diff --git a/src/Data/OpenApi.hs b/src/Data/OpenApi.hs
index a9ce8f3d..9ece120a 100644
--- a/src/Data/OpenApi.hs
+++ b/src/Data/OpenApi.hs
@@ -119,6 +119,7 @@ module Data.OpenApi (
   -- ** Miscellaneous
   MimeList(..),
   URL(..),
+  SpecificationExtensions (..),
 ) where
 
 import Data.OpenApi.Lens
diff --git a/src/Data/OpenApi/Aeson/Compat.hs b/src/Data/OpenApi/Aeson/Compat.hs
index c516a4e1..90413402 100644
--- a/src/Data/OpenApi/Aeson/Compat.hs
+++ b/src/Data/OpenApi/Aeson/Compat.hs
@@ -14,6 +14,9 @@ import qualified Data.HashMap.Strict.InsOrd as InsOrdHashMap
 import qualified Data.Text                  as T
 
 #if MIN_VERSION_aeson(2,0,0)
+filterWithKey :: (T.Text -> v -> Bool) -> KeyMap.KeyMap v -> KeyMap.KeyMap v
+filterWithKey p = KeyMap.filterWithKey (\k v -> p (keyToText k) v)
+
 deleteKey :: Key -> KeyMap.KeyMap v -> KeyMap.KeyMap v
 deleteKey = KeyMap.delete
 
@@ -43,7 +46,13 @@ lookupKey = KeyMap.lookup . Key.fromText
 
 hasKey :: T.Text -> KeyMap.KeyMap a -> Bool
 hasKey = KeyMap.member . Key.fromText
+
+filterKeys :: (Key -> Bool) -> KeyMap.KeyMap a -> KeyMap.KeyMap a
+filterKeys p = KeyMap.filterWithKey (\key _ -> p key)
 #else
+filterWithKey :: (T.Text -> v -> Bool) -> HM.HashMap T.Text v -> HM.HashMap T.Text v
+filterWithKey = HM.filterWithKey
+
 deleteKey :: T.Text -> HM.HashMap T.Text v -> HM.HashMap T.Text v
 deleteKey = HM.delete
 
@@ -73,4 +82,7 @@ lookupKey = HM.lookup
 
 hasKey :: T.Text -> HM.HashMap T.Text a -> Bool
 hasKey = HM.member
+
+filterKeys :: (T.Text -> Bool) -> HM.HashMap T.Text a -> HM.HashMap T.Text a
+filterKeys p = HM.filterWithKey (\key _ -> p key)
 #endif
diff --git a/src/Data/OpenApi/Internal.hs b/src/Data/OpenApi/Internal.hs
index b9be5292..2d8101e8 100644
--- a/src/Data/OpenApi/Internal.hs
+++ b/src/Data/OpenApi/Internal.hs
@@ -14,6 +14,7 @@
 {-# LANGUAGE TemplateHaskell #-}
 {-# LANGUAGE TypeFamilies #-}
 {-# LANGUAGE UndecidableInstances #-}
+{-# LANGUAGE TupleSections #-}
 module Data.OpenApi.Internal where
 
 import Prelude ()
@@ -48,16 +49,17 @@ import           Text.Read             (readMaybe)
 import           Data.HashMap.Strict.InsOrd (InsOrdHashMap)
 import qualified Data.HashMap.Strict.InsOrd as InsOrdHashMap
 
-import Data.OpenApi.Aeson.Compat        (deleteKey)
+import Data.OpenApi.Aeson.Compat        (deleteKey, filterKeys, objectToList, keyToText)
 import Data.OpenApi.Internal.AesonUtils (AesonDefaultValue (..), HasSwaggerAesonOptions (..),
                                          mkSwaggerAesonOptions, saoAdditionalPairs, saoSubObject,
                                          sopSwaggerGenericParseJSON, sopSwaggerGenericToEncoding,
-                                         sopSwaggerGenericToJSON, sopSwaggerGenericToJSONWithOpts)
+                                         sopSwaggerGenericToJSON, sopSwaggerGenericToJSONWithOpts, sopSwaggerGenericParseJSONWithOpts)
 import Data.OpenApi.Internal.Utils
 import Generics.SOP.TH                  (deriveGeneric)
 import Data.Version
 import Control.Monad (unless)
 import Text.ParserCombinators.ReadP (readP_to_S)
+import Data.Maybe (catMaybes)
 
 -- $setup
 -- >>> :seti -XDataKinds
@@ -104,6 +106,8 @@ data OpenApi = OpenApi
 
   , -- | The spec of OpenApi this spec adheres to. Must be between 'lowerOpenApiSpecVersion' and 'upperOpenApiSpecVersion'
     _openApiOpenapi :: OpenApiSpecVersion
+    -- | Specification Extensions
+  , _openApiExtensions :: SpecificationExtensions
   } deriving (Eq, Show, Generic, Data, Typeable)
 
 -- | This is the lower version of the OpenApi Spec this library can parse or produce
@@ -137,6 +141,9 @@ data Info = Info
     -- | The version of the OpenAPI document (which is distinct from the
     -- OpenAPI Specification version or the API implementation version).
   , _infoVersion :: Text
+
+    -- | Specification Extensions
+  , _infoExtensions :: SpecificationExtensions
   } deriving (Eq, Show, Generic, Data, Typeable)
 
 -- | Contact information for the exposed API.
@@ -149,6 +156,9 @@ data Contact = Contact
 
     -- | The email address of the contact person/organization.
   , _contactEmail :: Maybe Text
+
+    -- | Specification Extensions
+  , _contactExtensions :: SpecificationExtensions
   } deriving (Eq, Show, Generic, Data, Typeable)
 
 -- | License information for the exposed API.
@@ -158,10 +168,13 @@ data License = License
 
     -- | A URL to the license used for the API.
   , _licenseUrl :: Maybe URL
+
+    -- | Specification Extensions
+  , _licenseExtensions :: SpecificationExtensions
   } deriving (Eq, Show, Generic, Data, Typeable)
 
 instance IsString License where
-  fromString s = License (fromString s) Nothing
+  fromString s = License (fromString s) Nothing mempty
 
 -- | An object representing a Server.
 data Server = Server
@@ -178,6 +191,8 @@ data Server = Server
     -- | A map between a variable name and its value.
     -- The value is used for substitution in the server's URL template.
   , _serverVariables :: InsOrdHashMap Text ServerVariable
+    -- | Specification Extensions
+  , _serverExtensions :: SpecificationExtensions
   } deriving (Eq, Show, Generic, Data, Typeable)
 
 data ServerVariable = ServerVariable
@@ -194,10 +209,13 @@ data ServerVariable = ServerVariable
     -- | An optional description for the server variable.
     -- [CommonMark syntax](https://spec.commonmark.org/) MAY be used for rich text representation.
   , _serverVariableDescription :: Maybe Text
+
+    -- | Specification Extensions
+  , _serverVariableExtensions :: SpecificationExtensions
   } deriving (Eq, Show, Generic, Data, Typeable)
 
 instance IsString Server where
-  fromString s = Server (fromString s) Nothing mempty
+  fromString s = Server (fromString s) Nothing mempty mempty
 
 -- | Holds a set of reusable objects for different aspects of the OAS.
 -- All objects defined within the components object will have no effect on the API
@@ -258,6 +276,9 @@ data PathItem = PathItem
     -- The list MUST NOT include duplicated parameters.
     -- A unique parameter is defined by a combination of a name and location.
   , _pathItemParameters :: [Referenced Param]
+
+    -- | Specification Extensions
+  , _pathItemExtensions :: SpecificationExtensions
   } deriving (Eq, Show, Generic, Data, Typeable)
 
 -- | Describes a single API operation on a path.
@@ -323,6 +344,9 @@ data Operation = Operation
     -- If an alternative server object is specified at the 'PathItem' Object or Root level,
     -- it will be overridden by this value.
   , _operationServers :: [Server]
+
+    -- | Specification Extensions
+  , _operationExtensions :: SpecificationExtensions
   } deriving (Eq, Show, Generic, Data, Typeable)
 
 -- This instance should be in @http-media@.
@@ -356,6 +380,9 @@ data RequestBody = RequestBody
     -- | Determines if the request body is required in the request.
     -- Defaults to 'False'.
   , _requestBodyRequired :: Maybe Bool
+
+    -- | Specification Extensions
+  , _requestBodyExtensions :: SpecificationExtensions
   } deriving (Eq, Show, Generic, Data, Typeable)
 
 -- | Each Media Type Object provides schema and examples for the media type identified by its key.
@@ -375,6 +402,8 @@ data MediaTypeObject = MediaTypeObject
     -- The encoding object SHALL only apply to 'RequestBody' objects when the media type
     -- is @multipart@ or @application/x-www-form-urlencoded@.
   , _mediaTypeObjectEncoding :: InsOrdHashMap Text Encoding
+    -- | Specification Extensions
+  , _mediaTypeObjectExtensions :: SpecificationExtensions
   } deriving (Eq, Show, Generic, Data, Typeable)
 
 -- | In order to support common ways of serializing simple parameters, a set of style values are defined.
@@ -438,6 +467,8 @@ data Encoding = Encoding
     -- The default value is @false@. This property SHALL be ignored if the request body media type
     -- is not @application/x-www-form-urlencoded@.
   , _encodingAllowReserved :: Maybe Bool
+    -- | Specification Extensions
+  , _encodingExtensions :: SpecificationExtensions
   } deriving (Eq, Show, Generic, Data, Typeable)
 
 newtype MimeList = MimeList { getMimeList :: [MediaType] }
@@ -523,6 +554,8 @@ data Param = Param
     -- the examples value SHALL override the example provided by the schema.
   , _paramExamples :: InsOrdHashMap Text (Referenced Example)
 
+  , _paramExtensions :: SpecificationExtensions
+
     -- TODO
     -- _paramContent :: InsOrdHashMap MediaType MediaTypeObject
     -- should be singleton. mutually exclusive with _paramSchema.
@@ -548,6 +581,9 @@ data Example = Example
     -- in JSON or YAML documents. The '_exampleValue' field
     -- and '_exampleExternalValue' field are mutually exclusive.
   , _exampleExternalValue :: Maybe URL
+
+    -- | Specification Extensions
+  , _exampleExtensions :: SpecificationExtensions
   } deriving (Eq, Show, Generic, Typeable, Data)
 
 data ExpressionOrValue
@@ -584,6 +620,9 @@ data Link = Link
 
     -- | A server object to be used by the target operation.
   , _linkServer :: Maybe Server
+
+    -- | Specification Extensions
+  , _linkExtensions :: SpecificationExtensions
   } deriving (Eq, Show, Generic, Typeable, Data)
 
 -- | Items for @'OpenApiArray'@ schemas.
@@ -621,7 +660,9 @@ data ParamLocation
   | ParamPath
     -- | Used to pass a specific cookie value to the API.
   | ParamCookie
-  deriving (Eq, Show, Generic, Data, Typeable)
+  deriving (Eq, Ord, Show, Generic, Data, Typeable)
+
+instance Hashable ParamLocation
 
 type Format = Text
 
@@ -673,6 +714,8 @@ data Schema = Schema
   , _schemaUniqueItems :: Maybe Bool
   , _schemaEnum :: Maybe [Value]
   , _schemaMultipleOf :: Maybe Scientific
+    -- | Specification Extensions
+  , _schemaExtensions :: SpecificationExtensions
   } deriving (Eq, Show, Generic, Data, Typeable)
 
 -- | Regex pattern for @string@ type.
@@ -719,6 +762,8 @@ data Xml = Xml
     -- Default value is @False@.
     -- The definition takes effect only when defined alongside type being array (outside the items).
   , _xmlWrapped :: Maybe Bool
+    -- | Specification Extensions
+  , _xmlExtensions :: SpecificationExtensions
   } deriving (Eq, Show, Generic, Data, Typeable)
 
 -- | A container for the expected responses of an operation.
@@ -734,6 +779,8 @@ data Responses = Responses
     -- | Any HTTP status code can be used as the property name (one property per HTTP status code).
     -- Describes the expected response for those HTTP status codes.
   , _responsesResponses :: InsOrdHashMap HttpStatusCode (Referenced Response)
+    -- | Specification Extensions
+  , _responsesExtensions :: SpecificationExtensions
   } deriving (Eq, Show, Generic, Data, Typeable)
 
 type HttpStatusCode = Int
@@ -757,10 +804,12 @@ data Response = Response
     -- The key of the map is a short name for the link, following the naming
     -- constraints of the names for 'Component' Objects.
   , _responseLinks :: InsOrdHashMap Text (Referenced Link)
+    -- | Specification Extensions
+  , _responseExtensions :: SpecificationExtensions
   } deriving (Eq, Show, Generic, Data, Typeable)
 
 instance IsString Response where
-  fromString s = Response (fromString s) mempty mempty mempty
+  fromString s = Response (fromString s) mempty mempty mempty mempty
 
 -- | A map of possible out-of band callbacks related to the parent operation.
 -- Each value in the map is a 'PathItem' Object that describes a set of requests that
@@ -787,6 +836,7 @@ data Header = Header
   , _headerExamples :: InsOrdHashMap Text (Referenced Example)
 
   , _headerSchema :: Maybe (Referenced Schema)
+  , _headerExtensions :: SpecificationExtensions
   } deriving (Eq, Show, Generic, Data, Typeable)
 
 -- | The location of the API key.
@@ -837,6 +887,8 @@ data OAuth2Flow p = OAuth2Flow
     -- A map between the scope name and a short description for it.
     -- The map MAY be empty.
   , _oAuth2Scopes :: InsOrdHashMap Text Text
+    -- | Specification Extensions
+  , _oAuth2Extensions :: SpecificationExtensions
   } deriving (Eq, Show, Generic, Data, Typeable)
 
 data OAuth2Flows = OAuth2Flows
@@ -851,6 +903,8 @@ data OAuth2Flows = OAuth2Flows
 
     -- | Configuration for the OAuth Authorization Code flow
   , _oAuth2FlowsAuthorizationCode :: Maybe (OAuth2Flow OAuth2AuthorizationCodeFlow)
+    -- | Specification Extensions
+  , _oAuth2FlowsExtensions :: SpecificationExtensions
   } deriving (Eq, Show, Generic, Data, Typeable)
 
 type BearerFormat = Text
@@ -908,6 +962,9 @@ data SecurityScheme = SecurityScheme
 
     -- | A short description for security scheme.
   , _securitySchemeDescription :: Maybe Text
+
+   -- | Specification Extensions
+  , _securitySchemeExtensions :: SpecificationExtensions
   } deriving (Eq, Show, Generic, Data, Typeable)
 
 newtype SecurityDefinitions
@@ -936,12 +993,15 @@ data Tag = Tag
 
     -- | Additional external documentation for this tag.
   , _tagExternalDocs :: Maybe ExternalDocs
-  } deriving (Eq, Ord, Show, Generic, Data, Typeable)
+
+    -- | Specification Extensions
+  , _tagExtensions :: SpecificationExtensions
+  } deriving (Eq, Show, Generic, Data, Typeable)
 
 instance Hashable Tag
 
 instance IsString Tag where
-  fromString s = Tag (fromString s) Nothing Nothing
+  fromString s = Tag (fromString s) Nothing Nothing mempty
 
 -- | Allows referencing an external resource for extended documentation.
 data ExternalDocs = ExternalDocs
@@ -951,7 +1011,10 @@ data ExternalDocs = ExternalDocs
 
     -- | The URL for the target documentation.
   , _externalDocsUrl :: URL
-  } deriving (Eq, Ord, Show, Generic, Data, Typeable)
+
+    -- | Specification Extensions
+  , _externalDocsExtensions :: SpecificationExtensions
+  } deriving (Eq, Show, Generic, Data, Typeable)
 
 instance Hashable ExternalDocs
 
@@ -968,15 +1031,23 @@ data Referenced a
 instance IsString a => IsString (Referenced a) where
   fromString = Inline . fromString
 
-newtype URL = URL { getUrl :: Text } deriving (Eq, Ord, Show, Hashable, ToJSON, FromJSON, Data, Typeable)
+newtype URL = URL { getUrl :: Text }
+  deriving (Eq, Ord, Show, Hashable, ToJSON, FromJSON, Data, Typeable, AesonDefaultValue)
 
 data AdditionalProperties
   = AdditionalPropertiesAllowed Bool
   | AdditionalPropertiesSchema (Referenced Schema)
   deriving (Eq, Show, Data, Typeable)
 
+
 newtype OpenApiSpecVersion = OpenApiSpecVersion {getVersion :: Version} deriving (Eq, Show, Generic, Data, Typeable)
 
+newtype SpecificationExtensions = SpecificationExtensions { _unDefs :: Definitions Value}
+  deriving (Eq, Show, Hashable, Data, Typeable, Semigroup, Monoid, SwaggerMonoid)
+
+instance AesonDefaultValue SpecificationExtensions where
+  defaultValue = Just (SpecificationExtensions mempty)
+
 -------------------------------------------------------------------------------
 -- Generic instances
 -------------------------------------------------------------------------------
@@ -1000,18 +1071,25 @@ deriveGeneric ''Example
 deriveGeneric ''Encoding
 deriveGeneric ''Link
 deriveGeneric ''OpenApiSpecVersion
+deriveGeneric ''Info
+deriveGeneric ''Contact
+deriveGeneric ''License
+deriveGeneric ''ServerVariable
+deriveGeneric ''Tag
+deriveGeneric ''Xml
+deriveGeneric ''ExternalDocs
 
 -- =======================================================================
 -- Monoid instances
 -- =======================================================================
 
 instance Semigroup OpenApiSpecVersion where
-  (<>) (OpenApiSpecVersion a) (OpenApiSpecVersion b) = OpenApiSpecVersion $ max a b 
-  
+  (<>) (OpenApiSpecVersion a) (OpenApiSpecVersion b) = OpenApiSpecVersion $ max a b
+
 instance Monoid OpenApiSpecVersion where
   mempty = OpenApiSpecVersion (makeVersion [3,0,0])
   mappend = (<>)
-  
+
 instance Semigroup OpenApi where
   (<>) = genericMappend
 instance Monoid OpenApi where
@@ -1108,6 +1186,7 @@ instance Semigroup OAuth2Flows where
     , _oAuth2FlowsPassword = _oAuth2FlowsPassword l <> _oAuth2FlowsPassword r
     , _oAuth2FlowsClientCredentials = _oAuth2FlowsClientCredentials l <> _oAuth2FlowsClientCredentials r
     , _oAuth2FlowsAuthorizationCode = _oAuth2FlowsAuthorizationCode l <> _oAuth2FlowsAuthorizationCode r
+    , _oAuth2FlowsExtensions = _oAuth2FlowsExtensions l <> _oAuth2FlowsExtensions r
     }
 
 instance Monoid OAuth2Flows where
@@ -1115,9 +1194,9 @@ instance Monoid OAuth2Flows where
   mappend = (<>)
 
 instance Semigroup SecurityScheme where
-  SecurityScheme (SecuritySchemeOAuth2 lFlows) lDesc
-    <> SecurityScheme (SecuritySchemeOAuth2 rFlows) rDesc =
-      SecurityScheme (SecuritySchemeOAuth2 $ lFlows <> rFlows) (swaggerMappend lDesc rDesc)
+  SecurityScheme (SecuritySchemeOAuth2 lFlows) lDesc lExt
+    <> SecurityScheme (SecuritySchemeOAuth2 rFlows) rDesc rExt =
+      SecurityScheme (SecuritySchemeOAuth2 $ lFlows <> rFlows) (swaggerMappend lDesc rDesc) (lExt <> rExt)
   l <> _ = l
 
 instance Semigroup SecurityDefinitions where
@@ -1184,33 +1263,12 @@ instance ToJSON OpenApiType where
 instance ToJSON ParamLocation where
   toJSON = genericToJSON (jsonPrefix "Param")
 
-instance ToJSON Info where
-  toJSON = genericToJSON (jsonPrefix "Info")
-
-instance ToJSON Contact where
-  toJSON = genericToJSON (jsonPrefix "Contact")
-
-instance ToJSON License where
-  toJSON = genericToJSON (jsonPrefix "License")
-
-instance ToJSON ServerVariable where
-  toJSON = genericToJSON (jsonPrefix "ServerVariable")
-
 instance ToJSON ApiKeyLocation where
   toJSON = genericToJSON (jsonPrefix "ApiKey")
 
 instance ToJSON ApiKeyParams where
   toJSON = genericToJSON (jsonPrefix "apiKey")
 
-instance ToJSON Tag where
-  toJSON = genericToJSON (jsonPrefix "Tag")
-
-instance ToJSON ExternalDocs where
-  toJSON = genericToJSON (jsonPrefix "ExternalDocs")
-
-instance ToJSON Xml where
-  toJSON = genericToJSON (jsonPrefix "Xml")
-
 instance ToJSON Discriminator where
   toJSON = genericToJSON (jsonPrefix "Discriminator")
 
@@ -1239,30 +1297,12 @@ instance FromJSON OpenApiType where
 instance FromJSON ParamLocation where
   parseJSON = genericParseJSON (jsonPrefix "Param")
 
-instance FromJSON Info where
-  parseJSON = genericParseJSON (jsonPrefix "Info")
-
-instance FromJSON Contact where
-  parseJSON = genericParseJSON (jsonPrefix "Contact")
-
-instance FromJSON License where
-  parseJSON = genericParseJSON (jsonPrefix "License")
-
-instance FromJSON ServerVariable where
-  parseJSON = genericParseJSON (jsonPrefix "ServerVariable")
-
 instance FromJSON ApiKeyLocation where
   parseJSON = genericParseJSON (jsonPrefix "ApiKey")
 
 instance FromJSON ApiKeyParams where
   parseJSON = genericParseJSON (jsonPrefix "apiKey")
 
-instance FromJSON Tag where
-  parseJSON = genericParseJSON (jsonPrefix "Tag")
-
-instance FromJSON ExternalDocs where
-  parseJSON = genericParseJSON (jsonPrefix "ExternalDocs")
-
 instance FromJSON Discriminator where
   parseJSON = genericParseJSON (jsonPrefix "Discriminator")
 
@@ -1282,7 +1322,7 @@ instance FromJSON OAuth2AuthorizationCodeFlow where
 -- Manual ToJSON instances
 -- =======================================================================
 
-instance ToJSON OpenApiSpecVersion where 
+instance ToJSON OpenApiSpecVersion where
   toJSON (OpenApiSpecVersion v)= toJSON . showVersion $ v
 
 instance ToJSON MediaType where
@@ -1346,7 +1386,7 @@ instance ToJSON SecurityScheme where
 
 instance ToJSON Schema where
   toJSON = sopSwaggerGenericToJSONWithOpts $
-      mkSwaggerAesonOptions "schema" & saoSubObject ?~ "items"
+      mkSwaggerAesonOptions "schema" & saoSubObject .~ ["items", "extensions"]
 
 instance ToJSON Header where
   toJSON = sopSwaggerGenericToJSON
@@ -1448,6 +1488,32 @@ instance ToJSON ExpressionOrValue where
 instance ToJSON Callback where
   toJSON (Callback ps) = toJSON ps
 
+instance ToJSON SpecificationExtensions where
+  toJSON = toJSON . addExtPrefix . _unDefs
+    where
+      addExtPrefix = InsOrdHashMap.mapKeys ("x-" <>)
+
+instance ToJSON Info where
+  toJSON = sopSwaggerGenericToJSONWithOpts (mkSwaggerAesonOptions "Info")
+
+instance ToJSON Contact where
+  toJSON = sopSwaggerGenericToJSONWithOpts (mkSwaggerAesonOptions "Contact")
+
+instance ToJSON License where
+  toJSON = sopSwaggerGenericToJSONWithOpts (mkSwaggerAesonOptions "License")
+
+instance ToJSON ServerVariable where
+  toJSON = sopSwaggerGenericToJSONWithOpts (mkSwaggerAesonOptions "ServerVariable")
+
+instance ToJSON Tag where
+  toJSON = sopSwaggerGenericToJSONWithOpts (mkSwaggerAesonOptions "Tag")
+
+instance ToJSON ExternalDocs where
+  toJSON = sopSwaggerGenericToJSONWithOpts (mkSwaggerAesonOptions "ExternalDocs")
+
+instance ToJSON Xml where
+  toJSON = sopSwaggerGenericToJSONWithOpts (mkSwaggerAesonOptions "Xml")
+
 -- =======================================================================
 -- Manual FromJSON instances
 -- =======================================================================
@@ -1456,15 +1522,15 @@ instance FromJSON OpenApiSpecVersion where
   parseJSON = withText "OpenApiSpecVersion" $ \str ->
             let validatedVersion :: Either String Version
                 validatedVersion = do
-                  parsedVersion <- readVersion str 
+                  parsedVersion <- readVersion str
                   unless ((parsedVersion >= lowerOpenApiSpecVersion) && (parsedVersion <= upperOpenApiSpecVersion)) $
                      Left ("The provided version " <> showVersion parsedVersion <> " is out of the allowed range >=" <> showVersion lowerOpenApiSpecVersion <> " && <=" <> showVersion upperOpenApiSpecVersion)
                   return parsedVersion
-             in 
+             in
               either fail (return . OpenApiSpecVersion) validatedVersion
     where
     readVersion :: Text -> Either String Version
-    readVersion v = case readP_to_S parseVersion (Text.unpack v) of 
+    readVersion v = case readP_to_S parseVersion (Text.unpack v) of
       [] -> Left $ "Failed to parse as a version string " <> Text.unpack v
       solutions -> Right (fst . last $ solutions)
 
@@ -1538,9 +1604,22 @@ instance FromJSON Param where
 instance FromJSON Responses where
   parseJSON (Object o) = Responses
     <$> o .:? "default"
-    <*> parseJSON (Object (deleteKey "default" o))
+    <*> parseJSON
+      ( Object
+        ( filterKeys (not . isExt . keyToText) $
+          deleteKey "default" o
+        )
+      )
+    <*> case filterKeys (isExt . keyToText) o of
+          exts
+            | null exts -> pure (SpecificationExtensions mempty)
+            | otherwise -> parseJSON (Object exts)
+
   parseJSON _ = empty
 
+isExt :: Text -> Bool
+isExt = Text.isPrefixOf "x-"
+
 instance FromJSON Example where
   parseJSON = sopSwaggerGenericParseJSON
 
@@ -1594,9 +1673,6 @@ instance FromJSON (Referenced Header)   where parseJSON = referencedParseJSON "#
 instance FromJSON (Referenced Link)     where parseJSON = referencedParseJSON "#/components/links/"
 instance FromJSON (Referenced Callback) where parseJSON = referencedParseJSON "#/components/callbacks/"
 
-instance FromJSON Xml where
-  parseJSON = genericParseJSON (jsonPrefix "xml")
-
 instance FromJSON AdditionalProperties where
   parseJSON (Bool b) = pure $ AdditionalPropertiesAllowed b
   parseJSON js = AdditionalPropertiesSchema <$> parseJSON js
@@ -1609,49 +1685,98 @@ instance FromJSON ExpressionOrValue where
 instance FromJSON Callback where
   parseJSON = fmap Callback . parseJSON
 
+instance FromJSON SpecificationExtensions where
+  parseJSON = withObject "SpecificationExtensions" extFieldsParser
+    where
+      extFieldsParser = pure . SpecificationExtensions . InsOrdHashMap.fromList . catMaybes . filterExtFields
+      filterExtFields = fmap (\(k, v) -> (, v) <$> Text.stripPrefix "x-" (keyToText k)) . objectToList
+
+instance FromJSON Info where
+  parseJSON = sopSwaggerGenericParseJSONWithOpts (mkSwaggerAesonOptions "Info")
+
+instance FromJSON Contact where
+  parseJSON = sopSwaggerGenericParseJSONWithOpts (mkSwaggerAesonOptions "Contact")
+
+instance FromJSON License where
+  parseJSON = sopSwaggerGenericParseJSONWithOpts (mkSwaggerAesonOptions "License")
+
+instance FromJSON ServerVariable where
+  parseJSON = sopSwaggerGenericParseJSONWithOpts (mkSwaggerAesonOptions "ServerVariable")
+
+instance FromJSON Tag where
+  parseJSON = sopSwaggerGenericParseJSONWithOpts (mkSwaggerAesonOptions "Tag")
+
+instance FromJSON ExternalDocs where
+  parseJSON = sopSwaggerGenericParseJSONWithOpts (mkSwaggerAesonOptions "ExternalDocs")
+
+instance FromJSON Xml where
+  parseJSON = sopSwaggerGenericParseJSONWithOpts (mkSwaggerAesonOptions "xml")
+
 instance HasSwaggerAesonOptions Server where
   swaggerAesonOptions _ = mkSwaggerAesonOptions "server"
 instance HasSwaggerAesonOptions Components where
   swaggerAesonOptions _ = mkSwaggerAesonOptions "components"
 instance HasSwaggerAesonOptions Header where
-  swaggerAesonOptions _ = mkSwaggerAesonOptions "header"
+  swaggerAesonOptions _ = mkSwaggerAesonOptions "header" & saoSubObject .~ ["extensions"]
 instance AesonDefaultValue p => HasSwaggerAesonOptions (OAuth2Flow p) where
-  swaggerAesonOptions _ = mkSwaggerAesonOptions "oauth2" & saoSubObject ?~ "params"
+  swaggerAesonOptions _ = mkSwaggerAesonOptions "oauth2" & saoSubObject .~ ["params", "extensions"]
 instance HasSwaggerAesonOptions OAuth2Flows where
-  swaggerAesonOptions _ = mkSwaggerAesonOptions "oauth2Flows"
+  swaggerAesonOptions _ = mkSwaggerAesonOptions "oauth2Flows" & saoSubObject .~ ["extensions"]
 instance HasSwaggerAesonOptions Operation where
-  swaggerAesonOptions _ = mkSwaggerAesonOptions "operation"
+  swaggerAesonOptions _ = mkSwaggerAesonOptions "operation" & saoSubObject .~ ["extensions"]
 instance HasSwaggerAesonOptions Param where
-  swaggerAesonOptions _ = mkSwaggerAesonOptions "param"
+  swaggerAesonOptions _ = mkSwaggerAesonOptions "param" & saoSubObject .~ ["extensions"]
 instance HasSwaggerAesonOptions PathItem where
-  swaggerAesonOptions _ = mkSwaggerAesonOptions "pathItem"
+  swaggerAesonOptions _ = mkSwaggerAesonOptions "pathItem" & saoSubObject .~ ["extensions"]
 instance HasSwaggerAesonOptions Response where
-  swaggerAesonOptions _ = mkSwaggerAesonOptions "response"
+  swaggerAesonOptions _ = mkSwaggerAesonOptions "response" & saoSubObject .~ ["extensions"]
 instance HasSwaggerAesonOptions RequestBody where
-  swaggerAesonOptions _ = mkSwaggerAesonOptions "requestBody"
+  swaggerAesonOptions _ = mkSwaggerAesonOptions "requestBody" & saoSubObject .~ ["extensions"]
 instance HasSwaggerAesonOptions MediaTypeObject where
-  swaggerAesonOptions _ = mkSwaggerAesonOptions "mediaTypeObject"
+  swaggerAesonOptions _ = mkSwaggerAesonOptions "mediaTypeObject" & saoSubObject .~ ["extensions"]
 instance HasSwaggerAesonOptions Responses where
-  swaggerAesonOptions _ = mkSwaggerAesonOptions "responses" & saoSubObject ?~ "responses"
+  swaggerAesonOptions _ = mkSwaggerAesonOptions "responses" & saoSubObject .~ ["responses", "extensions"]
 instance HasSwaggerAesonOptions SecurityScheme where
-  swaggerAesonOptions _ = mkSwaggerAesonOptions "securityScheme" & saoSubObject ?~ "type"
+  swaggerAesonOptions _ = mkSwaggerAesonOptions "securityScheme" & saoSubObject .~ ["type", "extensions"]
 instance HasSwaggerAesonOptions Schema where
-  swaggerAesonOptions _ = mkSwaggerAesonOptions "schema" & saoSubObject ?~ "paramSchema"
+  swaggerAesonOptions _ = mkSwaggerAesonOptions "schema" & saoSubObject .~ ["paramSchema", "extensions"]
 instance HasSwaggerAesonOptions OpenApiSpecVersion where
   swaggerAesonOptions _ = mkSwaggerAesonOptions "openapi"
 instance HasSwaggerAesonOptions OpenApi where
-  swaggerAesonOptions _ = mkSwaggerAesonOptions "swagger"
+  swaggerAesonOptions _ = mkSwaggerAesonOptions "swagger" & saoSubObject .~ ["extensions"]
 instance HasSwaggerAesonOptions Example where
-  swaggerAesonOptions _ = mkSwaggerAesonOptions "example"
+  swaggerAesonOptions _ = mkSwaggerAesonOptions "example" & saoSubObject .~ ["extensions"]
 instance HasSwaggerAesonOptions Encoding where
-  swaggerAesonOptions _ = mkSwaggerAesonOptions "encoding"
+  swaggerAesonOptions _ = mkSwaggerAesonOptions "encoding" & saoSubObject .~ ["extensions"]
 
 instance HasSwaggerAesonOptions Link where
-  swaggerAesonOptions _ = mkSwaggerAesonOptions "link"
+  swaggerAesonOptions _ = mkSwaggerAesonOptions "link" & saoSubObject .~ ["extensions"]
 
-instance AesonDefaultValue Version where 
+instance AesonDefaultValue Version where
   defaultValue = Just (makeVersion [3,0,0])
 instance AesonDefaultValue OpenApiSpecVersion
+
+instance HasSwaggerAesonOptions Info where
+  swaggerAesonOptions _ = mkSwaggerAesonOptions "info" & saoSubObject .~ ["extensions"]
+
+instance HasSwaggerAesonOptions Contact where
+  swaggerAesonOptions _ = mkSwaggerAesonOptions "contact" & saoSubObject .~ ["extensions"]
+
+instance HasSwaggerAesonOptions License where
+  swaggerAesonOptions _ = mkSwaggerAesonOptions "license" & saoSubObject .~ ["extensions"]
+
+instance HasSwaggerAesonOptions ServerVariable where
+  swaggerAesonOptions _ = mkSwaggerAesonOptions "serverVariable" & saoSubObject .~ ["extensions"]
+
+instance HasSwaggerAesonOptions Tag where
+  swaggerAesonOptions _ = mkSwaggerAesonOptions "tag" & saoSubObject .~ ["extensions"]
+
+instance HasSwaggerAesonOptions Xml where
+  swaggerAesonOptions _ = mkSwaggerAesonOptions "xml" & saoSubObject .~ ["extensions"]
+
+instance HasSwaggerAesonOptions ExternalDocs where
+  swaggerAesonOptions _ = mkSwaggerAesonOptions "externalDocs" & saoSubObject .~ ["extensions"]
+
 instance AesonDefaultValue Server
 instance AesonDefaultValue Components
 instance AesonDefaultValue OAuth2ImplicitFlow
diff --git a/src/Data/OpenApi/Internal/AesonUtils.hs b/src/Data/OpenApi/Internal/AesonUtils.hs
index 3804ab32..70e9cc34 100644
--- a/src/Data/OpenApi/Internal/AesonUtils.hs
+++ b/src/Data/OpenApi/Internal/AesonUtils.hs
@@ -12,6 +12,7 @@ module Data.OpenApi.Internal.AesonUtils (
     sopSwaggerGenericToEncoding,
     sopSwaggerGenericToJSONWithOpts,
     sopSwaggerGenericParseJSON,
+    sopSwaggerGenericParseJSONWithOpts,
     -- * Options
     HasSwaggerAesonOptions(..),
     SwaggerAesonOptions,
@@ -49,13 +50,13 @@ import Data.OpenApi.Aeson.Compat (keyToString, objectToList, stringToKey)
 data SwaggerAesonOptions = SwaggerAesonOptions
     { _saoPrefix          :: String
     , _saoAdditionalPairs :: [Pair]
-    , _saoSubObject       :: Maybe String
+    , _saoSubObject       :: [String]
     }
 
 mkSwaggerAesonOptions
     :: String  -- ^ prefix
     -> SwaggerAesonOptions
-mkSwaggerAesonOptions pfx = SwaggerAesonOptions pfx [] Nothing
+mkSwaggerAesonOptions pfx = SwaggerAesonOptions pfx [] []
 
 makeLenses ''SwaggerAesonOptions
 
@@ -154,7 +155,7 @@ sopSwaggerGenericToJSON'' (SwaggerAesonOptions prefix _ sub) = go
     go :: (All ToJSON ys, All Eq ys) => NP I ys -> NP FieldInfo ys -> NP Maybe ys -> [Pair]
     go  Nil Nil Nil = []
     go (I x :* xs) (FieldInfo name :* names) (def :* defs)
-        | Just name' == sub = case json of
+        | name' `elem` sub = case json of
               Object m -> objectToList m ++ rest
               Null     -> rest
               _        -> error $ "sopSwaggerGenericToJSON: subjson is not an object: " ++ show json
@@ -176,8 +177,7 @@ sopSwaggerGenericToJSON'' (SwaggerAesonOptions prefix _ sub) = go
 -------------------------------------------------------------------------------
 -- FromJSON
 -------------------------------------------------------------------------------
-
-sopSwaggerGenericParseJSON
+sopSwaggerGenericParseJSONWithOpts
     :: forall a xs.
         ( HasDatatypeInfo a
         , HasSwaggerAesonOptions a
@@ -185,13 +185,37 @@ sopSwaggerGenericParseJSON
         , All2 Eq (Code a)
         , Code a ~ '[xs]
         )
-    => Value
+    => SwaggerAesonOptions
+    -> Value
     -> Parser a
-sopSwaggerGenericParseJSON = withObject "Swagger Record Object" $ \obj ->
+sopSwaggerGenericParseJSONWithOpts opts = withObject "Swagger Record Object" $ \obj ->
     let ps = sopSwaggerGenericParseJSON' opts obj (datatypeInfo proxy) (aesonDefaults proxy)
     in do
         traverse_ (parseAdditionalField obj) (opts ^. saoAdditionalPairs)
         to <$> ps
+  where
+    proxy = Proxy :: Proxy a
+
+    parseAdditionalField :: Object -> Pair -> Parser ()
+    parseAdditionalField obj (k, v) = do
+        v' <- obj .: k
+        unless (v == v') $ fail $
+            "Additonal field don't match for key " ++ keyToString k
+            ++ ": " ++ show v
+            ++ " /= " ++ show v'
+
+
+sopSwaggerGenericParseJSON
+    :: forall a xs.
+        ( HasDatatypeInfo a
+        , HasSwaggerAesonOptions a
+        , All2 FromJSON (Code a)
+        , All2 Eq (Code a)
+        , Code a ~ '[xs]
+        )
+    => Value
+    -> Parser a
+sopSwaggerGenericParseJSON = sopSwaggerGenericParseJSONWithOpts opts
   where
     proxy = Proxy :: Proxy a
     opts  = swaggerAesonOptions proxy
@@ -227,9 +251,9 @@ sopSwaggerGenericParseJSON'' (SwaggerAesonOptions prefix _ sub) obj = go
     go :: (All FromJSON ys, All Eq ys) => NP FieldInfo ys -> NP Maybe ys -> Parser (NP I ys)
     go  Nil Nil = pure Nil
     go (FieldInfo name :* names) (def :* defs)
-        | Just name' == sub =
+        | name' `elem` sub =
             -- Note: we might strip fields of outer structure.
-            cons <$> (withDef $ parseJSON $ Object obj) <*> rest
+            cons <$> withDef (parseJSON $ Object obj) <*> rest
         | otherwise = case def of
             Just def' -> cons <$> obj .:? stringToKey name' .!= def' <*> rest
             Nothing  ->  cons <$> obj .: stringToKey name' <*> rest
@@ -269,7 +293,7 @@ sopSwaggerGenericToEncoding x =
     opts  = swaggerAesonOptions proxy
 
 pairsToSeries :: [Pair] -> Series
-pairsToSeries = foldMap (\(k, v) -> (k .= v))
+pairsToSeries = foldMap (uncurry (.=))
 
 sopSwaggerGenericToEncoding'
     :: (All2 ToJSON '[xs], All2 Eq '[xs])
@@ -294,7 +318,7 @@ sopSwaggerGenericToEncoding'' (SwaggerAesonOptions prefix _ sub) = go
     go :: (All ToJSON ys, All Eq ys) => NP I ys -> NP FieldInfo ys -> NP Maybe ys -> Series
     go  Nil Nil Nil = mempty
     go (I x :* xs) (FieldInfo name :* names) (def :* defs)
-        | Just name' == sub = case toJSON x of
+        | name' `elem` sub = case toJSON x of
               Object m -> pairsToSeries (objectToList m) <> rest
               Null     -> rest
               _        -> error $ "sopSwaggerGenericToJSON: subjson is not an object: " ++ show (toJSON x)
@@ -311,3 +335,21 @@ sopSwaggerGenericToEncoding'' (SwaggerAesonOptions prefix _ sub) = go
     modifier = lowerFirstUppers . drop (length prefix)
     lowerFirstUppers s = map toLower x ++ y
       where (x, y) = span isUpper s
+
+sopSwaggerGenericToEncodingWithOpts
+    :: forall a xs.
+        ( HasDatatypeInfo a
+        , HasSwaggerAesonOptions a
+        , All2 ToJSON (Code a)
+        , All2 Eq (Code a)
+        , Code a ~ '[xs]
+        )
+    => SwaggerAesonOptions
+    -> a
+    -> Encoding
+sopSwaggerGenericToEncodingWithOpts opts x =
+    let ps = sopSwaggerGenericToEncoding' opts (from x) (datatypeInfo proxy) defs
+    in pairs (pairsToSeries (opts ^. saoAdditionalPairs) <> ps)
+  where
+    proxy = Proxy :: Proxy a
+    defs = hcpure (Proxy :: Proxy AesonDefaultValue) defaultValue
diff --git a/src/Data/OpenApi/Lens.hs b/src/Data/OpenApi/Lens.hs
index b8e23101..a434ca06 100644
--- a/src/Data/OpenApi/Lens.hs
+++ b/src/Data/OpenApi/Lens.hs
@@ -57,6 +57,7 @@ makeFields ''Encoding
 makeFields ''Example
 makeFields ''Discriminator
 makeFields ''Link
+makeLenses ''SpecificationExtensions
 
 -- * Prisms
 -- ** 'SecuritySchemeType' prisms
@@ -89,9 +90,11 @@ _OpenApiItemsObject
 
 type instance Index Responses = HttpStatusCode
 type instance Index Operation = HttpStatusCode
+type instance Index SpecificationExtensions = Text
 
 type instance IxValue Responses = Referenced Response
 type instance IxValue Operation = Referenced Response
+type instance IxValue SpecificationExtensions = Value
 
 instance Ixed Responses where ix n = responses . ix n
 instance At   Responses where at n = responses . at n
@@ -99,6 +102,9 @@ instance At   Responses where at n = responses . at n
 instance Ixed Operation where ix n = responses . ix n
 instance At   Operation where at n = responses . at n
 
+instance Ixed SpecificationExtensions where ix n = unDefs . ix n
+instance At   SpecificationExtensions where at n = unDefs . at n
+
 instance HasType NamedSchema (Maybe OpenApiType) where type_ = schema.type_
 
 -- OVERLAPPABLE instances
diff --git a/stack.yaml.lock b/stack.yaml.lock
new file mode 100644
index 00000000..4cf8f146
--- /dev/null
+++ b/stack.yaml.lock
@@ -0,0 +1,47 @@
+# This file was autogenerated by Stack.
+# You should not edit this file by hand.
+# For more information, please see the documentation at:
+#   https://docs.haskellstack.org/en/stable/lock_files
+
+packages:
+- completed:
+    hackage: optics-core-0.3@sha256:0464583aaef715f8e48b8c9ce3fab9866345de93e740dae32d5c5e9a57097bf7,4532
+    pantry-tree:
+      size: 5030
+      sha256: d87366c3a2d4099a7a1d54df029a38e24b591ba8fb88d56fabf0c5c4bc345a51
+  original:
+    hackage: optics-core-0.3
+- completed:
+    hackage: optics-th-0.3@sha256:b4746b3d142feb2dc9dfcf76b49a11fd04321aa0ee9c1bcd297c5e8dc393803c,1965
+    pantry-tree:
+      size: 653
+      sha256: 24e990405793450726f6364034614c715537b0ed3f21fafc9ce0267979feb01b
+  original:
+    hackage: optics-th-0.3
+- completed:
+    hackage: optics-extra-0.3@sha256:99696d87a92025e5f8d02e418b7851115e30a3d1425fba4afb6d41a0445cddd5,3492
+    pantry-tree:
+      size: 1809
+      sha256: 4d07622a2f3f62882de4f431d7f600053a8b461d5aa372c7ae596b672efab644
+  original:
+    hackage: optics-extra-0.3
+- completed:
+    hackage: indexed-profunctors-0.1@sha256:ddf618d0d4c58319c1e735e746bc69a1021f13b6f475dc9614b80af03432e6d4,1016
+    pantry-tree:
+      size: 235
+      sha256: cfd66c0a53be1b45eae72df112ea1158614458bb7b1c9cbbe3410b04ab011ec6
+  original:
+    hackage: indexed-profunctors-0.1
+- completed:
+    hackage: insert-ordered-containers-0.2.3.1@sha256:003307d51ba47411ead1f79b8559569b220723aea7439341d16980213f7520e9,2324
+    pantry-tree:
+      size: 541
+      sha256: c5b7b2a76cb090a990e9abbc671cb8913859925f230cd37ab1691ddca301fe06
+  original:
+    hackage: insert-ordered-containers-0.2.3.1
+snapshots:
+- completed:
+    size: 534126
+    url: https://raw.githubusercontent.com/commercialhaskell/stackage-snapshots/master/lts/16/31.yaml
+    sha256: 637fb77049b25560622a224845b7acfe81a09fdb6a96a3c75997a10b651667f6
+  original: lts-16.31
diff --git a/test/Data/OpenApiSpec.hs b/test/Data/OpenApiSpec.hs
index cb860747..7965aa33 100644
--- a/test/Data/OpenApiSpec.hs
+++ b/test/Data/OpenApiSpec.hs
@@ -2,6 +2,7 @@
 {-# LANGUAGE OverloadedStrings #-}
 {-# LANGUAGE ScopedTypeVariables #-}
 {-# LANGUAGE QuasiQuotes #-}
+{-# LANGUAGE LambdaCase #-}
 module Data.OpenApiSpec where
 
 import Prelude ()
@@ -15,9 +16,10 @@ import Data.HashMap.Strict (HashMap)
 import qualified Data.HashSet.InsOrd as InsOrdHS
 import Data.Text (Text)
 
-import Data.OpenApi
 import SpecCommon
 import Test.Hspec hiding (example)
+import qualified Data.HashMap.Strict.InsOrd as InsOrdHM
+import Data.OpenApi
 
 spec :: Spec
 spec = do
@@ -46,7 +48,7 @@ spec = do
     context "Todo Example" $ swaggerExample <=> swaggerExampleJSON
     context "PetStore Example" $ do
       it "decodes successfully" $ do
-        fromJSON petstoreExampleJSON `shouldSatisfy` (\x -> case x of Success (_ :: OpenApi) -> True; _ -> False)
+        fromJSON petstoreExampleJSON `shouldSatisfy` (\case Success (_ :: OpenApi) -> True; _ -> False)
       it "roundtrips: fmap toJSON . fromJSON" $ do
         (toJSON :: OpenApi -> Value) <$> fromJSON petstoreExampleJSON `shouldBe` Success petstoreExampleJSON
     context "Security schemes" $ do
@@ -140,18 +142,20 @@ operationExample = mempty
     & description ?~ "ID of pet that needs to be updated"
     & required ?~ True
     & in_ .~ ParamPath
-    & schema ?~ Inline (mempty & type_ ?~ OpenApiString))]
+    & schema ?~ Inline (mempty & type_ ?~ OpenApiString)
+    & extensions .~ SpecificationExtensions (InsOrdHM.fromList [("param-extension-here", "SomeString")]))]
   & requestBody ?~ Inline (
-    mempty & content . at "application/x-www-form-urlencoded" ?~ (mempty & schema ?~ (Inline (mempty
+    mempty & content . at "application/x-www-form-urlencoded" ?~ (mempty & schema ?~ Inline (mempty
       & properties . at "petId" ?~ Inline (mempty
         & description ?~ "Updated name of the pet"
         & type_ ?~ OpenApiString)
       & properties . at "status" ?~ Inline (mempty
         & description ?~ "Updated status of the pet"
-        & type_ ?~ OpenApiString)))))
+        & type_ ?~ OpenApiString))))
   & at 200 ?~ "Pet updated."
   & at 405 ?~ "Invalid input"
   & security .~ [SecurityRequirement [("petstore_auth", ["write:pets", "read:pets"])]]
+  & extensions .~ SpecificationExtensions (InsOrdHM.fromList [("ext1", toJSON True)])
 
 operationExampleJSON :: Value
 operationExampleJSON = [aesonQQ|
@@ -170,7 +174,8 @@ operationExampleJSON = [aesonQQ|
       },
       "in": "path",
       "name": "petId",
-      "description": "ID of pet that needs to be updated"
+      "description": "ID of pet that needs to be updated",
+      "x-param-extension-here": "SomeString"
     }
   ],
   "requestBody": {
@@ -206,7 +211,8 @@ operationExampleJSON = [aesonQQ|
         "read:pets"
       ]
     }
-  ]
+  ],
+ "x-ext1": true
 }
 |]
 
@@ -238,6 +244,7 @@ schemaSimpleModelExample = mempty
             & minimum_ ?~ 0
             & type_    ?~ OpenApiInteger
             & format   ?~ "int32" ) ]
+  & extensions .~ SpecificationExtensions (InsOrdHM.fromList [("ext1", toJSON True)])
 
 schemaSimpleModelExampleJSON :: Value
 schemaSimpleModelExampleJSON = [aesonQQ|
@@ -255,7 +262,8 @@ schemaSimpleModelExampleJSON = [aesonQQ|
       "type": "integer"
     }
   },
-  "type": "object"
+  "type": "object",
+  "x-ext1": true
 }
 |]
 
@@ -456,15 +464,18 @@ securityDefinitionsExample :: SecurityDefinitions
 securityDefinitionsExample = SecurityDefinitions
   [ ("api_key", SecurityScheme
       { _securitySchemeType = SecuritySchemeApiKey (ApiKeyParams "api_key" ApiKeyHeader)
-      , _securitySchemeDescription = Nothing })
+      , _securitySchemeDescription = Nothing
+      , _securitySchemeExtensions = mempty })
   , ("petstore_auth", SecurityScheme
       { _securitySchemeType = SecuritySchemeOAuth2 (mempty & implicit ?~ OAuth2Flow
             { _oAuth2Params = OAuth2ImplicitFlow "http://swagger.io/api/oauth/dialog"
             , _oAath2RefreshUrl = Nothing
             , _oAuth2Scopes =
                 [ ("write:pets",  "modify pets in your account")
-                , ("read:pets", "read your pets") ] } )
-      , _securitySchemeDescription = Nothing }) ]
+                , ("read:pets", "read your pets") ]
+            , _oAuth2Extensions = mempty  } )
+      , _securitySchemeDescription = Nothing
+      , _securitySchemeExtensions = SpecificationExtensions (InsOrdHM.fromList [("ext1", toJSON True)])})]
 
 securityDefinitionsExampleJSON :: Value
 securityDefinitionsExampleJSON = [aesonQQ|
@@ -484,7 +495,8 @@ securityDefinitionsExampleJSON = [aesonQQ|
         },
         "authorizationUrl": "http://swagger.io/api/oauth/dialog"
       }
-    }
+    },
+  "x-ext1": true
   }
 }
 
@@ -497,8 +509,10 @@ oAuth2SecurityDefinitionsReadExample = SecurityDefinitions
             { _oAuth2Params = OAuth2ImplicitFlow "http://swagger.io/api/oauth/dialog"
             , _oAath2RefreshUrl = Nothing
             , _oAuth2Scopes =
-              [ ("read:pets", "read your pets") ] } )
-      , _securitySchemeDescription = Nothing })
+              [ ("read:pets", "read your pets") ]
+            , _oAuth2Extensions = mempty } )
+      , _securitySchemeDescription = Nothing
+      , _securitySchemeExtensions = mempty })
   ]
 
 oAuth2SecurityDefinitionsWriteExample :: SecurityDefinitions
@@ -508,8 +522,10 @@ oAuth2SecurityDefinitionsWriteExample = SecurityDefinitions
             { _oAuth2Params = OAuth2ImplicitFlow "http://swagger.io/api/oauth/dialog"
             , _oAath2RefreshUrl = Nothing
             , _oAuth2Scopes =
-                [ ("write:pets", "modify pets in your account") ] } )
-      , _securitySchemeDescription = Nothing })
+                [ ("write:pets", "modify pets in your account") ]
+            , _oAuth2Extensions = mempty } )
+      , _securitySchemeDescription = Nothing
+      , _securitySchemeExtensions = mempty })
   ]
 
 oAuth2SecurityDefinitionsEmptyExample :: SecurityDefinitions
@@ -615,6 +631,7 @@ swaggerExample = mempty
       & license ?~ "MIT"
       & license._Just.url ?~ URL "http://mit.com"
       & description ?~ "This is an API that tests servant-swagger support for a Todo API")
+
   & paths.at "/todo/{id}" ?~ (mempty & get ?~ ((mempty :: Operation)
       & responses . at 200 ?~ Inline (mempty
           & description .~ "OK"