aeson: Fast JSON parsing and generation

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

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

Parsing performance with GHC 6.12.3 on a late 2010 MacBook Pro (2.66GHz Core i7), for mostly-English tweets from Twitter's JSON search API:

  • 854 bytes: 21054 msg/sec (17.1 MB/sec)

  • 6.4 KB: 4545 msg/sec (28.6 MB/sec)

  • 31.2 KB: 856 msg/sec (26.1 MB/sec)

  • 61.5 KB: 403 msg/sec (24.2 MB/sec)

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:

  • 14.6 KB: 1250 msg/sec (17.9 MB/sec)

  • 44.1 KB: 363 msg/sec (15.6 MB/sec)

Encoding performance on the same machine and data:

  • 854 bytes: 10647 msg/sec (8.7 MB/sec)

  • 6.4 KB: 2098 msg/sec (13.2 MB/sec)

  • 31.2 KB: 422 msg/sec (12.9 MB/sec)

  • 61.5 KB: 219 msg/sec (13.2 MB/sec)

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

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Versions [RSS],,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, (info)
Dependencies attoparsec (>=, base (<4.4), blaze-builder (>=, bytestring, containers (>=0.4.2), deepseq, old-locale, text (>=, time (<1.5), vector (>=0.7) [details]
License BSD-3-Clause
Copyright Copyright 2011 MailRank, Inc.
Author Bryan O'Sullivan <>
Maintainer Bryan O'Sullivan <>
Revised Revision 1 made by HerbertValerioRiedel at 2014-12-31T17:32:22Z
Category Text, Web, JSON
Home page
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Source repo head: git clone
head: hg clone
Uploaded by BryanOSullivan at 2011-01-27T23:36:19Z
Distributions Arch:, Debian:, Fedora:, FreeBSD:, LTSHaskell:, NixOS:, Stackage:, openSUSE:
Reverse Dependencies 2272 direct, 5467 indirect [details]
Downloads 586241 total (1081 in the last 30 days)
Rating 3.0 (votes: 40) [estimated by Bayesian average]
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Status Docs uploaded by user
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Readme for aeson-

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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,