Fast base64 encoding and decoding for ByteStrings

Version on this page:
LTS Haskell 13.25:
Stackage Nightly 2019-06-12:
Latest on Hackage:

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BSD-3-Clause licensed by Bryan O'Sullivan
Maintained by Herbert Valerio Riedel, Mikhail Glushenkov

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Fast base64 support Hackage version Stackage version Build Status

This package provides a Haskell library for working with base64-encoded data quickly and efficiently, using the ByteString type.


This library is written in pure Haskell, and it’s fast:

  • 250 MB/sec encoding

  • 200 MB/sec strict decoding (per RFC 4648)

  • 100 MB/sec lenient decoding

Get involved!

Please report bugs via the GitHub issue tracker.

Master Git repository:

  • git clone git://


This library is written by Bryan O’Sullivan. It is maintained by Herbert Valerio Riedel and Mikhail Glushenkov.


  • Fixed a write past allocated memory in joinWith (potential security issue). -

  • Changelog not recorded for these versions.

  • Fixed: wrong encoding table on big-endian systems.
  • Fixed: too big indices in encoding table construction.

  • Changelog not recorded up to this version.
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