diff --git a/extensions.go b/extensions.go
new file mode 100644
index 00000000..5023fa04
--- /dev/null
+++ b/extensions.go
@@ -0,0 +1,21 @@
+package restful
+
+// Copyright 2021 Ernest Micklei. All rights reserved.
+// Use of this source code is governed by a license
+// that can be found in the LICENSE file.
+
+// ExtensionProperties provides storage of vendor extensions for entities
+type ExtensionProperties struct {
+	// Extensions vendor extensions used to describe extra functionality
+	// (https://swagger.io/docs/specification/2-0/swagger-extensions/)
+	Extensions map[string]interface{}
+}
+
+// AddExtension adds or updates a key=value pair to the extension map.
+func (ep *ExtensionProperties) AddExtension(key string, value interface{}) {
+	if ep.Extensions == nil {
+		ep.Extensions = map[string]interface{}{key: value}
+	} else {
+		ep.Extensions[key] = value
+	}
+}
diff --git a/parameter.go b/parameter.go
index e8793304..c5555a86 100644
--- a/parameter.go
+++ b/parameter.go
@@ -52,6 +52,7 @@ type Parameter struct {
 // ParameterData represents the state of a Parameter.
 // It is made public to make it accessible to e.g. the Swagger package.
 type ParameterData struct {
+	ExtensionProperties
 	Name, Description, DataType, DataFormat string
 	Kind                                    int
 	Required                                bool
diff --git a/route.go b/route.go
index 6ac26129..f5661c90 100644
--- a/route.go
+++ b/route.go
@@ -19,6 +19,7 @@ type RouteSelectionConditionFunction func(httpRequest *http.Request) bool
 
 // Route binds a HTTP Method,Path,Consumes combination to a RouteFunction.
 type Route struct {
+	ExtensionProperties
 	Method   string
 	Produces []string
 	Consumes []string
diff --git a/route_builder.go b/route_builder.go
index d22fe1fb..23641b6d 100644
--- a/route_builder.go
+++ b/route_builder.go
@@ -38,6 +38,7 @@ type RouteBuilder struct {
 	errorMap                map[int]ResponseError
 	defaultResponse         *ResponseError
 	metadata                map[string]interface{}
+	extensions              map[string]interface{}
 	deprecated              bool
 	contentEncodingEnabled  *bool
 }
@@ -204,13 +205,22 @@ func (b *RouteBuilder) Metadata(key string, value interface{}) *RouteBuilder {
 	return b
 }
 
+// AddExtension adds or updates a key=value pair to the extensions map.
+func (b *RouteBuilder) AddExtension(key string, value interface{}) *RouteBuilder {
+	if b.extensions == nil {
+		b.extensions = map[string]interface{}{}
+	}
+	b.extensions[key] = value
+	return b
+}
+
 // Deprecate sets the value of deprecated to true.  Deprecated routes have a special UI treatment to warn against use
 func (b *RouteBuilder) Deprecate() *RouteBuilder {
 	b.deprecated = true
 	return b
 }
 
-// AllowedMethodsWithoutContentType overides the default list GET,HEAD,OPTIONS,DELETE,TRACE
+// AllowedMethodsWithoutContentType overrides the default list GET,HEAD,OPTIONS,DELETE,TRACE
 // If a request does not include a content-type header then
 // depending on the method, it may return a 415 Unsupported Media.
 // Must have uppercase HTTP Method names such as GET,HEAD,OPTIONS,...
@@ -221,6 +231,7 @@ func (b *RouteBuilder) AllowedMethodsWithoutContentType(methods []string) *Route
 
 // ResponseError represents a response; not necessarily an error.
 type ResponseError struct {
+	ExtensionProperties
 	Code      int
 	Message   string
 	Model     interface{}
@@ -335,6 +346,7 @@ func (b *RouteBuilder) Build() Route {
 		contentEncodingEnabled:           b.contentEncodingEnabled,
 		allowedMethodsWithoutContentType: b.allowedMethodsWithoutContentType,
 	}
+	route.Extensions = b.extensions
 	route.postBuild()
 	return route
 }
diff --git a/route_builder_test.go b/route_builder_test.go
index 17258d6e..933a423a 100644
--- a/route_builder_test.go
+++ b/route_builder_test.go
@@ -42,7 +42,13 @@ func TestRouteBuilder(t *testing.T) {
 	json := "application/json"
 	b := new(RouteBuilder)
 	b.To(dummy)
-	b.Path("/routes").Method("HEAD").Consumes(json).Produces(json).Metadata("test", "test-value").DefaultReturns("default", time.Now())
+	b.Path("/routes").
+		Method("HEAD").
+		Consumes(json).
+		Produces(json).
+		Metadata("test", "test-value").
+		AddExtension("x-restful-test", "test-value").
+		DefaultReturns("default", time.Now())
 	r := b.Build()
 	if r.Path != "/routes" {
 		t.Error("path invalid")
@@ -59,6 +65,9 @@ func TestRouteBuilder(t *testing.T) {
 	if r.Metadata["test"] != "test-value" {
 		t.Errorf("Metadata not set")
 	}
+	if r.Extensions["x-restful-test"] != "test-value" {
+		t.Errorf("Extensions not set")
+	}
 	if r.DefaultResponse == nil {
 		t.Fatal("expected default response")
 	}
@@ -91,13 +100,13 @@ func TestContentEncodingEnabled(t *testing.T) {
 	r := b.Build()
 
 	got := r.contentEncodingEnabled
-	var want *bool //nil
+	var want *bool // nil
 
 	if got != want {
 		t.Errorf("got %v want %v (default nil)", got, want)
 	}
 
-	//true
+	// true
 	b = new(RouteBuilder)
 	b.function = dummy
 	b.ContentEncodingEnabled(true)
@@ -108,7 +117,7 @@ func TestContentEncodingEnabled(t *testing.T) {
 		t.Errorf("got %v want %v (explicit true)", *got, true)
 	}
 
-	//true
+	// true
 	b = new(RouteBuilder)
 	b.function = dummy
 	b.ContentEncodingEnabled(false)