--- a/dom/media/webspeech/synth/SpeechSynthesisUtterance.cpp
+++ b/dom/media/webspeech/synth/SpeechSynthesisUtterance.cpp
@@ -143,16 +143,22 @@ SpeechSynthesisUtterance::Pitch() const
 
 void
 SpeechSynthesisUtterance::SetPitch(float aPitch)
 {
   mPitch = aPitch;
 }
 
 void
+SpeechSynthesisUtterance::GetChosenVoiceURI(nsString& aResult) const
+{
+  aResult = mChosenVoiceURI;
+}
+
+void
 SpeechSynthesisUtterance::DispatchSpeechSynthesisEvent(const nsAString& aEventType,
                                                        uint32_t aCharIndex,
                                                        float aElapsedTime,
                                                        const nsAString& aName)
 {
   SpeechSynthesisEventInit init;
   init.mBubbles = false;
   init.mCancelable = false;

--- a/dom/media/webspeech/synth/SpeechSynthesisUtterance.h
+++ b/dom/media/webspeech/synth/SpeechSynthesisUtterance.h
@@ -66,16 +66,18 @@ public:
   float Rate() const;
 
   void SetRate(float aRate);
 
   float Pitch() const;
 
   void SetPitch(float aPitch);
 
+  void GetChosenVoiceURI(nsString& aResult) const;
+
   enum {
     STATE_NONE,
     STATE_PENDING,
     STATE_SPEAKING,
     STATE_ENDED
   };
 
   uint32_t GetState() { return mState; }
@@ -102,16 +104,18 @@ private:
   nsString mLang;
 
   float mVolume;
 
   float mRate;
 
   float mPitch;
 
+  nsString mChosenVoiceURI;
+
   uint32_t mState;
 
   bool mPaused;
 
   nsRefPtr<SpeechSynthesisVoice> mVoice;
 };
 
 } // namespace dom

--- a/dom/media/webspeech/synth/ipc/PSpeechSynthesisRequest.ipdl
+++ b/dom/media/webspeech/synth/ipc/PSpeechSynthesisRequest.ipdl
@@ -20,17 +20,17 @@ async protocol PSpeechSynthesisRequest
   Resume();
 
   Cancel();
 
  child:
 
   __delete__(bool aIsError, float aElapsedTime, uint32_t aCharIndex);
 
-  OnStart();
+  OnStart(nsString aUri);
 
   OnPause(float aElapsedTime, uint32_t aCharIndex);
 
   OnResume(float aElapsedTime, uint32_t aCharIndex);
 
   OnBoundary(nsString aName, float aElapsedTime, uint32_t aCharIndex);
 
   OnMark(nsString aName, float aElapsedTime, uint32_t aCharIndex);

--- a/dom/media/webspeech/synth/ipc/SpeechSynthesisChild.cpp
+++ b/dom/media/webspeech/synth/ipc/SpeechSynthesisChild.cpp
@@ -68,19 +68,19 @@ SpeechSynthesisRequestChild::SpeechSynth
 }
 
 SpeechSynthesisRequestChild::~SpeechSynthesisRequestChild()
 {
   MOZ_COUNT_DTOR(SpeechSynthesisRequestChild);
 }
 
 bool
-SpeechSynthesisRequestChild::RecvOnStart()
+SpeechSynthesisRequestChild::RecvOnStart(const nsString& aUri)
 {
-  mTask->DispatchStartImpl();
+  mTask->DispatchStartImpl(aUri);
   return true;
 }
 
 bool
 SpeechSynthesisRequestChild::Recv__delete__(const bool& aIsError,
                                             const float& aElapsedTime,
                                             const uint32_t& aCharIndex)
 {

--- a/dom/media/webspeech/synth/ipc/SpeechSynthesisChild.h
+++ b/dom/media/webspeech/synth/ipc/SpeechSynthesisChild.h
@@ -43,17 +43,17 @@ protected:
 
 class SpeechSynthesisRequestChild : public PSpeechSynthesisRequestChild
 {
 public:
   explicit SpeechSynthesisRequestChild(SpeechTaskChild* aTask);
   virtual ~SpeechSynthesisRequestChild();
 
 protected:
-  virtual bool RecvOnStart() override;
+  virtual bool RecvOnStart(const nsString& aUri) override;
 
   virtual bool Recv__delete__(const bool& aIsError,
                               const float& aElapsedTime,
                               const uint32_t& aCharIndex) override;
 
   virtual bool RecvOnPause(const float& aElapsedTime, const uint32_t& aCharIndex) override;
 
   virtual bool RecvOnResume(const float& aElapsedTime, const uint32_t& aCharIndex) override;

--- a/dom/media/webspeech/synth/ipc/SpeechSynthesisParent.cpp
+++ b/dom/media/webspeech/synth/ipc/SpeechSynthesisParent.cpp
@@ -115,20 +115,20 @@ SpeechSynthesisRequestParent::RecvCancel
   MOZ_ASSERT(mTask);
   mTask->Cancel();
   return true;
 }
 
 // SpeechTaskParent
 
 nsresult
-SpeechTaskParent::DispatchStartImpl()
+SpeechTaskParent::DispatchStartImpl(const nsAString& aUri)
 {
   MOZ_ASSERT(mActor);
-  NS_ENSURE_TRUE(mActor->SendOnStart(), NS_ERROR_FAILURE);
+  NS_ENSURE_TRUE(mActor->SendOnStart(nsString(aUri)), NS_ERROR_FAILURE);
 
   return NS_OK;
 }
 
 nsresult
 SpeechTaskParent::DispatchEndImpl(float aElapsedTime, uint32_t aCharIndex)
 {
   MOZ_ASSERT(mActor);

--- a/dom/media/webspeech/synth/ipc/SpeechSynthesisParent.h
+++ b/dom/media/webspeech/synth/ipc/SpeechSynthesisParent.h
@@ -70,17 +70,17 @@ protected:
 
 class SpeechTaskParent : public nsSpeechTask
 {
   friend class SpeechSynthesisRequestParent;
 public:
   SpeechTaskParent(float aVolume, const nsAString& aUtterance)
     : nsSpeechTask(aVolume, aUtterance) {}
 
-  virtual nsresult DispatchStartImpl();
+  virtual nsresult DispatchStartImpl(const nsAString& aUri);
 
   virtual nsresult DispatchEndImpl(float aElapsedTime, uint32_t aCharIndex);
 
   virtual nsresult DispatchPauseImpl(float aElapsedTime, uint32_t aCharIndex);
 
   virtual nsresult DispatchResumeImpl(float aElapsedTime, uint32_t aCharIndex);
 
   virtual nsresult DispatchErrorImpl(float aElapsedTime, uint32_t aCharIndex);

--- a/dom/media/webspeech/synth/nsSpeechTask.cpp
+++ b/dom/media/webspeech/synth/nsSpeechTask.cpp
@@ -135,16 +135,22 @@ nsSpeechTask::~nsSpeechTask()
 
 void
 nsSpeechTask::BindStream(ProcessedMediaStream* aStream)
 {
   mStream = MediaStreamGraph::GetInstance()->CreateSourceStream(nullptr);
   mPort = aStream->AllocateInputPort(mStream, 0);
 }
 
+void
+nsSpeechTask::SetChosenVoiceURI(const nsAString& aUri)
+{
+  mChosenVoiceURI = aUri;
+}
+
 NS_IMETHODIMP
 nsSpeechTask::Setup(nsISpeechTaskCallback* aCallback,
                     uint32_t aChannels, uint32_t aRate, uint8_t argc)
 {
   MOZ_ASSERT(XRE_GetProcessType() == GeckoProcessType_Default);
 
   LOG(PR_LOG_DEBUG, ("nsSpeechTask::Setup"));
 
@@ -277,23 +283,30 @@ nsSpeechTask::DispatchStart()
   }
 
   return DispatchStartImpl();
 }
 
 nsresult
 nsSpeechTask::DispatchStartImpl()
 {
+  return DispatchStartImpl(mChosenVoiceURI);
+}
+
+nsresult
+nsSpeechTask::DispatchStartImpl(const nsAString& aUri)
+{
   LOG(PR_LOG_DEBUG, ("nsSpeechTask::DispatchStart"));
 
   MOZ_ASSERT(mUtterance);
   NS_ENSURE_TRUE(mUtterance->mState == SpeechSynthesisUtterance::STATE_PENDING,
                  NS_ERROR_NOT_AVAILABLE);
 
   mUtterance->mState = SpeechSynthesisUtterance::STATE_SPEAKING;
+  mUtterance->mChosenVoiceURI = aUri;
   mUtterance->DispatchSpeechSynthesisEvent(NS_LITERAL_STRING("start"), 0, 0,
                                            NS_LITERAL_STRING(""));
 
   return NS_OK;
 }
 
 NS_IMETHODIMP
 nsSpeechTask::DispatchEnd(float aElapsedTime, uint32_t aCharIndex)

--- a/dom/media/webspeech/synth/nsSpeechTask.h
+++ b/dom/media/webspeech/synth/nsSpeechTask.h
@@ -42,20 +42,24 @@ public:
   uint32_t GetCurrentCharOffset();
 
   void SetSpeechSynthesis(SpeechSynthesis* aSpeechSynthesis);
 
   void SetIndirectAudio(bool aIndirectAudio) { mIndirectAudio = aIndirectAudio; }
 
   void BindStream(ProcessedMediaStream* aStream);
 
+  void SetChosenVoiceURI(const nsAString& aUri);
+
 protected:
   virtual ~nsSpeechTask();
 
-  virtual nsresult DispatchStartImpl();
+  nsresult DispatchStartImpl();
+
+  virtual nsresult DispatchStartImpl(const nsAString& aUri);
 
   virtual nsresult DispatchEndImpl(float aElapsedTime, uint32_t aCharIndex);
 
   virtual nsresult DispatchPauseImpl(float aElapsedTime, uint32_t aCharIndex);
 
   virtual nsresult DispatchResumeImpl(float aElapsedTime, uint32_t aCharIndex);
 
   virtual nsresult DispatchErrorImpl(float aElapsedTime, uint32_t aCharIndex);
@@ -84,14 +88,16 @@ private:
 
   nsCOMPtr<nsISpeechTaskCallback> mCallback;
 
   uint32_t mChannels;
 
   nsRefPtr<SpeechSynthesis> mSpeechSynthesis;
 
   bool mIndirectAudio;
+
+  nsString mChosenVoiceURI;
 };
 
 } // namespace dom
 } // namespace mozilla
 
 #endif

--- a/dom/media/webspeech/synth/nsSynthVoiceRegistry.cpp
+++ b/dom/media/webspeech/synth/nsSynthVoiceRegistry.cpp
@@ -562,16 +562,18 @@ nsSynthVoiceRegistry::Speak(const nsAStr
   VoiceData* voice = FindBestMatch(aUri, aLang);
 
   if (!voice) {
     NS_WARNING("No voices found.");
     aTask->DispatchError(0, 0);
     return;
   }
 
+  aTask->SetChosenVoiceURI(voice->mUri);
+
   LOG(PR_LOG_DEBUG, ("nsSynthVoiceRegistry::Speak - Using voice URI: %s",
                      NS_ConvertUTF16toUTF8(voice->mUri).get()));
 
   SpeechServiceType serviceType;
 
   DebugOnly<nsresult> rv = voice->mService->GetServiceType(&serviceType);
   NS_WARN_IF_FALSE(NS_SUCCEEDED(rv), "Failed to get speech service type");
 

--- a/dom/webidl/SpeechSynthesisUtterance.webidl
+++ b/dom/webidl/SpeechSynthesisUtterance.webidl
@@ -23,9 +23,12 @@ interface SpeechSynthesisUtterance : Eve
 
   attribute EventHandler onstart;
   attribute EventHandler onend;
   attribute EventHandler onerror;
   attribute EventHandler onpause;
   attribute EventHandler onresume;
   attribute EventHandler onmark;
   attribute EventHandler onboundary;
+
+  [ChromeOnly]
+  readonly attribute DOMString chosenVoiceURI;
 };