Simpler API

The API below is rather low-level. The Network.HTTP.Simple module provides a higher-level API with built-in support for things like JSON request and response bodies. For most users, this will be an easier place to start. You can read the tutorial at:

https://haskell-lang.org/library/http-client

Lower-level API

This module contains everything you need to initiate HTTP connections. If you want a simple interface based on URLs, you can use simpleHttp. If you want raw power, http is the underlying workhorse of this package. Some examples:

-- Just download an HTML document and print it.
import Network.HTTP.Conduit
import qualified Data.ByteString.Lazy as L

main = simpleHttp "http://www.haskell.org/" >>= L.putStr

This example uses interleaved IO to write the response body to a file in constant memory space.

import Data.Conduit.Binary (sinkFile) -- Exported from the package conduit-extra
import Network.HTTP.Conduit
import Conduit (runConduit, (.|))
import Control.Monad.Trans.Resource (runResourceT)

main :: IO ()
main = do
     request <- parseRequest "http://google.com/"
     manager <- newManager tlsManagerSettings
     runResourceT $ do
         response <- http request manager
         runConduit $ responseBody response .| sinkFile "google.html"

The following headers are automatically set by this module, and should not be added to requestHeaders:

• Cookie
• Content-Length
• Transfer-Encoding

Note: In previous versions, the Host header would be set by this module in all cases. Starting from 1.6.1, if a Host header is present in requestHeaders, it will be used in place of the header this module would have generated. This can be useful for calling a server which utilizes virtual hosting.

Use cookieJar If you want to supply cookies with your request:

{-# LANGUAGE OverloadedStrings #-}
import Network.HTTP.Conduit
import Network
import Data.Time.Clock
import Data.Time.Calendar
import qualified Control.Exception as E
import Network.HTTP.Types.Status (statusCode)

past :: UTCTime
past = UTCTime (ModifiedJulianDay 56200) (secondsToDiffTime 0)

future :: UTCTime
future = UTCTime (ModifiedJulianDay 562000) (secondsToDiffTime 0)

cookie :: Cookie
cookie = Cookie { cookie_name = "password_hash"
                , cookie_value = "abf472c35f8297fbcabf2911230001234fd2"
                , cookie_expiry_time = future
                , cookie_domain = "example.com"
                , cookie_path = "/"
                , cookie_creation_time = past
                , cookie_last_access_time = past
                , cookie_persistent = False
                , cookie_host_only = False
                , cookie_secure_only = False
                , cookie_http_only = False
                }

main = do
     request' <- parseRequest "http://example.com/secret-page"
     manager <- newManager tlsManagerSettings
     let request = request' { cookieJar = Just $ createCookieJar [cookie] }
     fmap Just (httpLbs request manager) `E.catch`
             (\ex -> case ex of
                 HttpExceptionRequest _ (StatusCodeException res _) ->
                     if statusCode (responseStatus res) == 403
                       then (putStrLn "login failed" >> return Nothing)
                       else return Nothing
                 _ -> E.throw ex)

Cookies are implemented according to RFC 6265.

Note that by default, the functions in this package will throw exceptions for non-2xx status codes. If you would like to avoid this, you should use checkStatus, e.g.:

import Data.Conduit.Binary (sinkFile)
import Network.HTTP.Conduit
import qualified Data.Conduit as C
import Network

main :: IO ()
main = do
     request' <- parseRequest "http://www.yesodweb.com/does-not-exist"
     let request = request' { checkStatus = \_ _ _ -> Nothing }
     manager <- newManager tlsManagerSettings
     res <- httpLbs request manager
     print res

By default, when connecting to websites using HTTPS, functions in this package will throw an exception if the TLS certificate doesn't validate. To continue the HTTPS transaction even if the TLS cerficate validation fails, you should use mkManagerSetttings as follows:

import Network.Connection (TLSSettings (..))
import Network.HTTP.Conduit

main :: IO ()
main = do
    request <- parseRequest "https://github.com/"
    let settings = mkManagerSettings (TLSSettingsSimple True False False) Nothing
    manager <- newManager settings
    res <- httpLbs request manager
    print res

For more information, please be sure to read the documentation in the Network.HTTP.Client module.

Network.HTTP.Client.MultipartFormData provides an API for building form-data request bodies.