoid
- starting a new project - the maintainers recommend orjson instead
- you need new features or non-critical bug fixes, since only critical/security issues are accepted

## Facets
- artifact type: library
- maturity: maintenance
- function: serialization, parser
- domain: developer-tools, backend
- platform: python, cross-platform
- tags: json, c-extension, ujson, encoder, decoder, performance, data-engineering

## Member repositories
- ultrajson/ultrajson (main) score 90

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:08:51.427183+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 2026-08-29T18:20:27.102100+00:00, confidence not recorded.
  - readme: https://github.com/ultrajson/ultrajson (fetched 2026-08-28T04:08:51.427183+00:00, sha 32db61660b07)
  - homepage: https://pypi.org/project/ujson/ (fetched 2026-08-29T09:06:34.191367+00:00, sha 4b4e8fead74a)
- Data as of 2026-08-30T08:39:29.467469+00:00.