--- a/layout/base/nsPresShell.cpp
+++ b/layout/base/nsPresShell.cpp
@@ -87,16 +87,17 @@
 #include "nsIDOMHTMLDocument.h"
 #include "nsFrameManager.h"
 #include "nsXPCOM.h"
 #include "nsILayoutHistoryState.h"
 #include "nsILineIterator.h" // for ScrollContentIntoView
 #include "PLDHashTable.h"
 #include "mozilla/dom/BeforeAfterKeyboardEventBinding.h"
 #include "mozilla/dom/Touch.h"
+#include "mozilla/dom/TouchEvent.h"
 #include "mozilla/dom/PointerEventBinding.h"
 #include "nsIObserverService.h"
 #include "nsDocShell.h"        // for reflow observation
 #include "nsIBaseWindow.h"
 #include "nsError.h"
 #include "nsLayoutUtils.h"
 #include "nsViewportInfo.h"
 #include "nsCSSRendering.h"
@@ -729,27 +730,39 @@ nsIPresShell::FrameSelection()
 }
 
 //----------------------------------------------------------------------
 
 static bool sSynthMouseMove = true;
 static uint32_t sNextPresShellId;
 static bool sPointerEventEnabled = true;
 static bool sAccessibleCaretEnabled = false;
+static bool sAccessibleCaretOnTouch = false;
 static bool sBeforeAfterKeyboardEventEnabled = false;
 
 /* static */ bool
-PresShell::AccessibleCaretEnabled()
+PresShell::AccessibleCaretEnabled(nsIDocShell* aDocShell)
 {
   static bool initialized = false;
   if (!initialized) {
     Preferences::AddBoolVarCache(&sAccessibleCaretEnabled, "layout.accessiblecaret.enabled");
+    Preferences::AddBoolVarCache(&sAccessibleCaretOnTouch, "layout.accessiblecaret.enable_on_touch");
     initialized = true;
   }
-  return sAccessibleCaretEnabled;
+  // If the pref forces it on, then enable it.
+  if (sAccessibleCaretEnabled) {
+    return true;
+  }
+  // If the touch pref is on, and touch events are enabled (this depends
+  // on the specific device running), then enable it.
+  if (sAccessibleCaretOnTouch && dom::TouchEvent::PrefEnabled(aDocShell)) {
+    return true;
+  }
+  // Otherwise, disabled.
+  return false;
 }
 
 /* static */ bool
 PresShell::BeforeAfterKeyboardEventEnabled()
 {
   static bool sInitialized = false;
   if (!sInitialized) {
     Preferences::AddBoolVarCache(&sBeforeAfterKeyboardEventEnabled,
@@ -893,17 +906,17 @@ PresShell::Init(nsIDocument* aDocument,
   // Notify our prescontext that it now has a compatibility mode.  Note that
   // this MUST happen after we set up our style set but before we create any
   // frames.
   mPresContext->CompatibilityModeChanged();
 
   // Add the preference style sheet.
   UpdatePreferenceStyles();
 
-  if (AccessibleCaretEnabled()) {
+  if (AccessibleCaretEnabled(mDocument->GetDocShell())) {
     // Need to happen before nsFrameSelection has been set up.
     mAccessibleCaretEventHub = new AccessibleCaretEventHub(this);
   }
 
   mSelection = new nsFrameSelection();
 
   mSelection->Init(this, nullptr);
 
@@ -7598,17 +7611,17 @@ PresShell::HandleEvent(nsIFrame* aFrame,
   if (mIsDestroying ||
       (sDisableNonTestMouseEvents && !aEvent->mFlags.mIsSynthesizedForTests &&
        aEvent->HasMouseEventMessage())) {
     return NS_OK;
   }
 
   RecordMouseLocation(aEvent);
 
-  if (AccessibleCaretEnabled()) {
+  if (AccessibleCaretEnabled(mDocument->GetDocShell())) {
     // We have to target the focus window because regardless of where the
     // touch goes, we want to access the copy paste manager.
     nsCOMPtr<nsPIDOMWindowOuter> window = GetFocusedDOMWindowInOurWindow();
     nsCOMPtr<nsIDocument> retargetEventDoc =
       window ? window->GetExtantDoc() : nullptr;
     nsCOMPtr<nsIPresShell> presShell =
       retargetEventDoc ? retargetEventDoc->GetShell() : nullptr;
 

--- a/layout/base/nsPresShell.h
+++ b/layout/base/nsPresShell.h
@@ -35,16 +35,17 @@
 #include "mozilla/Attributes.h"
 #include "mozilla/EventForwards.h"
 #include "mozilla/MemoryReporting.h"
 #include "mozilla/StyleSetHandle.h"
 #include "mozilla/UniquePtr.h"
 #include "MobileViewportManager.h"
 #include "ZoomConstraintsClient.h"
 
+class nsIDocShell;
 class nsRange;
 
 struct RangePaintInfo;
 struct nsCallbackEventRequest;
 #ifdef MOZ_REFLOW_PERF
 class ReflowCountMgr;
 #endif
 
@@ -89,17 +90,17 @@ class PresShell final : public nsIPresSh
 public:
   PresShell();
 
   NS_DECL_AND_IMPL_ZEROING_OPERATOR_NEW
 
   // nsISupports
   NS_DECL_ISUPPORTS
 
-  static bool AccessibleCaretEnabled();
+  static bool AccessibleCaretEnabled(nsIDocShell* aDocShell);
 
   // BeforeAfterKeyboardEvent preference
   static bool BeforeAfterKeyboardEventEnabled();
 
   static bool IsTargetIframe(nsINode* aTarget);
 
   void Init(nsIDocument* aDocument, nsPresContext* aPresContext,
             nsViewManager* aViewManager, mozilla::StyleSetHandle aStyleSet);

--- a/modules/libpref/init/all.js
+++ b/modules/libpref/init/all.js
@@ -5159,16 +5159,26 @@ pref("browser.safebrowsing.id", "Firefox
 #endif
 
 // Turn off Spatial navigation by default.
 pref("snav.enabled", false);
 
 // New implementation to unify touch-caret and selection-carets.
 pref("layout.accessiblecaret.enabled", false);
 
+// On Nightly, enable the accessible caret on platforms/devices
+// that we detect have touch support. Note that this pref is an
+// additional way to enable the accessible carets, rather than
+// overriding the layout.accessiblecaret.enabled pref.
+#ifdef NIGHTLY_BUILD
+pref("layout.accessiblecaret.enable_on_touch", true);
+#else
+pref("layout.accessiblecaret.enable_on_touch", false);
+#endif
+
 // CSS attributes of the AccessibleCaret in CSS pixels.
 pref("layout.accessiblecaret.width", "34.0");
 pref("layout.accessiblecaret.height", "36.0");
 pref("layout.accessiblecaret.margin-left", "-18.5");
 pref("layout.accessiblecaret.bar.width", "2.0");
 
 // Show no selection bars at the two ends of the selection highlight.
 pref("layout.accessiblecaret.bar.enabled", false);