The aeson package

[Tags:bsd3, library, test]

A JSON parsing and encoding library optimized for ease of use and high performance.

To get started, see the documentation for the Data.Aeson module below.

Parsing performance on a late 2013 MacBook Pro (2.6GHz Core i7), running 64-bit GHC 7.10.1, for mostly-English tweets from Twitter's JSON search API:

Encoding performance on the same machine and data:

(A note on naming: in Greek mythology, Aeson was the father of Jason.)

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Change log
Dependencies attoparsec (>=, base (>=4.5 && <5), base-compat (>=0.9.1 && <0.10), bytestring (>=0.9), bytestring-builder (>=0.10.4 && <1), containers (>=, deepseq (>=1.3), dlist (>=0.2), fail (==4.9.*), ghc-prim (>=0.2), hashable (>=, nats (>=1 && <1.2), scientific (>= && <0.4), semigroups (>=0.18.2 && <0.19), tagged (>=0.8.3 && <0.9), template-haskell (>=2.7), text (>=, time (>=, time-locale-compat (>=0.1.1 && <0.2), transformers (>=, transformers-compat (>=0.3), unordered-containers (>=, vector (>=0.8) [details]
License BSD3
Copyright (c) 2011-2016 Bryan O'Sullivan (c) 2011 MailRank, Inc.
Author Bryan O'Sullivan <>
Maintainer Adam Bergmark <>
Stability experimental
Category Text, Web, JSON
Home page
Bug tracker
Source repository head: git clone git://
head: hg clone
Uploaded Sat Oct 22 13:55:44 UTC 2016 by AdamBergmark
Distributions Arch:, Debian:, Fedora:, FreeBSD:, LTSHaskell:, NixOS:, Stackage:, Tumbleweed:
Downloads 230995 total (318 in the last 30 days)
11 []
Status Docs available [build log]
Last success reported on 2016-10-22 [all 1 reports]




developeroperate in developer modeDisabledManual
fastcompile without optimizationsDisabledManual
bytestring-builderDepend on the bytestring-builder package for backwards compatibility.DisabledAutomatic

Use -f <flag> to enable a flag, or -f -<flag> to disable that flag. More info


Maintainer's Corner

For package maintainers and hackage trustees

Readme for aeson

Readme for aeson-

Welcome to aeson Hackage Build Status

aeson is a fast Haskell library for working with JSON data.

Join in!

We are happy to receive bug reports, fixes, documentation enhancements, and other improvements.

Please report bugs via the github issue tracker.

Master git repository:

  • git clone git://

There's also a Mercurial mirror:

  • hg clone

(You can create and contribute changes using either git or Mercurial.)


This library is written and maintained by Bryan O'Sullivan,