diff --git a/client.go b/client.go
index 2500fca..f323e70 100644
--- a/client.go
+++ b/client.go
@@ -18,6 +18,7 @@ const (
 	deprecatedSuffix = "/features"
 	clientName       = "unleash-client-go"
 	clientVersion    = "4.1.1"
+	specVersion      = "4.3.1"
 )
 
 var defaultStrategies = []strategy.Strategy{
diff --git a/metrics.go b/metrics.go
index ebda680..5477130 100644
--- a/metrics.go
+++ b/metrics.go
@@ -37,6 +37,9 @@ type MetricsData struct {
 
 	// Optional field that describes the sdk version (name:version)
 	SDKVersion string `json:"sdkVersion"`
+
+	// Which version of the Unleash-Client-Spec is this SDK validated against
+	SpecVersion string `json:"specVersion"`
 }
 
 // ClientData represents the data sent to the unleash during registration.
@@ -65,6 +68,9 @@ type ClientData struct {
 	PlatformName string `json:"platformName"`
 
 	YggdrasilVersion *string `json:"yggdrasilVersion"`
+
+	// Which version of the Unleash-Client-Spec is this SDK validated against
+	SpecVersion string `json:"specVersion"`
 }
 
 type metric struct {
@@ -204,6 +210,7 @@ func (m *metrics) sendMetrics() {
 		PlatformName:     "go",
 		PlatformVersion:  runtime.Version(),
 		YggdrasilVersion: nil,
+		SpecVersion:      specVersion,
 	}
 
 	u, _ := m.options.url.Parse("./client/metrics")
@@ -335,5 +342,6 @@ func (m *metrics) getClientData() ClientData {
 		runtime.Version(),
 		"go",
 		nil,
+		specVersion,
 	}
 }
diff --git a/metrics_test.go b/metrics_test.go
index f6bb6b6..270d3b5 100644
--- a/metrics_test.go
+++ b/metrics_test.go
@@ -456,6 +456,7 @@ func TestMetrics_ClientDataIncludesNewMetadata(t *testing.T) {
 			PlatformVersion:  runtime.Version(),
 			PlatformName:     "go",
 			YggdrasilVersion: nil,
+			SpecVersion:      specVersion,
 		}).
 		Reply(200)
 	client, err := NewClient(