--- a/dom/base/nsDOMWindowUtils.cpp
+++ b/dom/base/nsDOMWindowUtils.cpp
@@ -4225,17 +4225,17 @@ nsDOMWindowUtils::IsTimeoutTracking(uint
 
 struct StateTableEntry
 {
   const char* mStateString;
   EventStates mState;
 };
 
 static constexpr StateTableEntry kManuallyManagedStates[] = {
-  // none yet; but for example: { "highlight", NS_EVENT_STATE_HIGHLIGHT },
+  { "-moz-autofill", NS_EVENT_STATE_AUTOFILL },
   { nullptr, EventStates() },
 };
 
 static_assert(!kManuallyManagedStates[ArrayLength(kManuallyManagedStates) - 1]
                .mStateString,
               "last kManuallyManagedStates entry must be a sentinel with "
               "mStateString == nullptr");
 

--- a/dom/events/EventStates.h
+++ b/dom/events/EventStates.h
@@ -283,16 +283,18 @@ private:
 // Handler for click to play plugin (vulnerable w/no update)
 #define NS_EVENT_STATE_VULNERABLE_NO_UPDATE NS_DEFINE_EVENT_STATE_MACRO(42)
 // Element has focus-within.
 #define NS_EVENT_STATE_FOCUS_WITHIN NS_DEFINE_EVENT_STATE_MACRO(43)
 // Element is ltr (for :dir pseudo-class)
 #define NS_EVENT_STATE_LTR NS_DEFINE_EVENT_STATE_MACRO(44)
 // Element is rtl (for :dir pseudo-class)
 #define NS_EVENT_STATE_RTL NS_DEFINE_EVENT_STATE_MACRO(45)
+// Element is filled by Autofill feature.
+#define NS_EVENT_STATE_AUTOFILL NS_DEFINE_EVENT_STATE_MACRO(50)
 
 // Event state that is used for values that need to be parsed but do nothing.
 #define NS_EVENT_STATE_IGNORE NS_DEFINE_EVENT_STATE_MACRO(63)
 
 /**
  * NOTE: do not go over 63 without updating EventStates::InternalType!
  */
 
@@ -301,17 +303,17 @@ private:
 // Event states that can be added and removed through
 // Element::{Add,Remove}ManuallyManagedStates.
 //
 // Take care when manually managing state bits.  You are responsible for
 // setting or clearing the bit when an Element is added or removed from a
 // document (e.g. in BindToTree and UnbindFromTree), if that is an
 // appropriate thing to do for your state bit.
 #define MANUALLY_MANAGED_STATES (             \
-  mozilla::EventStates() /* none so far */    \
+  NS_EVENT_STATE_AUTOFILL                     \
 )
 
 // Event states that are managed externally to an element (by the
 // EventStateManager, or by other code).  As opposed to those in
 // INTRINSIC_STATES, which are are computed by the element itself
 // and returned from Element::IntrinsicState.
 #define EXTERNALLY_MANAGED_STATES (           \
   MANUALLY_MANAGED_STATES |                   \

--- a/layout/style/nsCSSPseudoClassList.h
+++ b/layout/style/nsCSSPseudoClassList.h
@@ -203,16 +203,20 @@ CSS_STATE_PSEUDO_CLASS(mozHandlerBlocked
 CSS_STATE_PSEUDO_CLASS(mozHandlerCrashed, ":-moz-handler-crashed",
                        CSS_PSEUDO_CLASS_ENABLED_IN_UA_SHEETS_AND_CHROME, "",
                        NS_EVENT_STATE_HANDLER_CRASHED)
 
 CSS_STATE_PSEUDO_CLASS(mozMathIncrementScriptLevel,
                        ":-moz-math-increment-script-level", 0, "",
                        NS_EVENT_STATE_INCREMENT_SCRIPT_LEVEL)
 
+CSS_STATE_PSEUDO_CLASS(mozAutofill, ":-moz-autofill",
+                       CSS_PSEUDO_CLASS_ENABLED_IN_UA_SHEETS_AND_CHROME, "",
+                       NS_EVENT_STATE_AUTOFILL)
+
 // CSS 3 UI
 // http://www.w3.org/TR/2004/CR-css3-ui-20040511/#pseudo-classes
 CSS_STATE_PSEUDO_CLASS(required, ":required", 0, "", NS_EVENT_STATE_REQUIRED)
 CSS_STATE_PSEUDO_CLASS(optional, ":optional", 0, "", NS_EVENT_STATE_OPTIONAL)
 CSS_STATE_PSEUDO_CLASS(valid, ":valid", 0, "", NS_EVENT_STATE_VALID)
 CSS_STATE_PSEUDO_CLASS(invalid, ":invalid", 0, "", NS_EVENT_STATE_INVALID)
 CSS_STATE_PSEUDO_CLASS(inRange, ":in-range", 0, "", NS_EVENT_STATE_INRANGE)
 CSS_STATE_PSEUDO_CLASS(outOfRange, ":out-of-range", 0, "", NS_EVENT_STATE_OUTOFRANGE)

--- a/layout/style/res/forms.css
+++ b/layout/style/res/forms.css
@@ -1204,8 +1204,12 @@ input[type=number]::-moz-number-spin-dow
   border-bottom-left-radius: 4px;
   border-bottom-right-radius: 4px;
 }
 
 input[type="number"] > div > div > div:hover {
   /* give some indication of hover state for the up/down buttons */
   background-color: lightblue;
 }
+
+:-moz-autofill {
+  filter: grayscale(21%) brightness(88%) contrast(161%) invert(10%) sepia(40%) saturate(206%);
+}