diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,11 @@
 # Changelog
 
+## [0.0.1.1] - 2022-04-26
+
+### Added
+
+* Compatibility with `aeson >= 2.0.0.0`
+
 ## [0.0.1.0] - 2021-12-23
 
 ### Changed
diff --git a/autodocodec.cabal b/autodocodec.cabal
--- a/autodocodec.cabal
+++ b/autodocodec.cabal
@@ -1,11 +1,11 @@
 cabal-version: 1.12
 
--- This file has been generated from package.yaml by hpack version 0.34.5.
+-- This file has been generated from package.yaml by hpack version 0.34.7.
 --
 -- see: https://github.com/sol/hpack
 
 name:           autodocodec
-version:        0.0.1.0
+version:        0.0.1.1
 synopsis:       Self-documenting encoder and decoder
 homepage:       https://github.com/NorfairKing/autodocodec#readme
 bug-reports:    https://github.com/NorfairKing/autodocodec/issues
@@ -27,6 +27,7 @@
   exposed-modules:
       Autodocodec
       Autodocodec.Aeson
+      Autodocodec.Aeson.Compat
       Autodocodec.Aeson.Decode
       Autodocodec.Aeson.Encode
       Autodocodec.Class
diff --git a/src/Autodocodec/Aeson/Compat.hs b/src/Autodocodec/Aeson/Compat.hs
new file mode 100644
--- /dev/null
+++ b/src/Autodocodec/Aeson/Compat.hs
@@ -0,0 +1,60 @@
+{-# LANGUAGE CPP #-}
+
+module Autodocodec.Aeson.Compat where
+
+#if MIN_VERSION_aeson(2,0,0)
+import Data.Aeson.Key (Key)
+import qualified Data.Aeson.Key as K
+import qualified Data.Aeson.KeyMap as KM
+#else
+import qualified Data.HashMap.Strict as HM
+#endif
+import Data.Text (Text)
+
+#if MIN_VERSION_aeson(2,0,0)
+toKey :: Text -> Key
+toKey = K.fromText
+#else
+toKey :: Text -> Text
+toKey = id
+#endif
+
+#if MIN_VERSION_aeson(2,0,0)
+fromKey :: Key -> Text
+fromKey = K.toText
+#else
+fromKey :: Text -> Text
+fromKey = id
+#endif
+
+#if MIN_VERSION_aeson(2,0,0)
+lookupKey :: Key -> KM.KeyMap v -> Maybe v
+lookupKey = KM.lookup
+#else
+lookupKey :: Text -> HM.HashMap Text v -> Maybe v
+lookupKey = HM.lookup
+#endif
+
+#if MIN_VERSION_aeson(2,0,0)
+fromList :: [(Key, v)] -> KM.KeyMap v
+fromList = KM.fromList
+#else
+fromList :: [(Text, v)] -> HM.HashMap Text v
+fromList = HM.fromList
+#endif
+
+#if MIN_VERSION_aeson(2,0,0)
+toList ::  KM.KeyMap v -> [(Key, v)]
+toList = KM.toList
+#else
+toList ::HM.HashMap Text v -> [(Text, v)]
+toList = HM.toList
+#endif
+
+#if MIN_VERSION_aeson(2,0,0)
+map ::  (v1 -> v2) -> KM.KeyMap v1 -> KM.KeyMap v2
+map = KM.map
+#else
+map ::  (v1 -> v2) -> HM.HashMap Text v1 -> HM.HashMap Text v2
+map = HM.map
+#endif
diff --git a/src/Autodocodec/Aeson/Decode.hs b/src/Autodocodec/Aeson/Decode.hs
--- a/src/Autodocodec/Aeson/Decode.hs
+++ b/src/Autodocodec/Aeson/Decode.hs
@@ -6,6 +6,7 @@
 
 module Autodocodec.Aeson.Decode where
 
+import qualified Autodocodec.Aeson.Compat as Compat
 import Autodocodec.Class
 import Autodocodec.Codec
 import Autodocodec.DerivingVia
@@ -13,7 +14,6 @@
 import Data.Aeson as JSON
 import Data.Aeson.Types as JSON
 import Data.HashMap.Strict (HashMap)
-import qualified Data.HashMap.Strict as HM
 import Data.Map (Map)
 import qualified Data.Text as T
 import Data.Vector (Vector)
@@ -111,16 +111,18 @@
       CommentCodec _ c -> go value c
       ReferenceCodec _ c -> go value c
       RequiredKeyCodec k c _ -> do
-        valueAtKey <- (value :: JSON.Object) JSON..: k
-        go valueAtKey c JSON.<?> Key k
+        valueAtKey <- (value :: JSON.Object) JSON..: Compat.toKey k
+        go valueAtKey c JSON.<?> Key (Compat.toKey k)
       OptionalKeyCodec k c _ -> do
-        let mValueAtKey = HM.lookup k (value :: JSON.Object)
-        forM mValueAtKey $ \valueAtKey -> go (valueAtKey :: JSON.Value) c JSON.<?> Key k
+        let key = Compat.toKey k
+            mValueAtKey = Compat.lookupKey key (value :: JSON.Object)
+        forM mValueAtKey $ \valueAtKey -> go (valueAtKey :: JSON.Value) c JSON.<?> Key key
       OptionalKeyWithDefaultCodec k c defaultValue _ -> do
-        let mValueAtKey = HM.lookup k (value :: JSON.Object)
+        let key = Compat.toKey k
+            mValueAtKey = Compat.lookupKey key (value :: JSON.Object)
         case mValueAtKey of
           Nothing -> pure defaultValue
-          Just valueAtKey -> go (valueAtKey :: JSON.Value) c JSON.<?> Key k
+          Just valueAtKey -> go (valueAtKey :: JSON.Value) c JSON.<?> Key key
       OptionalKeyWithOmittedDefaultCodec k c defaultValue mDoc -> go value $ OptionalKeyWithDefaultCodec k c defaultValue mDoc
       PureCodec a -> pure a
       ApCodec ocf oca -> go (value :: JSON.Object) ocf <*> go (value :: JSON.Object) oca
diff --git a/src/Autodocodec/Aeson/Encode.hs b/src/Autodocodec/Aeson/Encode.hs
--- a/src/Autodocodec/Aeson/Encode.hs
+++ b/src/Autodocodec/Aeson/Encode.hs
@@ -5,6 +5,7 @@
 
 module Autodocodec.Aeson.Encode where
 
+import qualified Autodocodec.Aeson.Compat as Compat
 import Autodocodec.Class
 import Autodocodec.Codec
 import Autodocodec.DerivingVia
@@ -49,10 +50,10 @@
 
     goObject :: a -> ObjectCodec a void -> JSON.Object
     goObject a = \case
-      RequiredKeyCodec k c _ -> k JSON..= go a c
+      RequiredKeyCodec k c _ -> Compat.toKey k JSON..= go a c
       OptionalKeyCodec k c _ -> case (a :: Maybe _) of
         Nothing -> mempty
-        Just b -> k JSON..= go b c
+        Just b -> Compat.toKey k JSON..= go b c
       OptionalKeyWithDefaultCodec k c _ mdoc -> goObject (Just a) (OptionalKeyCodec k c mdoc)
       OptionalKeyWithOmittedDefaultCodec k c defaultValue mdoc ->
         if a == defaultValue
@@ -93,10 +94,10 @@
       ReferenceCodec _ c -> go a c
     goObject :: a -> ObjectCodec a void -> JSON.Series
     goObject a = \case
-      RequiredKeyCodec k c _ -> JSON.pair k (go a c)
+      RequiredKeyCodec k c _ -> JSON.pair (Compat.toKey k) (go a c)
       OptionalKeyCodec k c _ -> case (a :: Maybe _) of
         Nothing -> mempty :: JSON.Series
-        Just b -> JSON.pair k (go b c)
+        Just b -> JSON.pair (Compat.toKey k) (go b c)
       OptionalKeyWithDefaultCodec k c _ mdoc -> goObject (Just a) (OptionalKeyCodec k c mdoc)
       OptionalKeyWithOmittedDefaultCodec k c defaultValue mdoc ->
         if a == defaultValue
diff --git a/src/Autodocodec/Class.hs b/src/Autodocodec/Class.hs
--- a/src/Autodocodec/Class.hs
+++ b/src/Autodocodec/Class.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE CPP #-}
 {-# LANGUAGE FlexibleInstances #-}
 {-# LANGUAGE LambdaCase #-}
 {-# LANGUAGE OverloadedLists #-}
@@ -9,6 +10,9 @@
 import Autodocodec.Codec
 import Data.Aeson (FromJSONKey, ToJSONKey)
 import qualified Data.Aeson as JSON
+#if MIN_VERSION_aeson(2,0,0)
+import Data.Aeson.KeyMap (KeyMap)
+#endif
 import Data.HashMap.Strict (HashMap)
 import Data.Hashable (Hashable)
 import Data.Int
@@ -121,6 +125,11 @@
 
 instance (Eq k, Hashable k, FromJSONKey k, ToJSONKey k, HasCodec v) => HasCodec (HashMap k v) where
   codec = HashMapCodec codec
+
+#if MIN_VERSION_aeson(2,0,0)
+instance HasCodec v => HasCodec (KeyMap v) where
+  codec = keyMapCodec codec
+#endif
 
 -- TODO make these instances better once aeson exposes its @Data.Aeson.Parser.Time@ or @Data.Attoparsec.Time@ modules.
 instance HasCodec Day where
diff --git a/src/Autodocodec/Codec.hs b/src/Autodocodec/Codec.hs
--- a/src/Autodocodec/Codec.hs
+++ b/src/Autodocodec/Codec.hs
@@ -1,4 +1,5 @@
 {-# LANGUAGE AllowAmbiguousTypes #-}
+{-# LANGUAGE CPP #-}
 {-# LANGUAGE DeriveGeneric #-}
 {-# LANGUAGE FlexibleInstances #-}
 {-# LANGUAGE GADTs #-}
@@ -15,6 +16,10 @@
 import Control.Monad.State
 import Data.Aeson (FromJSON, FromJSONKey, ToJSON, ToJSONKey)
 import qualified Data.Aeson as JSON
+#if MIN_VERSION_aeson(2,0,0)
+import Data.Aeson.KeyMap (KeyMap)
+import qualified Data.Aeson.KeyMap as KM
+#endif
 import qualified Data.Aeson.Types as JSON
 import Data.HashMap.Strict (HashMap)
 import Data.Hashable
@@ -34,6 +39,7 @@
 
 -- $setup
 -- >>> import Autodocodec.Aeson (toJSONVia, toJSONViaCodec, parseJSONVia, parseJSONViaCodec)
+-- >>> import qualified Autodocodec.Aeson.Compat as Compat
 -- >>> import Autodocodec.Class (HasCodec(codec), requiredField)
 -- >>> import qualified Data.Aeson as JSON
 -- >>> import qualified Data.HashMap.Strict as HM
@@ -66,7 +72,7 @@
   -- | Encode a 'Bool' to a @boolean@ value, and decode a @boolean@ value as a 'Bool'.
   BoolCodec ::
     -- | Name of the @bool@, for error messages and documentation.
-    (Maybe Text) ->
+    Maybe Text ->
     -- |
     JSONCodec Bool
   -- | Encode 'Text' to a @string@ value, and decode a @string@ value as a 'Text'.
@@ -74,7 +80,7 @@
   -- This is named after the primitive type "String" in json, not after the haskell type string.
   StringCodec ::
     -- | Name of the @string@, for error messages and documentation.
-    (Maybe Text) ->
+    Maybe Text ->
     -- |
     JSONCodec Text
   -- | Encode 'Scientific' to a @number@ value, and decode a @number@ value as a 'Scientific'.
@@ -85,7 +91,7 @@
   -- NOTE: We use 'Scientific' here because that is what aeson uses.
   NumberCodec ::
     -- | Name of the @number@, for error messages and documentation.
-    (Maybe Text) ->
+    Maybe Text ->
     -- | Bounds for the number, these are checked and documented
     Maybe NumberBounds ->
     -- |
@@ -111,17 +117,17 @@
   -- | Encode a 'Vector' of values as an @array@ value, and decode an @array@ value as a 'Vector' of values.
   ArrayOfCodec ::
     -- | Name of the @array@, for error messages and documentation.
-    (Maybe Text) ->
+    Maybe Text ->
     -- |
-    (ValueCodec input output) ->
+    ValueCodec input output ->
     -- |
     ValueCodec (Vector input) (Vector output)
   -- | Encode a value as a an @object@ value using the given 'ObjectCodec', and decode an @object@ value as a value using the given 'ObjectCodec'.
   ObjectOfCodec ::
     -- | Name of the @object@, for error messages and documentation.
-    (Maybe Text) ->
+    Maybe Text ->
     -- |
-    (ObjectCodec input output) ->
+    ObjectCodec input output ->
     -- |
     ValueCodec input output
   -- | Match a given value using its 'Eq' instance during decoding, and encode exactly that value during encoding.
@@ -144,7 +150,7 @@
     -- |
     (newInput -> oldInput) ->
     -- |
-    (Codec context oldInput oldOutput) ->
+    Codec context oldInput oldOutput ->
     Codec context newInput newOutput
   -- | Encode/Decode an 'Either' value
   --
@@ -163,9 +169,9 @@
     -- | What type of union we encode and decode
     !Union ->
     -- | Codec for the 'Left' side
-    (Codec context input1 output1) ->
+    Codec context input1 output1 ->
     -- | Codec for the 'Right' side
-    (Codec context input2 output2) ->
+    Codec context input2 output2 ->
     -- |
     Codec context (Either input1 input2) (Either output1 output2)
   -- | A comment codec
@@ -328,6 +334,8 @@
       ValueCodec -> pure $ showString "ValueCodec"
       MapCodec c -> (\s -> showParen (d > 10) $ showString "MapCodec" . s) <$> go 11 c
       HashMapCodec c -> (\s -> showParen (d > 10) $ showString "HashMapCodec" . s) <$> go 11 c
+#if MIN_VERSION_aeson(2,0,0)
+#endif
       EqCodec value c -> (\s -> showParen (d > 10) $ showString "EqCodec " . showsPrec 11 value . showString " " . s) <$> go 11 c
       BimapCodec _ _ c -> (\s -> showParen (d > 10) $ showString "BimapCodec _ _ " . s) <$> go 11 c
       EitherCodec u c1 c2 -> (\s1 s2 -> showParen (d > 10) $ showString "EitherCodec " . showsPrec 11 u . showString " " . s1 . showString " " . s2) <$> go 11 c1 <*> go 11 c2
@@ -540,7 +548,7 @@
 -- Object (fromList [("domain",String "Stars"),("name",String "Varda")])
 -- >>> toJSONViaCodec (Maiar "Sauron")
 -- Object (fromList [("name",String "Sauron")])
--- >>> JSON.parseMaybe parseJSONViaCodec (Object (HM.fromList [("name",String "Olorin")])) :: Maybe Ainur
+-- >>> JSON.parseMaybe parseJSONViaCodec (Object (Compat.fromList [("name",String "Olorin")])) :: Maybe Ainur
 -- Just (Maiar "Olorin")
 --
 -- === WARNING
@@ -931,6 +939,48 @@
   [Text] ->
   ValueCodec input output
 (<??>) c ls = CommentCodec (T.unlines ls) c
+
+-- | Encode a 'HashMap', and decode any 'HashMap'.
+--
+-- Forward-compatible version of 'HashMapCodec'
+--
+-- > hashMapCodec = HashMapCodec
+hashMapCodec ::
+  (Eq k, Hashable k, FromJSONKey k, ToJSONKey k) =>
+  -- |
+  JSONCodec v ->
+  -- |
+  JSONCodec (HashMap k v)
+hashMapCodec = HashMapCodec
+
+-- | Encode a 'Map', and decode any 'Map'.
+--
+-- Forward-compatible version of 'MapCodec'
+--
+-- > mapCodec = MapCodec
+mapCodec ::
+  (Ord k, FromJSONKey k, ToJSONKey k) =>
+  -- |
+  JSONCodec v ->
+  -- |
+  JSONCodec (Map k v)
+mapCodec = MapCodec
+
+#if MIN_VERSION_aeson(2,0,0)
+-- | Encode a 'KeyMap', and decode any 'KeyMap'.
+--
+-- This chooses 'hashMapCodec' or 'mapCodec' based on @ordered-keymap@ flag in aeson.
+keyMapCodec ::
+    -- |
+    JSONCodec v ->
+    -- |
+    JSONCodec (KeyMap v)
+keyMapCodec = case KM.coercionToMap of
+  -- Can coerce to Map, use
+  Just _ -> dimapCodec KM.fromMap KM.toMap . mapCodec
+  -- Cannot coerce to Map, use HashMap instead.
+  Nothing -> dimapCodec KM.fromHashMap KM.toHashMap . hashMapCodec
+#endif
 
 -- | Forward-compatible version of 'ValueCodec'
 --