diff --git a/Yesod/Json.hs b/Yesod/Json.hs
--- a/Yesod/Json.hs
+++ b/Yesod/Json.hs
@@ -1,144 +1,1 @@
-{-# LANGUAGE TypeSynonymInstances, OverloadedStrings #-}
-{-# LANGUAGE CPP #-}
-{-# OPTIONS_GHC -fno-warn-orphans #-}
-module Yesod.Json
-    ( -- * Convert from a JSON value
-      defaultLayoutJson
-    , jsonToRepJson
-
-      -- * Convert to a JSON value
-    , parseJsonBody
-    , parseJsonBody_
-
-      -- * Produce JSON values
-    , J.Value (..)
-    , object
-    , array
-    , (.=)
-
-      -- * Convenience functions
-    , jsonOrRedirect
-    , acceptsJson
-    ) where
-
-import Yesod.Handler (GHandler, waiRequest, lift, invalidArgs, redirect)
-import Yesod.Content
-    ( ToContent (toContent), RepHtmlJson (RepHtmlJson), RepHtml (RepHtml)
-    , RepJson (RepJson), Content (ContentBuilder)
-    )
-import Yesod.Core (defaultLayout, Yesod)
-import Yesod.Widget (GWidget)
-import Yesod.Routes.Class
-import Control.Arrow (second)
-import Control.Applicative ((<$>))
-import Control.Monad (join)
-import qualified Data.Aeson as J
-import qualified Data.Aeson.Parser as JP
-import Data.Aeson ((.=))
-import qualified Data.Aeson.Encode as JE
-import Data.Aeson.Encode (fromValue)
-import Data.Conduit.Attoparsec (sinkParser)
-import Data.Text (Text, pack)
-import qualified Data.Vector as V
-import Text.Julius (ToJavascript (..))
-import Data.Text.Lazy.Builder (fromLazyText)
-import Data.Text.Lazy.Encoding (decodeUtf8)
-import Data.Text.Lazy.Builder (toLazyText)
-import qualified Blaze.ByteString.Builder.Char.Utf8 as Blaze
-import Data.Conduit
-import Network.Wai (requestBody, requestHeaders)
-import Network.Wai.Parse (parseHttpAccept)
-import qualified Data.ByteString.Char8 as B8
-import Safe (headMay)
-
-#if !MIN_VERSION_yesod_core(1, 1, 5)
-instance ToContent J.Value where
-    toContent = flip ContentBuilder Nothing
-              . Blaze.fromLazyText
-              . toLazyText
-              . fromValue
-#endif
-
--- | Provide both an HTML and JSON representation for a piece of
--- data, using the default layout for the HTML output
--- ('defaultLayout').
---
--- /Since: 0.3.0/
-defaultLayoutJson :: (Yesod master, J.ToJSON a)
-                  => GWidget sub master ()  -- ^ HTML
-                  -> a                      -- ^ JSON
-                  -> GHandler sub master RepHtmlJson
-defaultLayoutJson w json = do
-    RepHtml html' <- defaultLayout w
-    return $ RepHtmlJson html' $ toContent (J.toJSON json)
-
--- | Wraps a data type in a 'RepJson'.  The data type must
--- support conversion to JSON via 'J.ToJSON'.
---
--- /Since: 0.3.0/
-jsonToRepJson :: J.ToJSON a => a -> GHandler sub master RepJson
-jsonToRepJson = return . RepJson . toContent . J.toJSON
-
--- | Parse the request body to a data type as a JSON value.  The
--- data type must support conversion from JSON via 'J.FromJSON'.
--- If you want the raw JSON value, just ask for a @'J.Result'
--- 'J.Value'@.
---
--- /Since: 0.3.0/
-parseJsonBody :: J.FromJSON a => GHandler sub master (J.Result a)
-parseJsonBody = do
-    req <- waiRequest
-    eValue <- lift
-            $ runExceptionT
-            $ transPipe lift (requestBody req)
-           $$ sinkParser JP.value'
-    return $ case eValue of
-        Left e -> J.Error $ show e
-        Right value -> J.fromJSON value
-
--- | Same as 'parseJsonBody', but return an invalid args response on a parse
--- error.
-parseJsonBody_ :: J.FromJSON a => GHandler sub master a
-parseJsonBody_ = do
-    ra <- parseJsonBody
-    case ra of
-        J.Error s -> invalidArgs [pack s]
-        J.Success a -> return a
-
-#if !MIN_VERSION_shakespeare_js(1, 0, 2)
-instance ToJavascript J.Value where
-    toJavascript = fromLazyText . decodeUtf8 . JE.encode
-#endif
-
--- | Convert a list of pairs to an 'J.Object'.
-object :: J.ToJSON a => [(Text, a)] -> J.Value
-object = J.object . map (second J.toJSON)
-
--- | Convert a list of values to an 'J.Array'.
-array :: J.ToJSON a => [a] -> J.Value
-array = J.Array . V.fromList . map J.toJSON
-
--- | jsonOrRedirect simplifies the scenario where a POST handler sends a different
--- response based on Accept headers:
---
---     1. 200 with JSON data if the client prefers
---     @application\/json@ (e.g. AJAX, see 'acceptsJSON').
---
---     2. 3xx otherwise, following the PRG pattern.
-jsonOrRedirect :: (Yesod master, J.ToJSON a)
-               => Route master -- ^ Redirect target
-               -> a            -- ^ Data to send via JSON
-               -> GHandler sub master RepJson
-jsonOrRedirect r j = do
-    q <- acceptsJson
-    if q then jsonToRepJson (J.toJSON j)
-         else redirect r
-
--- | Returns @True@ if the client prefers @application\/json@ as
--- indicated by the @Accept@ HTTP header.
-acceptsJson :: Yesod master => GHandler sub master Bool
-acceptsJson =  maybe False ((== "application/json") . B8.takeWhile (/= ';'))
-            .  join
-            .  fmap (headMay . parseHttpAccept)
-            .  lookup "Accept" . requestHeaders
-           <$> waiRequest
+module Yesod.Json () where
diff --git a/test/Spec.hs b/test/Spec.hs
deleted file mode 100644
--- a/test/Spec.hs
+++ /dev/null
@@ -1,47 +0,0 @@
-{-# LANGUAGE OverloadedStrings, TemplateHaskell, QuasiQuotes, TypeFamilies, MultiParamTypeClasses #-}
-import Yesod.Core
-import Yesod.Json
-import Test.Hspec
-import qualified Data.Map as Map
-import Network.Wai.Test
-import Data.Text (Text)
-
-data App = App
-
-mkYesod "App" [parseRoutes|
-/ HomeR GET
-|]
-
-instance Yesod App
-
-getHomeR :: Handler RepPlain
-getHomeR = do
-    val <- parseJsonBody_
-    case Map.lookup ("foo" :: Text) val of
-        Nothing -> invalidArgs ["foo not found"]
-        Just foo -> return $ RepPlain $ toContent (foo :: Text)
-
-main :: IO ()
-main = do
-    app <- toWaiApp App
-    hspec $ describe "Yesod.Json" $ do
-        it "parses valid content" $ flip runSession app $ do
-            sres <- srequest SRequest
-                { simpleRequest = defaultRequest
-                , simpleRequestBody = "{\"foo\":\"bar\"}"
-                }
-            assertStatus 200 sres
-            assertBody "bar" sres
-        it "400 for bad JSON" $ flip runSession app $ do
-            sres <- srequest SRequest
-                { simpleRequest = defaultRequest
-                , simpleRequestBody = "{\"foo\":\"bar\""
-                }
-            assertStatus 400 sres
-        it "400 for bad structure" $ flip runSession app $ do
-            sres <- srequest SRequest
-                { simpleRequest = defaultRequest
-                , simpleRequestBody = "{\"foo2\":\"bar\"}"
-                }
-            assertStatus 400 sres
-            assertBodyContains "foo not found" sres
diff --git a/yesod-json.cabal b/yesod-json.cabal
--- a/yesod-json.cabal
+++ b/yesod-json.cabal
@@ -1,48 +1,22 @@
 name:            yesod-json
-version:         1.1.2.2
+version:         1.2.0
 license:         MIT
 license-file:    LICENSE
 author:          Michael Snoyman <michael@snoyman.com>
 maintainer:      Michael Snoyman <michael@snoyman.com>
-synopsis:        Generate content for Yesod using the aeson package.
+synopsis:        Generate content for Yesod using the aeson package. (deprecated)
 category:        Web, Yesod
 stability:       Stable
 cabal-version:   >= 1.8
 build-type:      Simple
 homepage:        http://www.yesodweb.com/
-description:     Generate content for Yesod using the aeson package.
+description:     Since version 1.2 of Yesod, the functionality provided by this module is provided by yesod-core itself. You no longer need to use this package.
 
 library
     build-depends:   base                  >= 4        && < 5
-                   , yesod-core            >= 1.1
-                   , yesod-routes          >= 1.1
-                   , aeson                 >= 0.5
-                   , text                  >= 0.8
-                   , shakespeare-js        >= 1.0
-                   , vector                >= 0.9
-                   , containers            >= 0.2
-                   , blaze-builder
-                   , attoparsec-conduit    >= 0.5
-                   , conduit               >= 0.5
-                   , transformers          >= 0.2.2
-                   , wai                   >= 1.3
-                   , wai-extra             >= 1.3
-                   , bytestring            >= 0.9
-                   , safe                  >= 0.2
+                   , yesod-core            >= 1.2
     exposed-modules: Yesod.Json
     ghc-options:     -Wall
-
-test-suite tests
-    type: exitcode-stdio-1.0
-    main-is: Spec.hs
-    hs-source-dirs: test
-    build-depends: base
-                 , wai-test
-                 , hspec
-                 , yesod-json
-                 , yesod-core
-                 , text
-                 , containers
 
 source-repository head
   type:     git