--- a/dom/base/nsDocument.cpp
+++ b/dom/base/nsDocument.cpp
@@ -1454,16 +1454,18 @@ nsIDocument::nsIDocument()
     mAllowDoubleTapZoom(false),
     mValidScaleFloat(false),
     mValidMaxScale(false),
     mScaleStrEmpty(false),
     mWidthStrEmpty(false),
     mParserAborted(false),
     mReportedUseCounters(false),
     mHasReportedShadowDOMUsage(false),
+    mDocTreeHadAudibleMedia(false),
+    mDocTreeHadPlayRevoked(false),
 #ifdef DEBUG
     mWillReparent(false),
 #endif
     mPendingFullscreenRequests(0),
     mXMLDeclarationBits(0),
     mOnloadBlockCount(0),
     mAsyncOnloadBlockCount(0),
     mCompatMode(eCompatibility_FullStandards),
@@ -1631,16 +1633,24 @@ nsDocument::~nsDocument()
       }
       if (mHasUnsafeEvalCSP) {
         Accumulate(Telemetry::CSP_UNSAFE_EVAL_DOCUMENTS_COUNT, 1);
       }
 
       if (MOZ_UNLIKELY(mMathMLEnabled)) {
         ScalarAdd(Telemetry::ScalarID::MATHML_DOC_COUNT, 1);
       }
+
+      ScalarAdd(Telemetry::ScalarID::MEDIA_PAGE_COUNT, 1);
+      if (mDocTreeHadAudibleMedia) {
+        ScalarAdd(Telemetry::ScalarID::MEDIA_PAGE_HAD_MEDIA_COUNT, 1);
+      }
+      if (mDocTreeHadPlayRevoked) {
+        ScalarAdd(Telemetry::ScalarID::MEDIA_PAGE_HAD_PLAY_REVOKED_COUNT, 1);
+      }
     }
   }
 
   ReportUseCounters();
 
   mInDestructor = true;
   mInUnlinkOrDeletion = true;
 
@@ -12485,16 +12495,34 @@ nsIDocument::NotifyUserGestureActivation
             LogLevel::Debug,
             ("Document %p has been activated by user.", this));
     doc->mUserGestureActivated = true;
     doc = doc->GetSameTypeParentDocument();
   }
 }
 
 void
+nsIDocument::SetDocTreeHadAudibleMedia()
+{
+  nsIDocument* topLevelDoc = GetTopLevelContentDocument();
+  if (topLevelDoc) {
+    topLevelDoc->mDocTreeHadAudibleMedia = true;
+  }
+}
+
+void
+nsIDocument::SetDocTreeHadPlayRevoked()
+{
+  nsIDocument* topLevelDoc = GetTopLevelContentDocument();
+  if (topLevelDoc) {
+    topLevelDoc->mDocTreeHadPlayRevoked = true;
+  }
+}
+
+void
 nsIDocument::MaybeAllowStorageForOpener()
 {
   if (!StaticPrefs::privacy_restrict3rdpartystorage_enabled()) {
     return;
   }
 
   // This will probably change for project fission, but currently this document
   // and the opener are on the same process. In the future, we should make this

--- a/dom/base/nsIDocument.h
+++ b/dom/base/nsIDocument.h
@@ -3570,16 +3570,20 @@ public:
    * element containing the subdocument containing aFrame, and/or find the
    * nearest non-anonymous ancestor in this document.
    * Returns null if there is no such element.
    */
   nsIContent* GetContentInThisDocument(nsIFrame* aFrame) const;
 
   void ReportShadowDOMUsage();
 
+  // Sets flags for media autoplay telemetry.
+  void SetDocTreeHadAudibleMedia();
+  void SetDocTreeHadPlayRevoked();
+
 protected:
   void DoUpdateSVGUseElementShadowTrees();
 
   already_AddRefed<nsIPrincipal> MaybeDowngradePrincipal(nsIPrincipal* aPrincipal);
 
   void EnsureOnloadBlocker();
 
   void SendToConsole(nsCOMArray<nsISecurityConsoleMessage>& aMessages);
@@ -4091,16 +4095,26 @@ protected:
   // documents (SVG documents) that are not guaranteed to be destroyed, we
   // report use counters when the image cache no longer has any imgRequestProxys
   // pointing to them.  We track whether we ever reported use counters so
   // that we only report them once for the document.
   bool mReportedUseCounters: 1;
 
   bool mHasReportedShadowDOMUsage: 1;
 
+  // True if this document contained, either directly or in a subdocument,
+  // an HTMLMediaElement that played audibly. This should only be set on
+  // top level content documents.
+  bool mDocTreeHadAudibleMedia: 1;
+  // True if this document contained, either directly or in a subdocument,
+  // an HTMLMediaElement that was playing inaudibly and became audible and we
+  // paused the HTMLMediaElement because it wasn't allowed to autoplay audibly.
+  // This should only be set on top level content documents.
+  bool mDocTreeHadPlayRevoked: 1;
+
 #ifdef DEBUG
 public:
   bool mWillReparent: 1;
 protected:
 #endif
 
   uint8_t mPendingFullscreenRequests;
 

--- a/dom/html/HTMLMediaElement.cpp
+++ b/dom/html/HTMLMediaElement.cpp
@@ -3052,16 +3052,17 @@ void
 HTMLMediaElement::PauseIfShouldNotBePlaying()
 {
   if (GetPaused()) {
     return;
   }
   if (AutoplayPolicy::IsAllowedToPlay(*this) != nsIAutoplay::ALLOWED) {
     ErrorResult rv;
     Pause(rv);
+    OwnerDoc()->SetDocTreeHadPlayRevoked();
   }
 }
 
 void
 HTMLMediaElement::SetVolumeInternal()
 {
   float effectiveVolume = ComputedVolume();
 
@@ -3999,16 +4000,31 @@ HTMLMediaElement::NotifyXPCOMShutdown()
 }
 
 bool
 HTMLMediaElement::AudioChannelAgentDelayingPlayback()
 {
   return mAudioChannelWrapper && mAudioChannelWrapper->IsPlaybackBlocked();
 }
 
+void
+HTMLMediaElement::ReportAutoplayTelemetry() const
+{
+  // If we're audible, and autoplaying...
+  if ((Volume() > 0.0 && !Muted()) &&
+      (!OwnerDoc()->HasBeenUserGestureActivated() || Autoplay())) {
+    OwnerDoc()->SetDocTreeHadAudibleMedia();
+    if (AutoplayPolicy::WouldBeAllowedToPlayIfAutoplayDisabled(*this)) {
+      ScalarAdd(Telemetry::ScalarID::MEDIA_AUTOPLAY_WOULD_BE_ALLOWED_COUNT, 1);
+    } else {
+      ScalarAdd(Telemetry::ScalarID::MEDIA_AUTOPLAY_WOULD_NOT_BE_ALLOWED_COUNT, 1);
+    }
+  }
+}
+
 already_AddRefed<Promise>
 HTMLMediaElement::Play(ErrorResult& aRv)
 {
   LOG(LogLevel::Debug,
       ("%p Play() called by JS readyState=%d", this, mReadyState));
 
   // 4.8.12.8
   // When the play() method on a media element is invoked, the user agent must
@@ -4058,16 +4074,18 @@ HTMLMediaElement::Play(ErrorResult& aRv)
     LOG(LogLevel::Debug, ("%p play blocked by AudioChannelAgent.", this));
     promise->MaybeReject(NS_ERROR_DOM_MEDIA_NOT_ALLOWED_ERR);
     if (StaticPrefs::MediaBlockEventEnabled()) {
       DispatchAsyncEvent(NS_LITERAL_STRING("blocked"));
     }
     return promise.forget();
   }
 
+  ReportAutoplayTelemetry();
+
   const bool handlingUserInput = EventStateManager::IsHandlingUserInput();
   switch (AutoplayPolicy::IsAllowedToPlay(*this)) {
     case nsIAutoplay::ALLOWED: {
       mPendingPlayPromises.AppendElement(promise);
       PlayInternal(handlingUserInput);
       UpdateCustomPolicyAfterPlayed();
       break;
     }
@@ -6216,16 +6234,17 @@ HTMLMediaElement::CanActivateAutoplay()
 
 void
 HTMLMediaElement::CheckAutoplayDataReady()
 {
   if (!CanActivateAutoplay()) {
     return;
   }
 
+  ReportAutoplayTelemetry();
   switch (AutoplayPolicy::IsAllowedToPlay(*this)) {
     case nsIAutoplay::BLOCKED:
       return;
     case nsIAutoplay::PROMPT:
       EnsureAutoplayRequested(false);
       return;
     case nsIAutoplay::ALLOWED:
       break;

--- a/dom/html/HTMLMediaElement.h
+++ b/dom/html/HTMLMediaElement.h
@@ -1776,16 +1776,18 @@ public:
     TimeStamp mStartTime;
     TimeDuration mSum;
     uint32_t mCount;
   };
 private:
 
   already_AddRefed<PlayPromise> CreatePlayPromise(ErrorResult& aRv) const;
 
+  void ReportAutoplayTelemetry() const;
+
   /**
    * This function is called by AfterSetAttr and OnAttrSetButNotChanged.
    * It will not be called if the value is being unset.
    *
    * @param aNamespaceID the namespace of the attr being set
    * @param aName the localname of the attribute being set
    * @param aNotify Whether we plan to notify document observers.
    */

--- a/dom/media/AutoplayPolicy.cpp
+++ b/dom/media/AutoplayPolicy.cpp
@@ -95,37 +95,45 @@ DefaultAutoplayBehaviour()
   int prefValue = Preferences::GetInt("media.autoplay.default", nsIAutoplay::ALLOWED);
   if (prefValue < nsIAutoplay::ALLOWED || prefValue > nsIAutoplay::PROMPT) {
     // Invalid pref values are just converted to ALLOWED.
     return nsIAutoplay::ALLOWED;
   }
   return prefValue;
 }
 
+static bool
+IsMediaElementAllowedToPlay(const HTMLMediaElement& aElement)
+{
+  return ((aElement.Volume() == 0.0 || aElement.Muted()) &&
+          Preferences::GetBool("media.autoplay.allow-muted", true)) ||
+         IsWindowAllowedToPlay(aElement.OwnerDoc()->GetInnerWindow());
+}
+
+/* static */ bool
+AutoplayPolicy::WouldBeAllowedToPlayIfAutoplayDisabled(const HTMLMediaElement& aElement)
+{
+  return IsMediaElementAllowedToPlay(aElement);
+}
+
 /* static */ uint32_t
 AutoplayPolicy::IsAllowedToPlay(const HTMLMediaElement& aElement)
 {
   const uint32_t autoplayDefault = DefaultAutoplayBehaviour();
   // TODO : this old way would be removed when user-gestures-needed becomes
   // as a default option to block autoplay.
   if (!Preferences::GetBool("media.autoplay.enabled.user-gestures-needed", false)) {
     // If element is blessed, it would always be allowed to play().
     return (autoplayDefault == nsIAutoplay::ALLOWED ||
             aElement.IsBlessed() ||
             EventStateManager::IsHandlingUserInput())
               ? nsIAutoplay::ALLOWED : nsIAutoplay::BLOCKED;
   }
 
-  // Muted content
-  if ((aElement.Volume() == 0.0 || aElement.Muted()) &&
-      Preferences::GetBool("media.autoplay.allow-muted", true)) {
-    return nsIAutoplay::ALLOWED;
-  }
-
-  if (IsWindowAllowedToPlay(aElement.OwnerDoc()->GetInnerWindow())) {
+  if (IsMediaElementAllowedToPlay(aElement)) {
     return nsIAutoplay::ALLOWED;
   }
 
   return autoplayDefault;
 }
 
 /* static */ bool
 AutoplayPolicy::IsAudioContextAllowedToPlay(NotNull<AudioContext*> aContext)

--- a/dom/media/AutoplayPolicy.h
+++ b/dom/media/AutoplayPolicy.h
@@ -33,16 +33,23 @@ class AudioContext;
  * 3) Document's origin has the "autoplay-media" permission.
  */
 class AutoplayPolicy
 {
 public:
   // Returns whether a given media element is allowed to play.
   static uint32_t IsAllowedToPlay(const HTMLMediaElement& aElement);
 
+  // Returns true if a given media element would be allowed to play
+  // if block autoplay was enabled. If this returns false, it means we would
+  // either block or ask for permission.
+  // Note: this is for telemetry purposes, and doesn't check the prefs
+  // which enable/disable block autoplay. Do not use for blocking logic!
+  static bool WouldBeAllowedToPlayIfAutoplayDisabled(const HTMLMediaElement& aElement);
+
   // Returns whether a given AudioContext is allowed to play.
   static bool IsAudioContextAllowedToPlay(NotNull<AudioContext*> aContext);
 
   // Returns the AutoplayPermissionManager that a given document must request on
   // for autoplay permission.
   static already_AddRefed<AutoplayPermissionManager> RequestFor(
     const nsIDocument& aDocument);
 };

--- a/toolkit/components/telemetry/Scalars.yaml
+++ b/toolkit/components/telemetry/Scalars.yaml
@@ -752,16 +752,97 @@ mediarecorder:
     kind: uint
     notification_emails:
       - bvandyk@mozilla.com
     release_channel_collection: opt-in
     record_in_processes:
       - main
       - content
 
+media:
+  page_count:
+    bug_numbers:
+      - 1476456
+    description: >
+      The number of times a top level document is loaded.
+    expires: "68"
+    kind: uint
+    notification_emails:
+      - cpearce@mozilla.com
+      - alwu@mozilla.com
+      - nohlmeier@mozilla.com
+    release_channel_collection: opt-in
+    record_in_processes:
+      - main
+      - content
+
+  page_had_media_count:
+    bug_numbers:
+      - 1476456
+    description: >
+      The number of times a document hierarchy contained at least one audible HTMLMediaElement that had play() called upon it.
+    expires: "68"
+    kind: uint
+    notification_emails:
+      - cpearce@mozilla.com
+      - alwu@mozilla.com
+      - nohlmeier@mozilla.com
+    release_channel_collection: opt-in
+    record_in_processes:
+      - main
+      - content
+
+  page_had_play_revoked_count:
+    bug_numbers:
+      - 1476456
+    description: >
+      The number of times a document hierarchy contained at least one muted playing HTMLMediaElement that was paused due to becoming unmuted while not being allowed to autoplay.
+    expires: "68"
+    kind: uint
+    notification_emails:
+      - cpearce@mozilla.com
+      - alwu@mozilla.com
+      - nohlmeier@mozilla.com
+    release_channel_collection: opt-in
+    record_in_processes:
+      - main
+      - content
+
+  autoplay_would_not_be_allowed_count:
+    bug_numbers:
+      - 1476456
+    description: >
+      The number of HTMLMediaElement autoplays on audible HTMLMediaElements which would not be allowed to play if block autoplay was enabled; we'd either prompt for permission to play or block outright depending on user preferences.
+    expires: "68"
+    kind: uint
+    notification_emails:
+      - cpearce@mozilla.com
+      - alwu@mozilla.com
+      - nohlmeier@mozilla.com
+    release_channel_collection: opt-in
+    record_in_processes:
+      - main
+      - content
+
+  autoplay_would_be_allowed_count:
+    bug_numbers:
+      - 1476456
+    description: >
+      The number of HTMLMediaElement autoplays on audible HTMLMediaElements that would have been allowed (not blocked) by the autoplay policy if block autoplay was enabled.
+    expires: "68"
+    kind: uint
+    notification_emails:
+      - cpearce@mozilla.com
+      - alwu@mozilla.com
+      - nohlmeier@mozilla.com
+    release_channel_collection: opt-in
+    record_in_processes:
+      - main
+      - content
+
 # The following section contains content process base counters.
 dom.contentprocess:
   troubled_due_to_memory:
     bug_numbers:
       - 1305091
     description: >
       The number of content processes that were marked as troubled because
       it was running low on virtual memory.