The aeson package

[ Tags: bsd3, json, library, text, web ] [ Propose Tags ]

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

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, hashable (>= && <1.2), mtl, old-locale, syb, template-haskell (>=2.5 && <2.10), text (>=, time (<1.5), unordered-containers (>=, vector (>=0.7) [details]
License BSD3
Copyright Copyright 2011 MailRank, Inc.
Author Bryan O'Sullivan <>
Maintainer Bryan O'Sullivan <>
Category Text, Web, JSON
Home page
Bug tracker
Source repo head: git clone
head: hg clone
Uploaded Wed Nov 30 19:14:07 UTC 2011 by BryanOSullivan
Updated Wed May 27 11:20:53 UTC 2015 by AdamBergmark to revision 2   [What is this?]
Distributions Arch:, Debian:, Fedora:, FreeBSD:, LTSHaskell:, NixOS:, Stackage:, openSUSE:
Downloads 381613 total (1309 in the last 30 days)
Rating 2.75 (votes: 21) [estimated by rule of succession]
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Status Docs uploaded by user
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Maintainer's Corner

For package maintainers and hackage trustees

Readme for aeson-

[back to package description]

Welcome to aeson

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

Important note for users of GHCi and Template Haskell

This package depends on the blaze-textual package , and is unfortunately subject to crashes if you use GHCi or Template Haskell in your work.

For complete details, including a workaround, see the writeup in the blaze-textual README.

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,