diff --git a/constants.h b/constants.h
index dc39d5a..c6ffb74 100644
--- a/constants.h
+++ b/constants.h
@@ -71,6 +71,19 @@
   kNumDownloadSources
 } DownloadSource;
 
+// A payload can be a Full or Delta payload. In some cases, a Full payload is
+// used even when a Delta payload was available for the update, called here
+// ForcedFull. The PayloadType enum is only used to send UMA metrics about the
+// successfully applied payload.
+typedef enum {
+  kPayloadTypeFull,
+  kPayloadTypeDelta,
+  kPayloadTypeForcedFull,
+
+  // Note: Add new payload types only above this line.
+  kNumPayloadTypes
+} PayloadType;
+
 // The default number of UMA buckets for metrics.
 const int kNumDefaultUmaBuckets = 50;
 
diff --git a/payload_state.cc b/payload_state.cc
index 20e2cac..a933ea5 100644
--- a/payload_state.cc
+++ b/payload_state.cc
@@ -156,6 +156,7 @@
   ReportRebootMetrics();
   ReportDurationMetrics();
   ReportUpdatesAbandonedCountMetric();
+  ReportPayloadTypeMetric();
 
   // Reset the number of responses seen since it counts from the last
   // successful update, e.g. now.
@@ -877,6 +878,28 @@
   prefs_->Delete(kPrefsUpdateDurationUptime);
 }
 
+void PayloadState::ReportPayloadTypeMetric() {
+  string metric;
+  PayloadType uma_payload_type;
+  OmahaRequestParams* params = system_state_->request_params();
+
+  if (response_.is_delta_payload) {
+    uma_payload_type = kPayloadTypeDelta;
+  } else if (params->delta_okay()) {
+    uma_payload_type = kPayloadTypeFull;
+  } else { // Full payload, delta was not allowed by request.
+    uma_payload_type = kPayloadTypeForcedFull;
+  }
+
+  metric = "Installer.PayloadFormat";
+  system_state_->metrics_lib()->SendEnumToUMA(
+      metric,
+      uma_payload_type,
+      kNumPayloadTypes);
+  LOG(INFO) << "Uploading " << utils::ToString(uma_payload_type)
+            << " for metric " <<  metric;
+}
+
 string PayloadState::GetPrefsKey(const string& prefix, DownloadSource source) {
   return prefix + "-from-" + utils::ToString(source);
 }
diff --git a/payload_state.h b/payload_state.h
index 3c88622..c4651e9 100644
--- a/payload_state.h
+++ b/payload_state.h
@@ -134,6 +134,9 @@
   // Reports the various metrics related to update duration.
   void ReportDurationMetrics();
 
+  // Reports the metric related to the applied payload type.
+  void ReportPayloadTypeMetric();
+
   // Resets all the persisted state values which are maintained relative to the
   // current response signature. The response signature itself is not reset.
   void ResetPersistedState();
diff --git a/payload_state_unittest.cc b/payload_state_unittest.cc
index dcdcd11..9bd4c08 100644
--- a/payload_state_unittest.cc
+++ b/payload_state_unittest.cc
@@ -714,6 +714,8 @@
       "Installer.DownloadSourcesUsed", 3, _, _, _));
   EXPECT_CALL(*mock_system_state.mock_metrics_lib(), SendToUMA(
       "Installer.DownloadOverheadPercentage", 542, _, _, _));
+  EXPECT_CALL(*mock_system_state.mock_metrics_lib(), SendEnumToUMA(
+      "Installer.PayloadFormat", kPayloadTypeFull, kNumPayloadTypes));
 
   payload_state.UpdateSucceeded();
 
@@ -989,4 +991,80 @@
   EXPECT_EQ(0, payload_state.GetUrlFailureCount());
 }
 
+TEST(PayloadStateTest, PayloadTypeMetricWhenTypeIsDelta) {
+  OmahaResponse response;
+  response.is_delta_payload = true;
+  PayloadState payload_state;
+  MockSystemState mock_system_state;
+
+  EXPECT_TRUE(payload_state.Initialize(&mock_system_state));
+  SetupPayloadStateWith2Urls("Hash6437", true, &payload_state, &response);
+
+  // Simulate a successful download and update.
+  payload_state.DownloadComplete();
+
+  EXPECT_CALL(*mock_system_state.mock_metrics_lib(), SendEnumToUMA(
+      "Installer.PayloadFormat", kPayloadTypeDelta, kNumPayloadTypes));
+  payload_state.UpdateSucceeded();
+
+  // Mock the request to a request where the delta was disabled but Omaha sends
+  // a delta anyway and test again.
+  OmahaRequestParams params(&mock_system_state);
+  params.set_delta_okay(false);
+  mock_system_state.set_request_params(&params);
+
+  EXPECT_TRUE(payload_state.Initialize(&mock_system_state));
+  SetupPayloadStateWith2Urls("Hash6437", true, &payload_state, &response);
+
+  payload_state.DownloadComplete();
+
+  EXPECT_CALL(*mock_system_state.mock_metrics_lib(), SendEnumToUMA(
+      "Installer.PayloadFormat", kPayloadTypeDelta, kNumPayloadTypes));
+  payload_state.UpdateSucceeded();
+}
+
+TEST(PayloadStateTest, PayloadTypeMetricWhenTypeIsForcedFull) {
+  OmahaResponse response;
+  response.is_delta_payload = false;
+  PayloadState payload_state;
+  MockSystemState mock_system_state;
+
+  EXPECT_TRUE(payload_state.Initialize(&mock_system_state));
+  SetupPayloadStateWith2Urls("Hash6437", true, &payload_state, &response);
+
+  // Mock the request to a request where the delta was disabled.
+  OmahaRequestParams params(&mock_system_state);
+  params.set_delta_okay(false);
+  mock_system_state.set_request_params(&params);
+
+  // Simulate a successful download and update.
+  payload_state.DownloadComplete();
+
+  EXPECT_CALL(*mock_system_state.mock_metrics_lib(), SendEnumToUMA(
+      "Installer.PayloadFormat", kPayloadTypeForcedFull, kNumPayloadTypes));
+  payload_state.UpdateSucceeded();
+}
+
+TEST(PayloadStateTest, PayloadTypeMetricWhenTypeIsFull) {
+  OmahaResponse response;
+  response.is_delta_payload = false;
+  PayloadState payload_state;
+  MockSystemState mock_system_state;
+
+  EXPECT_TRUE(payload_state.Initialize(&mock_system_state));
+  SetupPayloadStateWith2Urls("Hash6437", true, &payload_state, &response);
+
+  // Mock the request to a request where the delta was disabled.
+  OmahaRequestParams params(&mock_system_state);
+  params.set_delta_okay(true);
+  mock_system_state.set_request_params(&params);
+
+  // Simulate a successful download and update.
+  payload_state.DownloadComplete();
+
+  EXPECT_CALL(*mock_system_state.mock_metrics_lib(), SendEnumToUMA(
+      "Installer.PayloadFormat", kPayloadTypeFull, kNumPayloadTypes));
+  payload_state.UpdateSucceeded();
+}
+
 }
diff --git a/utils.cc b/utils.cc
index 62581f4..2bcc311 100644
--- a/utils.cc
+++ b/utils.cc
@@ -802,7 +802,7 @@
   return (b ? "true" : "false");
 }
 
-std::string ToString(DownloadSource source) {
+string ToString(DownloadSource source) {
   switch (source) {
     case kDownloadSourceHttpsServer: return "HttpsServer";
     case kDownloadSourceHttpServer:  return "HttpServer";
@@ -814,6 +814,19 @@
   return "Unknown";
 }
 
+string ToString(PayloadType payload_type) {
+  switch (payload_type) {
+    case kPayloadTypeDelta:      return "Delta";
+    case kPayloadTypeFull:       return "Full";
+    case kPayloadTypeForcedFull: return "ForcedFull";
+    case kNumPayloadTypes:       return "Unknown";
+    // Don't add a default case to let the compiler warn about newly added
+    // payload types which should be added here.
+  }
+
+  return "Unknown";
+}
+
 ErrorCode GetBaseErrorCode(ErrorCode code) {
   // Ignore the higher order bits in the code by applying the mask as
   // we want the enumerations to be in the small contiguous range
diff --git a/utils.h b/utils.h
index 0fe2948..bd4d2d6 100644
--- a/utils.h
+++ b/utils.h
@@ -168,6 +168,9 @@
 // Returns a string representation of the given enum.
 std::string ToString(DownloadSource source);
 
+// Returns a string representation of the given enum.
+std::string ToString(PayloadType payload_type);
+
 enum BootLoader {
   BootLoader_SYSLINUX = 0,
   BootLoader_CHROME_FIRMWARE = 1