--- a/dom/html/HTMLMediaElement.cpp
+++ b/dom/html/HTMLMediaElement.cpp
@@ -122,16 +122,20 @@
 #include "xpcpublic.h"
 #include <algorithm>
 #include <cmath>
 #include <limits>
 
 mozilla::LazyLogModule gMediaElementLog("nsMediaElement");
 static mozilla::LazyLogModule gMediaElementEventsLog("nsMediaElementEvents");
 
+extern mozilla::LazyLogModule gAutoplayPermissionLog;
+#define AUTOPLAY_LOG(msg, ...)                                             \
+  MOZ_LOG(gAutoplayPermissionLog, LogLevel::Debug, (msg, ##__VA_ARGS__))
+
 #define LOG(type, msg) MOZ_LOG(gMediaElementLog, type, msg)
 #define LOG_EVENT(type, msg) MOZ_LOG(gMediaElementEventsLog, type, msg)
 
 using namespace mozilla::layers;
 using mozilla::net::nsMediaFragmentURIParser;
 using namespace mozilla::dom::HTMLMediaElement_Binding;
 
 namespace mozilla {
@@ -3057,16 +3061,17 @@ HTMLMediaElement::SetMutedInternal(uint3
 
 void
 HTMLMediaElement::PauseIfShouldNotBePlaying()
 {
   if (GetPaused()) {
     return;
   }
   if (AutoplayPolicy::IsAllowedToPlay(*this) != nsIAutoplay::ALLOWED) {
+    AUTOPLAY_LOG("pause because not allowed to play, element=%p", this);
     ErrorResult rv;
     Pause(rv);
     OwnerDoc()->SetDocTreeHadPlayRevoked();
   }
 }
 
 void
 HTMLMediaElement::SetVolumeInternal()

--- a/dom/media/AutoplayPolicy.cpp
+++ b/dom/media/AutoplayPolicy.cpp
@@ -2,29 +2,50 @@
 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this file,
  * You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #include "AutoplayPolicy.h"
 
 #include "mozilla/EventStateManager.h"
+#include "mozilla/Logging.h"
 #include "mozilla/Preferences.h"
 #include "mozilla/dom/AudioContext.h"
 #include "mozilla/AutoplayPermissionManager.h"
 #include "mozilla/dom/HTMLMediaElement.h"
 #include "mozilla/dom/HTMLMediaElementBinding.h"
 #include "nsIAutoplay.h"
 #include "nsContentUtils.h"
 #include "nsIDocument.h"
 #include "MediaManager.h"
 #include "nsIDocShell.h"
 #include "nsIDocShellTreeItem.h"
 #include "nsPIDOMWindow.h"
 
+mozilla::LazyLogModule gAutoplayPermissionLog("Autoplay");
+
+#define AUTOPLAY_LOG(msg, ...)                                             \
+  MOZ_LOG(gAutoplayPermissionLog, LogLevel::Debug, (msg, ##__VA_ARGS__))
+
+static const char*
+AllowAutoplayToStr(const uint32_t state)
+{
+  switch (state) {
+    case nsIAutoplay::ALLOWED:
+      return "allowed";
+    case nsIAutoplay::BLOCKED:
+      return "blocked";
+    case nsIAutoplay::PROMPT:
+      return "prompt";
+    default:
+      return "unknown";
+  }
+}
+
 namespace mozilla {
 namespace dom {
 
 static nsIDocument*
 ApproverDocOf(const nsIDocument& aDocument)
 {
   nsCOMPtr<nsIDocShell> ds = aDocument.GetDocShell();
   if (!ds) {
@@ -57,27 +78,27 @@ IsWindowAllowedToPlay(nsPIDOMWindowInner
 
   if (!aWindow->GetExtantDoc()) {
     return false;
   }
 
   nsIDocument* approver = ApproverDocOf(*aWindow->GetExtantDoc());
   if (nsContentUtils::IsExactSitePermAllow(approver->NodePrincipal(),
                                            "autoplay-media")) {
-    // Autoplay permission has been granted already.
+    AUTOPLAY_LOG("Allow autoplay as document has autoplay permission.");
     return true;
   }
 
   if (approver->HasBeenUserGestureActivated()) {
-    // Document has been activated by user gesture.
+    AUTOPLAY_LOG("Allow autoplay as document activated by user gesture.");
     return true;
   }
 
   if (approver->IsExtensionPage()) {
-    // Always allow extension page to autoplay.
+    AUTOPLAY_LOG("Allow autoplay as in extension document.");
     return true;
   }
 
   return false;
 }
 
 /* static */
 already_AddRefed<AutoplayPermissionManager>
@@ -103,20 +124,33 @@ DefaultAutoplayBehaviour()
     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()) ||
-          (aElement.OwnerDoc()->MediaDocumentKind() == nsIDocument::MediaDocumentKind::Video);
+  if ((aElement.Volume() == 0.0 || aElement.Muted()) &&
+       Preferences::GetBool("media.autoplay.allow-muted", true)) {
+    AUTOPLAY_LOG("Allow muted media %p to autoplay.", &aElement);
+    return true;
+  }
+
+  if (IsWindowAllowedToPlay(aElement.OwnerDoc()->GetInnerWindow())) {
+    AUTOPLAY_LOG("Autoplay allowed as activated/whitelisted window, media %p.", &aElement);
+    return true;
+  }
+
+  if (aElement.OwnerDoc()->MediaDocumentKind() == nsIDocument::MediaDocumentKind::Video) {
+    AUTOPLAY_LOG("Allow video document %p to autoplay\n", &aElement);
+    return true;
+  }
+
+  return false;
 }
 
 /* static */ bool
 AutoplayPolicy::WouldBeAllowedToPlayIfAutoplayDisabled(const HTMLMediaElement& aElement)
 {
   return IsMediaElementAllowedToPlay(aElement);
 }
 
@@ -129,21 +163,22 @@ AutoplayPolicy::IsAllowedToPlay(const HT
   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;
   }
 
-  if (IsMediaElementAllowedToPlay(aElement)) {
-    return nsIAutoplay::ALLOWED;
-  }
+  const uint32_t result = IsMediaElementAllowedToPlay(aElement) ?
+    nsIAutoplay::ALLOWED : autoplayDefault;
 
-  return autoplayDefault;
+  AUTOPLAY_LOG("IsAllowedToPlay, mediaElement=%p, isAllowToPlay=%s",
+                &aElement, AllowAutoplayToStr(result));
+  return result;
 }
 
 /* static */ bool
 AutoplayPolicy::IsAudioContextAllowedToPlay(NotNull<AudioContext*> aContext)
 {
   if (!Preferences::GetBool("media.autoplay.block-webaudio", false)) {
     return true;
   }