diff --git a/model/fn-execution/src/main/proto/org/apache/beam/model/fn_execution/v1/beam_fn_api.proto b/model/fn-execution/src/main/proto/org/apache/beam/model/fn_execution/v1/beam_fn_api.proto
index 42c2d7778a0c..9360522ab409 100644
--- a/model/fn-execution/src/main/proto/org/apache/beam/model/fn_execution/v1/beam_fn_api.proto
+++ b/model/fn-execution/src/main/proto/org/apache/beam/model/fn_execution/v1/beam_fn_api.proto
@@ -740,6 +740,12 @@ message Elements {
     bool is_last = 4;
   }
 
+  // Element metadata passed as part of WindowedValue to make WindowedValue
+  // extensible and backward compatible
+  message ElementMetadata {
+    // empty message - add drain, kind, tracing metadata in the future
+  }
+
   // Represent the encoded user timer for a given instruction, transform and
   // timer id.
   message Timers {
diff --git a/model/pipeline/src/main/proto/org/apache/beam/model/pipeline/v1/beam_runner_api.proto b/model/pipeline/src/main/proto/org/apache/beam/model/pipeline/v1/beam_runner_api.proto
index e600e34657e7..c615b2a5279a 100644
--- a/model/pipeline/src/main/proto/org/apache/beam/model/pipeline/v1/beam_runner_api.proto
+++ b/model/pipeline/src/main/proto/org/apache/beam/model/pipeline/v1/beam_runner_api.proto
@@ -1677,6 +1677,10 @@ message StandardProtocols {
     // Indicates whether the SDK supports ordered list state.
     ORDERED_LIST_STATE = 10
     [(beam_urn) = "beam:protocol:ordered_list_state:v1"];
+
+    // Indicates support for reading, writing and propagating Element's metadata
+    ELEMENT_METADATA = 11
+    [(beam_urn) = "beam:protocol:element_metadata:v1"];
   }
 }