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The web development community in Haskell has recently had a large boost in activity, resulting in a plethora of choices in libraries. As usual, a breadth of options is a double edged sort: you can choose the tools more to your style, but it is harder to find quality tools.

This document is meant to be an up-to-date listing of different libraries available to perform various tasks related to web development. We want to strike a balance here between enough information to make an informed decision, while keeping a good signal-to-noise ratio. As such, for editors, please try to include the following information on each library:

  • Name
  • Most recent version, and release date
  • Link to the code (either Hackage, or elsewhere if not on Hackage)
  • A short summary of what the library does. In particular, what makes this library different than others
  • Links to more documentation. If there are lots of links, consider creating a separate Wiki page for those links, so as not to clutter this page.
  • Links to sample code. Both short snippets and full-scale applications are welcome. Again, create a separate Wiki page as necessary.
  • Dependencies on other packages. For example, a web framework should list its choice of templating system, server, etc.



Interfaces provide an abstraction between servers and applications, allowing different servers to be swapped easily.


Current version: Hack 2009.10.30. Released: October 30, 2009.

Hack is a simple interface for applications. Based on Ruby's Rack, it presents a very low barrier to entry. Unlike WAI, it uses lazy bytestrings for request and response bodies, making it easier to use for some. Many backends are available, for numerous backends; simply search hackage for "hack-handler-".

Samples: None.

Dependencies: None.

WAI (Web Application Interface)

Current version: WAI 0.1.0. Released: May 21, 2010.

The WAI is designed to be a type-safe and performant interface. Type safety is achieved by having data types such as RequestHeader, ResponseHeader, HttpVersion, as opposed to simply using Strings or ByteStrings. Performance is achieved by using an enumerator interface, allowing constant-space response construction without needing lazy I/O. Backends available are currently a simple server, CGI and FastCGI. There is also a Snap Framework backend in the works, waiting on some API changes in Snap.

Samples: Basic sample application

Dependencies: None


Old Content

Wiki pages

External links