--- a/dom/media/eme/MediaKeys.cpp
+++ b/dom/media/eme/MediaKeys.cpp
@@ -8,16 +8,17 @@
 #include "GMPService.h"
 #include "mozilla/dom/HTMLMediaElement.h"
 #include "mozilla/dom/MediaKeysBinding.h"
 #include "mozilla/dom/MediaKeyMessageEvent.h"
 #include "mozilla/dom/MediaKeyError.h"
 #include "mozilla/dom/MediaKeySession.h"
 #include "mozilla/dom/DOMException.h"
 #include "mozilla/dom/UnionTypes.h"
+#include "mozilla/Telemetry.h"
 #include "GMPCDMProxy.h"
 #include "mozilla/EMEUtils.h"
 #include "nsContentUtils.h"
 #include "nsIScriptObjectPrincipal.h"
 #include "nsContentTypeParser.h"
 #ifdef MOZ_FMP4
 #include "MP4Decoder.h"
 #endif
@@ -395,16 +396,36 @@ MediaKeys::Init(ErrorResult& aRv)
                NS_ConvertUTF8toUTF16(origin),
                NS_ConvertUTF8toUTF16(topLevelOrigin),
                KeySystemToGMPName(mKeySystem),
                inPrivateBrowsing);
 
   return promise.forget();
 }
 
+enum CDMCreatedType {
+  eClearKey = 0,
+  ePrimetime = 1,
+  eWidevine = 2,
+  eUnknown = 3
+};
+
+static CDMCreatedType
+ToCDMCreatedTelemetryEnum(const nsString& aKeySystem)
+{
+  if (!CompareUTF8toUTF16(kEMEKeySystemWidevine, aKeySystem)) {
+    return CDMCreatedType::eWidevine;
+  } else if (!CompareUTF8toUTF16(kEMEKeySystemClearkey, aKeySystem)) {
+    return CDMCreatedType::eClearKey;
+  } else if (!CompareUTF8toUTF16(kEMEKeySystemPrimetime, aKeySystem)) {
+    return CDMCreatedType::ePrimetime;
+  }
+  return CDMCreatedType::eUnknown;
+}
+
 void
 MediaKeys::OnCDMCreated(PromiseId aId, const nsACString& aNodeId, const uint32_t aPluginId)
 {
   RefPtr<DetailedPromise> promise(RetrievePromise(aId));
   if (!promise) {
     return;
   }
   mNodeId = aNodeId;
@@ -413,16 +434,18 @@ MediaKeys::OnCDMCreated(PromiseId aId, c
   promise->MaybeResolve(keys);
   if (mCreatePromiseId == aId) {
     Release();
   }
 
   MediaKeySystemAccess::NotifyObservers(mParent,
                                         mKeySystem,
                                         MediaKeySystemStatus::Cdm_created);
+
+  Telemetry::Accumulate(Telemetry::VIDEO_CDM_CREATED, ToCDMCreatedTelemetryEnum(mKeySystem));
 }
 
 already_AddRefed<MediaKeySession>
 MediaKeys::CreateSession(JSContext* aCx,
                          MediaKeySessionType aSessionType,
                          ErrorResult& aRv)
 {
   if (!mProxy) {

--- a/toolkit/components/telemetry/Histograms.json
+++ b/toolkit/components/telemetry/Histograms.json
@@ -8580,16 +8580,25 @@
     "expires_in_version": "55",
     "bug_numbers": [1230265],
     "kind": "linear",
     "high": 1000,
     "n_buckets": 100,
     "description": "720p VP9 decode benchmark measurement in frames per second",
     "releaseChannelCollection": "opt-out"
   },
+  "VIDEO_CDM_CREATED": {
+    "alert_emails": ["cpearce@mozilla.com"],
+    "expires_in_version": "58",
+    "bug_numbers": [1304207],
+    "kind": "enumerated",
+    "n_values": 6,
+    "description": "Note the type of CDM (0=ClearKey, 1=Primetime, 2=Widevine, 3=unknown) every time we successfully instantiate an EME MediaKeys object.",
+    "releaseChannelCollection": "opt-out"
+  },
   "MEDIA_CODEC_USED": {
     "alert_emails": ["cpearce@mozilla.com"],
     "expires_in_version": "never",
     "keyed": true,
     "kind": "count",
     "description": "Count of use of audio/video codecs in HTMLMediaElements and WebAudio. Those with 'resource' prefix are approximate; report based on HTTP ContentType or sniffing. Those with 'webaudio' prefix are for WebAudio."
   },
   "FX_SANITIZE_TOTAL": {