diff --git a/Keys/Random.hs b/Keys/Random.hs
--- a/Keys/Random.hs
+++ b/Keys/Random.hs
@@ -19,7 +19,7 @@
 
 ------------------------------------------------------------------------------
 charRangeEnd :: Word8
-charRangeEnd = c2w8 'z'
+charRangeEnd = c2w8 'Z'
 
 ------------------------------------------------------------------------------
 genString :: Gen (PrimState IO) -> IO B.ByteString
diff --git a/Keys/UUID.hs b/Keys/UUID.hs
--- a/Keys/UUID.hs
+++ b/Keys/UUID.hs
@@ -2,8 +2,10 @@
 module Keys.UUID where
 
 import Prelude
+import Data.Bits
+import Data.Char
 import Data.UUID (fromString, toString, toWords, fromWords)
-import qualified Data.UUID as U (UUID, nil)
+import qualified Data.UUID as U (UUID(..), nil)
 import Data.UUID.V4(nextRandom)
 import Control.Applicative ((<$>))
 -- import Data.Aeson.Types (FromJSON(..), ToJSON(..), typeMismatch)
@@ -12,13 +14,18 @@
 -- import Control.Monad(mzero)
 import Data.Data
 import Data.Hashable
-import Data.Text (unpack, pack)
+import Control.Monad
+import Data.Text (unpack, pack, Text)
+import qualified Data.Text as T
 import Keys.Random
 import Data.SafeCopy
 import Data.Serialize
 import Web.PathPieces
 import Foreign.Storable
 import Text.Blaze
+import Data.Word
+import Data.Aeson
+import qualified Data.Aeson as Aeson
 
 newtype UUID = UUID U.UUID
     deriving(Ord, Eq, Data, Typeable, Storable)
@@ -34,6 +41,23 @@
 strUUID :: UUID -> String
 strUUID (UUID u) = toString u
 
+txtUUID :: UUID -> Text
+txtUUID (UUID u) = uuidToText (toWords u) 
+    where
+        uuidToText :: (Word32, Word32, Word32, Word32) -> Text
+        uuidToText (w0, w1, w2, w3) = hexw w0 $ hexw' w1 $ hexw' w2 $ hexw w3 T.empty
+        hexw :: Word32 -> Text -> Text
+        hexw  w s = hexn w 28 `T.cons` hexn w 24 `T.cons` hexn w 20 `T.cons` hexn w 16
+                  `T.cons` hexn w 12 `T.cons` hexn w  8 `T.cons` hexn w  4 `T.cons` hexn w  0 `T.cons` s
+
+        hexw' :: Word32 -> Text -> Text 
+        hexw' w s = '-' `T.cons` hexn w 28 `T.cons` hexn w 24 `T.cons` hexn w 20 `T.cons` hexn w 16
+                    `T.cons` '-' `T.cons` hexn w 12 `T.cons` hexn w  8 `T.cons` hexn w  4 `T.cons` hexn w  0 `T.cons` s
+
+        hexn :: Word32 -> Int -> Char
+        hexn w r = intToDigit $ fromIntegral ((w `shiftR` r) .&. 0xf)
+        
+
 nil :: UUID
 nil = UUID U.nil
 
@@ -46,6 +70,14 @@
 
 instance ToMarkup UUID where
     toMarkup u = toMarkup $ pack $ strUUID u
+
+instance ToJSON UUID where
+    toJSON u = Aeson.String (txtUUID u)
+instance FromJSON UUID where
+    parseJSON (Aeson.String s) = case fromString (T.unpack s) of
+                                    Just u -> return $ UUID u
+                                    Nothing -> mzero
+    parseJSON _ = mzero
 
 {- these can be useful in postgresql-simple:
 instance FromField UUID where
diff --git a/special-keys.cabal b/special-keys.cabal
--- a/special-keys.cabal
+++ b/special-keys.cabal
@@ -1,5 +1,5 @@
 name:                special-keys
-version:             0.1.0.2
+version:             0.1.0.3
 synopsis:            Simple data types that help me here and there. 
 description:         Datatypes that I use as keys to index other data types. Here you will find a wrap of UUID and also constraints on Text so that it never exceeds a given number of characters.
 license:             BSD3