diff --git a/packages/core-js/internals/iterator-create-proxy.js b/packages/core-js/internals/iterator-create-proxy.js
index 8245828a7c17..7073d8afadc7 100644
--- a/packages/core-js/internals/iterator-create-proxy.js
+++ b/packages/core-js/internals/iterator-create-proxy.js
@@ -75,6 +75,7 @@ module.exports = function (nextHandler, IS_ITERATOR) {
     } else state = record;
     state.type = ITERATOR_PROXY;
     state.nextHandler = nextHandler;
+    state.counter = 0;
     state.done = false;
     setInternalState(this, state);
   };
diff --git a/packages/core-js/modules/esnext.iterator.every.js b/packages/core-js/modules/esnext.iterator.every.js
index 2ddd445f26d7..f7fbe35c5d19 100644
--- a/packages/core-js/modules/esnext.iterator.every.js
+++ b/packages/core-js/modules/esnext.iterator.every.js
@@ -8,9 +8,10 @@ var getIteratorDirect = require('../internals/get-iterator-direct');
 $({ target: 'Iterator', proto: true, real: true, forced: true }, {
   every: function every(fn) {
     var record = getIteratorDirect(this);
+    var counter = 0;
     aCallable(fn);
     return !iterate(record, function (value, stop) {
-      if (!fn(value)) return stop();
+      if (!fn(value, counter++)) return stop();
     }, { IS_RECORD: true, INTERRUPTED: true }).stopped;
   }
 });
diff --git a/packages/core-js/modules/esnext.iterator.filter.js b/packages/core-js/modules/esnext.iterator.filter.js
index d3205885065f..fb8081e959ce 100644
--- a/packages/core-js/modules/esnext.iterator.filter.js
+++ b/packages/core-js/modules/esnext.iterator.filter.js
@@ -18,7 +18,7 @@ var IteratorProxy = createIteratorProxy(function () {
     done = this.done = !!result.done;
     if (done) return;
     value = result.value;
-    if (callWithSafeIterationClosing(iterator, filterer, value)) return value;
+    if (callWithSafeIterationClosing(iterator, filterer, [value, this.counter++], true)) return value;
   }
 });
 
diff --git a/packages/core-js/modules/esnext.iterator.find.js b/packages/core-js/modules/esnext.iterator.find.js
index 25096bf4a89e..39a0e1308a77 100644
--- a/packages/core-js/modules/esnext.iterator.find.js
+++ b/packages/core-js/modules/esnext.iterator.find.js
@@ -8,9 +8,10 @@ var getIteratorDirect = require('../internals/get-iterator-direct');
 $({ target: 'Iterator', proto: true, real: true, forced: true }, {
   find: function find(fn) {
     var record = getIteratorDirect(this);
+    var counter = 0;
     aCallable(fn);
     return iterate(record, function (value, stop) {
-      if (fn(value)) return stop(value);
+      if (fn(value, counter++)) return stop(value);
     }, { IS_RECORD: true, INTERRUPTED: true }).result;
   }
 });
diff --git a/packages/core-js/modules/esnext.iterator.flat-map.js b/packages/core-js/modules/esnext.iterator.flat-map.js
index e30abcc4a142..9f45e49a75e1 100644
--- a/packages/core-js/modules/esnext.iterator.flat-map.js
+++ b/packages/core-js/modules/esnext.iterator.flat-map.js
@@ -28,7 +28,7 @@ var IteratorProxy = createIteratorProxy(function () {
     if (this.done = !!result.done) return;
 
     try {
-      mapped = mapper(result.value);
+      mapped = mapper(result.value, this.counter++);
       iteratorMethod = getIteratorMethod(mapped);
 
       if (!iteratorMethod) {
diff --git a/packages/core-js/modules/esnext.iterator.for-each.js b/packages/core-js/modules/esnext.iterator.for-each.js
index ffc40963dfcb..107f778d4209 100644
--- a/packages/core-js/modules/esnext.iterator.for-each.js
+++ b/packages/core-js/modules/esnext.iterator.for-each.js
@@ -2,10 +2,16 @@
 // https://github.com/tc39/proposal-iterator-helpers
 var $ = require('../internals/export');
 var iterate = require('../internals/iterate');
+var aCallable = require('../internals/a-callable');
 var getIteratorDirect = require('../internals/get-iterator-direct');
 
 $({ target: 'Iterator', proto: true, real: true, forced: true }, {
   forEach: function forEach(fn) {
-    iterate(getIteratorDirect(this), fn, { IS_RECORD: true });
+    var record = getIteratorDirect(this);
+    var counter = 0;
+    aCallable(fn);
+    iterate(record, function (value) {
+      fn(value, counter++);
+    }, { IS_RECORD: true });
   }
 });
diff --git a/packages/core-js/modules/esnext.iterator.indexed.js b/packages/core-js/modules/esnext.iterator.indexed.js
index b68c9fc12bd9..ed3eb16641cb 100644
--- a/packages/core-js/modules/esnext.iterator.indexed.js
+++ b/packages/core-js/modules/esnext.iterator.indexed.js
@@ -1,3 +1,4 @@
+// TODO: Remove from `core-js@4`
 // https://github.com/tc39/proposal-iterator-helpers
 var $ = require('../internals/export');
 var indexed = require('../internals/iterator-indexed');
diff --git a/packages/core-js/modules/esnext.iterator.map.js b/packages/core-js/modules/esnext.iterator.map.js
index c1b4b1963ab2..fc68061228af 100644
--- a/packages/core-js/modules/esnext.iterator.map.js
+++ b/packages/core-js/modules/esnext.iterator.map.js
@@ -12,7 +12,7 @@ var IteratorProxy = createIteratorProxy(function () {
   var iterator = this.iterator;
   var result = anObject(call(this.next, iterator));
   var done = this.done = !!result.done;
-  if (!done) return callWithSafeIterationClosing(iterator, this.mapper, result.value);
+  if (!done) return callWithSafeIterationClosing(iterator, this.mapper, [result.value, this.counter++], true);
 });
 
 $({ target: 'Iterator', proto: true, real: true, forced: true }, {
diff --git a/packages/core-js/modules/esnext.iterator.reduce.js b/packages/core-js/modules/esnext.iterator.reduce.js
index b046d8f66bdf..ca4587d56822 100644
--- a/packages/core-js/modules/esnext.iterator.reduce.js
+++ b/packages/core-js/modules/esnext.iterator.reduce.js
@@ -13,13 +13,15 @@ $({ target: 'Iterator', proto: true, real: true, forced: true }, {
     aCallable(reducer);
     var noInitial = arguments.length < 2;
     var accumulator = noInitial ? undefined : arguments[1];
+    var counter = 0;
     iterate(record, function (value) {
       if (noInitial) {
         noInitial = false;
         accumulator = value;
       } else {
-        accumulator = reducer(accumulator, value);
+        accumulator = reducer(accumulator, value, counter);
       }
+      counter++;
     }, { IS_RECORD: true });
     if (noInitial) throw $TypeError('Reduce of empty iterator with no initial value');
     return accumulator;
diff --git a/packages/core-js/modules/esnext.iterator.some.js b/packages/core-js/modules/esnext.iterator.some.js
index 660ef02c5c1d..a679e2dba3ca 100644
--- a/packages/core-js/modules/esnext.iterator.some.js
+++ b/packages/core-js/modules/esnext.iterator.some.js
@@ -8,9 +8,10 @@ var getIteratorDirect = require('../internals/get-iterator-direct');
 $({ target: 'Iterator', proto: true, real: true, forced: true }, {
   some: function some(fn) {
     var record = getIteratorDirect(this);
+    var counter = 0;
     aCallable(fn);
     return iterate(record, function (value, stop) {
-      if (fn(value)) return stop();
+      if (fn(value, counter++)) return stop();
     }, { IS_RECORD: true, INTERRUPTED: true }).stopped;
   }
 });
diff --git a/tests/pure/esnext.iterator.every.js b/tests/pure/esnext.iterator.every.js
index 2c58bac90392..be836c72bc8d 100644
--- a/tests/pure/esnext.iterator.every.js
+++ b/tests/pure/esnext.iterator.every.js
@@ -12,10 +12,11 @@ QUnit.test('Iterator#every', assert => {
 
   assert.true(every.call(createIterator([1, 2, 3]), it => typeof it == 'number'), 'basic functionality #1');
   assert.false(every.call(createIterator([1, 2, 3]), it => it % 2), 'basic functionality #2');
-  every.call(createIterator([1]), function (arg) {
+  every.call(createIterator([1]), function (arg, counter) {
     assert.same(this, STRICT_THIS, 'this');
-    assert.same(arguments.length, 1, 'arguments length');
+    assert.same(arguments.length, 2, 'arguments length');
     assert.same(arg, 1, 'argument');
+    assert.same(counter, 0, 'counter');
   });
 
   assert.throws(() => every.call(undefined, () => { /* empty */ }), TypeError);
diff --git a/tests/pure/esnext.iterator.filter.js b/tests/pure/esnext.iterator.filter.js
index 65b7afdac8c9..fa48a11a57b0 100644
--- a/tests/pure/esnext.iterator.filter.js
+++ b/tests/pure/esnext.iterator.filter.js
@@ -11,10 +11,11 @@ QUnit.test('Iterator#filter', assert => {
   assert.nonEnumerable(Iterator.prototype, 'filter');
 
   assert.arrayEqual(filter.call(createIterator([1, 2, 3]), it => it % 2).toArray(), [1, 3], 'basic functionality');
-  filter.call(createIterator([1]), function (arg) {
+  filter.call(createIterator([1]), function (arg, counter) {
     assert.same(this, STRICT_THIS, 'this');
-    assert.same(arguments.length, 1, 'arguments length');
+    assert.same(arguments.length, 2, 'arguments length');
     assert.same(arg, 1, 'argument');
+    assert.same(counter, 0, 'counter');
   }).toArray();
 
   assert.throws(() => filter.call(undefined, () => { /* empty */ }), TypeError);
diff --git a/tests/pure/esnext.iterator.find.js b/tests/pure/esnext.iterator.find.js
index 6e9c9f0eab7d..049b2b51564d 100644
--- a/tests/pure/esnext.iterator.find.js
+++ b/tests/pure/esnext.iterator.find.js
@@ -11,10 +11,11 @@ QUnit.test('Iterator#find', assert => {
   assert.nonEnumerable(Iterator.prototype, 'find');
 
   assert.same(find.call(createIterator([1, 2, 3]), it => !(it % 2)), 2, 'basic functionality');
-  find.call(createIterator([1]), function (arg) {
+  find.call(createIterator([1]), function (arg, counter) {
     assert.same(this, STRICT_THIS, 'this');
-    assert.same(arguments.length, 1, 'arguments length');
+    assert.same(arguments.length, 2, 'arguments length');
     assert.same(arg, 1, 'argument');
+    assert.same(counter, 0, 'counter');
   });
 
   assert.throws(() => find.call(undefined, () => { /* empty */ }), TypeError);
diff --git a/tests/pure/esnext.iterator.flat-map.js b/tests/pure/esnext.iterator.flat-map.js
index 70e55fdc6d0b..123bbe408be9 100644
--- a/tests/pure/esnext.iterator.flat-map.js
+++ b/tests/pure/esnext.iterator.flat-map.js
@@ -15,10 +15,11 @@ QUnit.test('Iterator#flatMap', assert => {
     [-1, -2, 3, 4, 5, 6, 'a', 'b'],
     'basic functionality',
   );
-  flatMap.call(createIterator([1]), function (arg) {
+  flatMap.call(createIterator([1]), function (arg, counter) {
     assert.same(this, STRICT_THIS, 'this');
-    assert.same(arguments.length, 1, 'arguments length');
+    assert.same(arguments.length, 2, 'arguments length');
     assert.same(arg, 1, 'argument');
+    assert.same(counter, 0, 'counter');
     return [arg];
   }).toArray();
 
diff --git a/tests/pure/esnext.iterator.for-each.js b/tests/pure/esnext.iterator.for-each.js
index 6afb6531482a..ad965bbc0ec7 100644
--- a/tests/pure/esnext.iterator.for-each.js
+++ b/tests/pure/esnext.iterator.for-each.js
@@ -16,10 +16,11 @@ QUnit.test('Iterator#forEach', assert => {
 
   assert.arrayEqual(array, [1, 2, 3], 'basic functionality');
 
-  forEach.call(createIterator([1]), function (arg) {
+  forEach.call(createIterator([1]), function (arg, counter) {
     assert.same(this, STRICT_THIS, 'this');
-    assert.same(arguments.length, 1, 'arguments length');
+    assert.same(arguments.length, 2, 'arguments length');
     assert.same(arg, 1, 'argument');
+    assert.same(counter, 0, 'counter');
   });
 
   assert.throws(() => forEach.call(undefined, () => { /* empty */ }), TypeError);
diff --git a/tests/pure/esnext.iterator.map.js b/tests/pure/esnext.iterator.map.js
index 67b48dfb2294..a3dfed410744 100644
--- a/tests/pure/esnext.iterator.map.js
+++ b/tests/pure/esnext.iterator.map.js
@@ -11,10 +11,11 @@ QUnit.test('Iterator#map', assert => {
   assert.nonEnumerable(Iterator.prototype, 'map');
 
   assert.arrayEqual(map.call(createIterator([1, 2, 3]), it => it ** 2).toArray(), [1, 4, 9], 'basic functionality');
-  map.call(createIterator([1]), function (arg) {
+  map.call(createIterator([1]), function (arg, counter) {
     assert.same(this, STRICT_THIS, 'this');
-    assert.same(arguments.length, 1, 'arguments length');
+    assert.same(arguments.length, 2, 'arguments length');
     assert.same(arg, 1, 'argument');
+    assert.same(counter, 0, 'counter');
   }).toArray();
 
   assert.throws(() => map.call(undefined, () => { /* empty */ }), TypeError);
diff --git a/tests/pure/esnext.iterator.reduce.js b/tests/pure/esnext.iterator.reduce.js
index 4951a79733e3..15dc7c2f812e 100644
--- a/tests/pure/esnext.iterator.reduce.js
+++ b/tests/pure/esnext.iterator.reduce.js
@@ -12,11 +12,12 @@ QUnit.test('Iterator#reduce', assert => {
 
   assert.same(reduce.call(createIterator([1, 2, 3]), (a, b) => a + b, 1), 7, 'basic functionality');
   assert.same(reduce.call(createIterator([1, 2, 3]), (a, b) => a + b), 6, 'basic functionality, no init');
-  reduce.call(createIterator([2]), function (a, b) {
+  reduce.call(createIterator([2]), function (a, b, counter) {
     assert.same(this, STRICT_THIS, 'this');
-    assert.same(arguments.length, 2, 'arguments length');
+    assert.same(arguments.length, 3, 'arguments length');
     assert.same(a, 1, 'argument 1');
     assert.same(b, 2, 'argument 2');
+    assert.same(counter, 0, 'counter');
   }, 1);
 
   assert.throws(() => reduce.call(undefined, (a, b) => a + b, 0), TypeError);
diff --git a/tests/pure/esnext.iterator.some.js b/tests/pure/esnext.iterator.some.js
index a8c1d4c8f1d2..724c7c5d0142 100644
--- a/tests/pure/esnext.iterator.some.js
+++ b/tests/pure/esnext.iterator.some.js
@@ -12,10 +12,11 @@ QUnit.test('Iterator#some', assert => {
 
   assert.true(some.call(createIterator([1, 2, 3]), it => it % 2), 'basic functionality #1');
   assert.false(some.call(createIterator([1, 2, 3]), it => typeof it == 'string'), 'basic functionality #2');
-  some.call(createIterator([1]), function (arg) {
+  some.call(createIterator([1]), function (arg, counter) {
     assert.same(this, STRICT_THIS, 'this');
-    assert.same(arguments.length, 1, 'arguments length');
+    assert.same(arguments.length, 2, 'arguments length');
     assert.same(arg, 1, 'argument');
+    assert.same(counter, 0, 'counter');
   });
 
   assert.throws(() => some.call(undefined, () => { /* empty */ }), TypeError);
diff --git a/tests/tests/esnext.iterator.every.js b/tests/tests/esnext.iterator.every.js
index f65b566c4e05..2c9a790754ce 100644
--- a/tests/tests/esnext.iterator.every.js
+++ b/tests/tests/esnext.iterator.every.js
@@ -12,10 +12,11 @@ QUnit.test('Iterator#every', assert => {
 
   assert.true(every.call(createIterator([1, 2, 3]), it => typeof it == 'number'), 'basic functionality #1');
   assert.false(every.call(createIterator([1, 2, 3]), it => it % 2), 'basic functionality #2');
-  every.call(createIterator([1]), function (arg) {
+  every.call(createIterator([1]), function (arg, counter) {
     assert.same(this, STRICT_THIS, 'this');
-    assert.same(arguments.length, 1, 'arguments length');
+    assert.same(arguments.length, 2, 'arguments length');
     assert.same(arg, 1, 'argument');
+    assert.same(counter, 0, 'counter');
   });
 
   assert.throws(() => every.call(undefined, () => { /* empty */ }), TypeError);
diff --git a/tests/tests/esnext.iterator.filter.js b/tests/tests/esnext.iterator.filter.js
index 5e2fcb5e8a70..ca38448a469f 100644
--- a/tests/tests/esnext.iterator.filter.js
+++ b/tests/tests/esnext.iterator.filter.js
@@ -11,10 +11,11 @@ QUnit.test('Iterator#filter', assert => {
   assert.nonEnumerable(Iterator.prototype, 'filter');
 
   assert.arrayEqual(filter.call(createIterator([1, 2, 3]), it => it % 2).toArray(), [1, 3], 'basic functionality');
-  filter.call(createIterator([1]), function (arg) {
+  filter.call(createIterator([1]), function (arg, counter) {
     assert.same(this, STRICT_THIS, 'this');
-    assert.same(arguments.length, 1, 'arguments length');
+    assert.same(arguments.length, 2, 'arguments length');
     assert.same(arg, 1, 'argument');
+    assert.same(counter, 0, 'counter');
   });
 
   assert.throws(() => filter.call(undefined, () => { /* empty */ }), TypeError);
diff --git a/tests/tests/esnext.iterator.find.js b/tests/tests/esnext.iterator.find.js
index 65522b28cb99..42dcced0483d 100644
--- a/tests/tests/esnext.iterator.find.js
+++ b/tests/tests/esnext.iterator.find.js
@@ -11,10 +11,11 @@ QUnit.test('Iterator#find', assert => {
   assert.nonEnumerable(Iterator.prototype, 'find');
 
   assert.same(find.call(createIterator([1, 2, 3]), it => !(it % 2)), 2, 'basic functionality');
-  find.call(createIterator([1]), function (arg) {
+  find.call(createIterator([1]), function (arg, counter) {
     assert.same(this, STRICT_THIS, 'this');
-    assert.same(arguments.length, 1, 'arguments length');
+    assert.same(arguments.length, 2, 'arguments length');
     assert.same(arg, 1, 'argument');
+    assert.same(counter, 0, 'counter');
   });
 
   assert.throws(() => find.call(undefined, () => { /* empty */ }), TypeError);
diff --git a/tests/tests/esnext.iterator.flat-map.js b/tests/tests/esnext.iterator.flat-map.js
index 0b982623af2c..295d3c02d603 100644
--- a/tests/tests/esnext.iterator.flat-map.js
+++ b/tests/tests/esnext.iterator.flat-map.js
@@ -15,10 +15,11 @@ QUnit.test('Iterator#flatMap', assert => {
     [-1, -2, 3, 4, 5, 6, 'a', 'b'],
     'basic functionality',
   );
-  flatMap.call(createIterator([1]), function (arg) {
+  flatMap.call(createIterator([1]), function (arg, counter) {
     assert.same(this, STRICT_THIS, 'this');
-    assert.same(arguments.length, 1, 'arguments length');
+    assert.same(arguments.length, 2, 'arguments length');
     assert.same(arg, 1, 'argument');
+    assert.same(counter, 0, 'counter');
     return [arg];
   }).toArray();
 
diff --git a/tests/tests/esnext.iterator.for-each.js b/tests/tests/esnext.iterator.for-each.js
index 8f1905da12ae..546a9a519d94 100644
--- a/tests/tests/esnext.iterator.for-each.js
+++ b/tests/tests/esnext.iterator.for-each.js
@@ -16,10 +16,11 @@ QUnit.test('Iterator#forEach', assert => {
 
   assert.arrayEqual(array, [1, 2, 3], 'basic functionality');
 
-  forEach.call(createIterator([1]), function (arg) {
+  forEach.call(createIterator([1]), function (arg, counter) {
     assert.same(this, STRICT_THIS, 'this');
-    assert.same(arguments.length, 1, 'arguments length');
+    assert.same(arguments.length, 2, 'arguments length');
     assert.same(arg, 1, 'argument');
+    assert.same(counter, 0, 'counter');
   });
 
   assert.throws(() => forEach.call(undefined, () => { /* empty */ }), TypeError);
diff --git a/tests/tests/esnext.iterator.map.js b/tests/tests/esnext.iterator.map.js
index b63542f4a366..da912c5b889f 100644
--- a/tests/tests/esnext.iterator.map.js
+++ b/tests/tests/esnext.iterator.map.js
@@ -11,10 +11,11 @@ QUnit.test('Iterator#map', assert => {
   assert.nonEnumerable(Iterator.prototype, 'map');
 
   assert.arrayEqual(map.call(createIterator([1, 2, 3]), it => it ** 2).toArray(), [1, 4, 9], 'basic functionality');
-  map.call(createIterator([1]), function (arg) {
+  map.call(createIterator([1]), function (arg, counter) {
     assert.same(this, STRICT_THIS, 'this');
-    assert.same(arguments.length, 1, 'arguments length');
+    assert.same(arguments.length, 2, 'arguments length');
     assert.same(arg, 1, 'argument');
+    assert.same(counter, 0, 'counter');
   }).toArray();
 
   assert.throws(() => map.call(undefined, () => { /* empty */ }), TypeError);
diff --git a/tests/tests/esnext.iterator.reduce.js b/tests/tests/esnext.iterator.reduce.js
index b423232fcf4d..bf66794d66b9 100644
--- a/tests/tests/esnext.iterator.reduce.js
+++ b/tests/tests/esnext.iterator.reduce.js
@@ -12,11 +12,12 @@ QUnit.test('Iterator#reduce', assert => {
 
   assert.same(reduce.call(createIterator([1, 2, 3]), (a, b) => a + b, 1), 7, 'basic functionality');
   assert.same(reduce.call(createIterator([1, 2, 3]), (a, b) => a + b), 6, 'basic functionality, no init');
-  reduce.call(createIterator([2]), function (a, b) {
+  reduce.call(createIterator([2]), function (a, b, counter) {
     assert.same(this, STRICT_THIS, 'this');
-    assert.same(arguments.length, 2, 'arguments length');
+    assert.same(arguments.length, 3, 'arguments length');
     assert.same(a, 1, 'argument 1');
     assert.same(b, 2, 'argument 2');
+    assert.same(counter, 0, 'counter');
   }, 1);
 
   assert.throws(() => reduce.call(undefined, (a, b) => a + b, 0), TypeError);
diff --git a/tests/tests/esnext.iterator.some.js b/tests/tests/esnext.iterator.some.js
index 749fe6b39946..3d9ecc9e3623 100644
--- a/tests/tests/esnext.iterator.some.js
+++ b/tests/tests/esnext.iterator.some.js
@@ -12,10 +12,11 @@ QUnit.test('Iterator#some', assert => {
 
   assert.true(some.call(createIterator([1, 2, 3]), it => it % 2), 'basic functionality #1');
   assert.false(some.call(createIterator([1, 2, 3]), it => typeof it == 'string'), 'basic functionality #2');
-  some.call(createIterator([1]), function (arg) {
+  some.call(createIterator([1]), function (arg, counter) {
     assert.same(this, STRICT_THIS, 'this');
-    assert.same(arguments.length, 1, 'arguments length');
+    assert.same(arguments.length, 2, 'arguments length');
     assert.same(arg, 1, 'argument');
+    assert.same(counter, 0, 'counter');
   });
 
   assert.throws(() => some.call(undefined, () => { /* empty */ }), TypeError);