# haskell/aeson

A fast Haskell JSON library

Repository: https://github.com/haskell/aeson
Canonical: https://ross.abutalabs.com/products/aeson
Language: Haskell
License: NOASSERTION
License Family: other
Last push: 2026-08-25T17:38:48+00:00

## Health v2 (maintenance only)
Score: 77/100 (v2, computed 2026-09-03T02:20:16.233290+00:00)
- activity 99, release rhythm 35, longevity 100
- inputs: {"age_days": 5703, "days_push": 8, "days_rel": null, "gap_med": null, "n_releases_24m": 0}
- flags: no_releases, no_license
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 1308, forks 334 (observed 2026-08-28T04:04:19.272585+00:00)

## What it is
aeson is a fast, widely used Haskell library for parsing, encoding, and manipulating JSON data. It provides typeclass-based conversion between Haskell data types and JSON values.

## Use cases
- parse JSON in Haskell
- encode Haskell data types to JSON
- decode JSON responses from an API
- manipulate JSON documents programmatically
- build JSON-based REST APIs in Haskell

## When to choose
- you are writing Haskell and need JSON serialization or parsing
- you need a mature, performant JSON library with a rich ecosystem of integrations

## When to avoid
- you are not working in Haskell
- you need streaming JSON parsing for extremely large documents with minimal memory use (consider specialized streaming libraries)

## Facets
- artifact type: library
- maturity: stable
- function: serialization, parser
- domain: parsers, developer-tools, web-development
- platform: jvm-scripting
- tags: haskell, -parsing, encoding, decoding

## Member repositories
- haskell/aeson (main) score 77

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:04:19.272585+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 2026-08-30T04:50:05.233595+00:00, confidence not recorded.
  - readme: https://github.com/haskell/aeson (fetched 2026-08-28T04:04:19.272585+00:00, sha cb1db1717b10)
- Data as of 2026-08-30T08:39:29.467469+00:00.