Suave is a simple web development F# library providing a lightweight web server and a set of combinators to manipulate route flow and task composition.
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Suave is a simple web development F# library providing a lightweight web server and a set of combinators to manipulate route flow and task composition. Suave is inspired in the simplicity of Happstack and born out of the necessity of embedding web server capabilities in my own applications. Still in its early stages Suave supports Websocket, HTTPS, multiple TCP/IP bindings, Basic Access Authentication, Keep-Alive.

Suave also takes advantage of F# asynchronous workflows to perform non-blocking IO. In fact, Suave is written in a completely non-blocking fashion throughout.

Sponsored by qvitoo – A.I. bookkeeping and Suave in production since many years.

Build Status

Platform Status
Windows Build status
Mono/Linux Build status

What follows is a tutorial on how to create applications. Scroll past the tutorial to see detailed function documentation.

Tutorial: Hello World!

The simplest Suave application is a simple HTTP server that greets all visitors with the string "Hello World!"

open Suave

startWebServer defaultConfig (Successful.OK "Hello World!")

Now that you've discovered how to do "Hello World!", go read the rest of the documentation – editable in the docs folder.


We have a NuGet ready for your testing needs; Suave is an excellent server for running in-process integation tests, as it's very fast to spawn. On an ordinary laptop, running hundreds of randomised tests and micro-benchmarks as well as all Suave unit tests, take about 5 seconds on mono.

Start by installing:

paket add nuget suave.testing

You can now use it:

open Suave
open Suave.Testing
open Expecto

testCase "parsing a large multipart form" <| fun _ ->

  let res =
    runWithConfig (OK "hi")
    |> req HttpMethod.POST "/" (Some byteArrayContent)

  Expect.equal res "hi" "Should get the correct result"

All of our tests use this assembly; you can do too.

How to Build

We're using a cross-platform build suite called albacore/rake.

Or build using:




Build prerequisites

On Linux and OS X/macOS you should have ruby out of the box (you might need to install bundler though). On Windows, you have to install it.

To execute the build script, invoke following commands:

bundle exec rake

After you managed to build with the rake script, you can also use ./ on any OS or build.cmd on Windows which only compile solution and run tests.

Libuv installation

On OS X:

brew install libuv --universal
and then `export LD_LIBRARY_PATH=/usr/local/lib:/usr/lib:/lib`

On Windows:

@powershell -NoProfile -ExecutionPolicy Bypass -Command "Start-FileDownload ''"
7z x & cd libuv-1.7.5 & vcbuild.bat x86 shared debug
mkdir src\\Suave.Tests\\bin\\Release\\ & cp libuv-1.7.5\\Debug\\libuv.dll src\\Suave.Tests\\bin\\Release\\libuv.dll

On Linux Ubuntu/Debian:

sudo apt-get install automake libtool
curl -sSL | sudo tar zxfv - -C /usr/local/src
cd /usr/local/src/libuv-1.7.5
sudo sh
sudo ./configure
sudo make
sudo make install
sudo rm -rf /usr/local/src/libuv-1.7.5 && cd ~/
sudo ldconfig

Coding Guidelines

Suave.X where X is a module is where we expect users to look. We don't expect users of the library to have to look at Y in Suave.X.Y, so for server-specific code, please stick to the Y module/namespace. That way we make the API discoverable.

Style Guide

Two space indentation.

match x with // '|' characters at base of 'match'
| A     -> ()
| Bcdef -> "aligned arrows" // space after '|' character


Let type annotations be specified with spaces after the argument symbol and before the type.

module MyType =
  let ofString (scheme : string) =
    // ...

Method formatting with no spaces after/before normal parenthesis

let myMethodName firstArg (second : WithType) = async { // and monad builder
  return! f firstArg second
  } // at base of 'let' + 2 spaces

You need to document your methods with '///' to create XML-doc. A XML documentation file is generated together with the compilation and is distributed with the NuGet so that others can read your code's intentions easily.

Don't put unnecessary parenthesis unless it makes the code more clear.

When writing functions that take some sort of 'configuration' or that you can imagine would like to be called with a parameter which is almost always the same value for another function body's call-site, put that parameter before more-often-varying parameters in the function signature.


Run Tests as a console app. Return status code = 0 means success.

Upgrade openssl

Windows: paket update openssl.redist

OS X: brew install openssl && brew update openssl && cp /usr/local/Cellar/openssl/1.0.1j_1/lib/ .

Linux: ...


Chat Room

We have a chat room in case you feel like chatting a bit.

Chat Room