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.

For release notes, see

Note: if you use GHCi or Template Haskell, please see the README file for important details about building this package, and other packages that depend on it:

Parsing performance on a late 2010 MacBook Pro (2.66GHz Core i7), for mostly-English tweets from Twitter's JSON search API:

Handling heavily-escaped text is a little more work. Here is parsing performance with Japanese tweets, where much of the text is entirely Unicode-escaped.

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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Versions,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, (info)
Dependencies attoparsec (>=, base (==4.*), blaze-builder (>=, blaze-textual (>=, bytestring, containers, deepseq, dlist (>=0.2), ghc-prim (>=0.2), hashable (>= && <1.2), mtl, old-locale, syb, template-haskell (>=2.4 && <2.10), text (>=, time (<1.5), unordered-containers (>=, vector (>=0.7.1) [details]
License BSD3
Copyright (c) 2011 Bryan O'Sullivan (c) 2011 MailRank, Inc.
Author Bryan O'Sullivan <>
Maintainer Bryan O'Sullivan <>
Stability experimental
Category Text, Web, JSON
Home page
Bug tracker
Source repository head: git clone git://
head: hg clone
Uploaded Fri Dec 23 08:18:26 UTC 2011 by BryanOSullivan
Updated Wed May 27 11:22:29 UTC 2015 by AdamBergmark to revision 2
Distributions Arch:, Debian:, Fedora:, FreeBSD:, LTSHaskell:, NixOS:, Stackage:, Tumbleweed:
Downloads 230929 total (266 in the last 30 days)
11 []
Status Docs uploaded by user
Build status unknown [no reports yet]




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Maintainer's Corner

For package maintainers and hackage trustees

Readme for aeson

Readme for aeson-

Welcome to aeson

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,