diff --git a/ddtrace/tracer/transport.go b/ddtrace/tracer/transport.go
index 222f6c8b70..1cf84254ad 100644
--- a/ddtrace/tracer/transport.go
+++ b/ddtrace/tracer/transport.go
@@ -104,6 +104,9 @@ func newHTTPTransport(url string, client *http.Client) *httpTransport {
 	if eid := internal.EntityID(); eid != "" {
 		defaultHeaders["Datadog-Entity-ID"] = eid
 	}
+	if extEnv := internal.ExternalEnvironment(); extEnv != "" {
+		defaultHeaders["Datadog-External-Env"] = extEnv
+	}
 	return &httpTransport{
 		traceURL: fmt.Sprintf("%s/v0.4/traces", url),
 		statsURL: fmt.Sprintf("%s/v0.6/stats", url),
diff --git a/ddtrace/tracer/transport_test.go b/ddtrace/tracer/transport_test.go
index b8967713cf..efcafde18f 100644
--- a/ddtrace/tracer/transport_test.go
+++ b/ddtrace/tracer/transport_test.go
@@ -396,3 +396,30 @@ func TestWithUDS(t *testing.T) {
 	assert.Len(rt.reqs, 1)
 	assert.Equal(hits, 2)
 }
+
+func TestExternalEnvironment(t *testing.T) {
+	t.Setenv("DD_EXTERNAL_ENV", "it-false,cn-nginx-webserver,pu-75a2b6d5-3949-4afb-ad0d-92ff0674e759")
+	assert := assert.New(t)
+	found := false
+	srv := httptest.NewServer(http.HandlerFunc(func(_ http.ResponseWriter, r *http.Request) {
+		extEnv := r.Header.Get("Datadog-External-Env")
+		if extEnv == "" {
+			return
+		}
+		assert.Equal("it-false,cn-nginx-webserver,pu-75a2b6d5-3949-4afb-ad0d-92ff0674e759", extEnv)
+		found = true
+	}))
+	defer srv.Close()
+
+	u, err := url.Parse(srv.URL)
+	assert.NoError(err)
+	c := &http.Client{}
+	trc := newTracer(WithAgentTimeout(2), WithAgentAddr(u.Host), WithHTTPClient(c))
+	defer trc.Stop()
+
+	p, err := encode(getTestTrace(1, 1))
+	assert.NoError(err)
+	_, err = trc.config.transport.send(p)
+	assert.NoError(err)
+	assert.True(found)
+}
diff --git a/internal/container_linux.go b/internal/container_linux.go
index 237c293e21..6ac57029f9 100644
--- a/internal/container_linux.go
+++ b/internal/container_linux.go
@@ -48,7 +48,7 @@ var (
 	// containerID is the containerID read at init from /proc/self/cgroup
 	containerID string
 
-	// entityID is the entityID to use for the container. It is the `cid-<containerID>` if the container id available,
+	// entityID is the entityID to use for the container. It is the `ci-<containerID>` if the container id available,
 	// otherwise the cgroup node controller's inode prefixed with `in-` or an empty string on incompatible OS.
 	// We use the memory controller on cgroupv1 and the root cgroup on cgroupv2.
 	entityID string
@@ -151,7 +151,7 @@ func readEntityID(mountPath, cgroupPath string, isHostCgroupNamespace bool) stri
 	// First try to emit the containerID if available. It will be retrieved if the container is
 	// running in the host cgroup namespace, independently of the cgroup version.
 	if containerID != "" {
-		return "cid-" + containerID
+		return "ci-" + containerID
 	}
 	// Rely on the inode if we're not running in the host cgroup namespace.
 	if isHostCgroupNamespace {
@@ -161,7 +161,7 @@ func readEntityID(mountPath, cgroupPath string, isHostCgroupNamespace bool) stri
 }
 
 // EntityID attempts to return the container ID or the cgroup node controller's inode if the container ID
-// is not available. The cid is prefixed with `cid-` and the inode with `in-`.
+// is not available. The cid is prefixed with `ci-` and the inode with `in-`.
 func EntityID() string {
 	return entityID
 }
diff --git a/internal/container_linux_test.go b/internal/container_linux_test.go
index 029ff647c4..83796086f7 100644
--- a/internal/container_linux_test.go
+++ b/internal/container_linux_test.go
@@ -93,7 +93,7 @@ func TestReadEntityIDPrioritizeCID(t *testing.T) {
 
 	containerID = "fakeContainerID"
 	eid := readEntityID("", "", true)
-	assert.Equal(t, "cid-fakeContainerID", eid)
+	assert.Equal(t, "ci-fakeContainerID", eid)
 }
 
 func TestReadEntityIDFallbackOnInode(t *testing.T) {
diff --git a/internal/container_stub.go b/internal/container_stub.go
index c6c2487406..38f4e5ce21 100644
--- a/internal/container_stub.go
+++ b/internal/container_stub.go
@@ -13,7 +13,7 @@ func ContainerID() string {
 }
 
 // EntityID attempts to return the container ID or the cgroup v2 node inode if the container ID is not available.
-// The cid is prefixed with `cid-` and the inode with `in-`.
+// The cid is prefixed with `ci-` and the inode with `in-`.
 func EntityID() string {
 	return ""
 }
diff --git a/internal/env.go b/internal/env.go
index 2e760526ac..ace2bba238 100644
--- a/internal/env.go
+++ b/internal/env.go
@@ -133,3 +133,8 @@ func BoolVal(val string, def bool) bool {
 	}
 	return v
 }
+
+// ExternalEnvironment returns the value of the DD_EXTERNAL_ENV environment variable.
+func ExternalEnvironment() string {
+	return os.Getenv("DD_EXTERNAL_ENV")
+}
diff --git a/internal/telemetry/client_test.go b/internal/telemetry/client_test.go
index 033b2e277a..45cd4172a3 100644
--- a/internal/telemetry/client_test.go
+++ b/internal/telemetry/client_test.go
@@ -11,6 +11,7 @@ import (
 	"net/http"
 	"net/http/httptest"
 	"reflect"
+	"runtime"
 	"sort"
 	"sync"
 	"testing"
@@ -18,6 +19,7 @@ import (
 
 	"github.com/stretchr/testify/assert"
 
+	"gopkg.in/DataDog/dd-trace-go.v1/internal"
 	logging "gopkg.in/DataDog/dd-trace-go.v1/internal/log"
 )
 
@@ -439,11 +441,18 @@ func Test_heartbeatInterval(t *testing.T) {
 }
 
 func TestNoEmptyHeaders(t *testing.T) {
+	if runtime.GOOS != "linux" {
+		t.Skip("skipping test on non-linux OS")
+	}
+	if internal.EntityID() == "" || internal.ContainerID() == "" {
+		t.Skip("skipping test when entity ID and container ID are not available")
+	}
 	c := &client{}
 	req := c.newRequest(RequestTypeAppStarted)
 	assertNotEmpty := func(header string) {
 		headers := *req.Header
 		vals := headers[header]
+		assert.Greater(t, len(vals), 0, "header %s should not be empty", header)
 		for _, v := range vals {
 			assert.NotEmpty(t, v, "%s header should not be empty", header)
 		}