diff --git a/CHANGELOG.md b/CHANGELOG.md
index cd9cd23e47..98822371cb 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -14,6 +14,7 @@
 
 #### :rocket: New Feature
 
+- Add `Dict.has` and double `Dict.forEachWithKey`/`Dict.mapValues` performance. https://github.com/rescript-lang/rescript/pull/7316
 - Add popover attributes to JsxDOM.domProps. https://github.com/rescript-lang/rescript/pull/7317
 
 #### :house: Internal
diff --git a/lib/es6/Stdlib_Dict.js b/lib/es6/Stdlib_Dict.js
index 4d12162214..9a472ed5c4 100644
--- a/lib/es6/Stdlib_Dict.js
+++ b/lib/es6/Stdlib_Dict.js
@@ -10,21 +10,25 @@ function forEach(dict, f) {
 }
 
 function forEachWithKey(dict, f) {
-  Object.entries(dict).forEach(param => f(param[1], param[0]));
+  Object.keys(dict).forEach(key => f(dict[key], key));
 }
 
 function mapValues(dict, f) {
   let target = {};
-  forEachWithKey(dict, (value, key) => {
+  Object.keys(dict).forEach(key => {
+    let value = dict[key];
     target[key] = f(value);
   });
   return target;
 }
 
+let has = ((dict, key) => key in dict);
+
 export {
   $$delete$1 as $$delete,
   forEach,
   forEachWithKey,
   mapValues,
+  has,
 }
 /* No side effect */
diff --git a/lib/js/Stdlib_Dict.js b/lib/js/Stdlib_Dict.js
index 4e8aab1fe0..28788f4ec1 100644
--- a/lib/js/Stdlib_Dict.js
+++ b/lib/js/Stdlib_Dict.js
@@ -10,19 +10,23 @@ function forEach(dict, f) {
 }
 
 function forEachWithKey(dict, f) {
-  Object.entries(dict).forEach(param => f(param[1], param[0]));
+  Object.keys(dict).forEach(key => f(dict[key], key));
 }
 
 function mapValues(dict, f) {
   let target = {};
-  forEachWithKey(dict, (value, key) => {
+  Object.keys(dict).forEach(key => {
+    let value = dict[key];
     target[key] = f(value);
   });
   return target;
 }
 
+let has = ((dict, key) => key in dict);
+
 exports.$$delete = $$delete$1;
 exports.forEach = forEach;
 exports.forEachWithKey = forEachWithKey;
 exports.mapValues = mapValues;
+exports.has = has;
 /* No side effect */
diff --git a/runtime/Stdlib_Dict.res b/runtime/Stdlib_Dict.res
index 0c5b82372f..7393c4fb61 100644
--- a/runtime/Stdlib_Dict.res
+++ b/runtime/Stdlib_Dict.res
@@ -28,8 +28,9 @@ let forEach = (dict, f) => {
   dict->valuesToArray->Stdlib_Array.forEach(value => f(value))
 }
 
+@inline
 let forEachWithKey = (dict, f) => {
-  dict->toArray->Stdlib_Array.forEach(((key, value)) => f(value, key))
+  dict->keysToArray->Stdlib_Array.forEach(key => f(dict->getUnsafe(key), key))
 }
 
 let mapValues = (dict, f) => {
@@ -39,3 +40,5 @@ let mapValues = (dict, f) => {
   })
   target
 }
+
+let has: (dict<'a>, string) => bool = %raw(`(dict, key) => key in dict`)
diff --git a/runtime/Stdlib_Dict.resi b/runtime/Stdlib_Dict.resi
index 94b5c14d52..64f3c175dc 100644
--- a/runtime/Stdlib_Dict.resi
+++ b/runtime/Stdlib_Dict.resi
@@ -17,7 +17,7 @@ Use `Dict.getUnsafe` only when you are sure the key exists (i.e. when iterating
 
 ## Examples
 ```rescript
-let dict = Dict.fromArray([("key1", "value1"), ("key2", "value2")])
+let dict = dict{"key1": "value1", "key2": "value2"}
 let value = dict->Dict.getUnsafe("key1")
 Console.log(value) // value1
 ```
@@ -30,7 +30,7 @@ Returns the value at the provided key, if it exists. Returns an option.
 
 ## Examples
 ```rescript
-let dict = Dict.fromArray([("someKey", "someValue")])
+let dict = dict{"someKey": "someValue"}
 
 switch dict->Dict.get("someKey") {
 | None => Console.log("Nope, didn't have the key.")
@@ -59,7 +59,7 @@ external set: (dict<'a>, string, 'a) => unit = ""
 
 ## Examples
 ```rescript
-let dict = Dict.fromArray([("someKey", "someValue")])
+let dict = dict{"someKey": "someValue"}
 
 dict->Dict.delete("someKey")
 ```
@@ -189,7 +189,7 @@ external assign: (dict<'a>, dict<'a>) => dict<'a> = "Object.assign"
 
 ## Examples
 ```rescript
-let dict = Dict.fromArray([("key1", "value1"), ("key2", "value2")])
+let dict = dict{"key1": "value1", "key2": "value2"}
 let dict2 = dict->Dict.copy
 
 // Both log `["key1", "key2"]` here.
@@ -206,7 +206,7 @@ external copy: (@as(json`{}`) _, dict<'a>) => dict<'a> = "Object.assign"
 
 ## Examples
 ```rescript
-let dict = Dict.fromArray([("key1", "value1"), ("key2", "value2")])
+let dict = dict{"key1": "value1", "key2": "value2"}
 
 dict->Dict.forEach(value => {
   Console.log(value)
@@ -220,7 +220,7 @@ let forEach: (dict<'a>, 'a => unit) => unit
 
 ## Examples
 ```rescript
-let dict = Dict.fromArray([("key1", "value1"), ("key2", "value2")])
+let dict = dict{"key1": "value1", "key2": "value2"}
 
 dict->Dict.forEachWithKey((value, key) => {
   Console.log2(value, key)
@@ -235,10 +235,25 @@ let forEachWithKey: (dict<'a>, ('a, string) => unit) => unit
 ## Examples
 
 ```rescript
-let dict = Dict.fromArray([("key1", 1), ("key2", 2)])
+let dict = dict{"key1": 1, "key2": 2}
 
 dict->Dict.mapValues(v => v + 10)->Dict.toArray // [("key1", 11), ("key2", 12)]
 dict->Dict.mapValues(v => Int.toString(v))->Dict.toArray // [("key1", "1"), ("key2", "2")]
 ```
 */
 let mapValues: (dict<'a>, 'a => 'b) => dict<'b>
+
+/**
+`has(dictionary, "key")` returns true if the "key" is present in the dictionary.
+
+## Examples
+
+```rescript
+let dict = dict{"key1": Some(1), "key2": None}
+
+dict->Dict.has("key1") // true
+dict->Dict.has("key2") // true
+dict->Dict.has("key3") // false
+```
+*/
+let has: (dict<'a>, string) => bool
diff --git a/tests/tests/src/DictTests.mjs b/tests/tests/src/DictTests.mjs
index a1a763250b..b57778e88f 100644
--- a/tests/tests/src/DictTests.mjs
+++ b/tests/tests/src/DictTests.mjs
@@ -1,5 +1,6 @@
 // Generated by ReScript, PLEASE EDIT WITH CARE
 
+import * as Stdlib_Dict from "rescript/lib/es6/Stdlib_Dict.js";
 
 let someString = "hello";
 
@@ -41,6 +42,51 @@ let PatternMatching = {
   constrainedAsDict: constrainedAsDict
 };
 
+let dict = {
+  key1: 1,
+  key2: undefined
+};
+
+if (Stdlib_Dict.has(dict, "key1") !== true) {
+  throw {
+    RE_EXN_ID: "Assert_failure",
+    _1: [
+      "DictTests.res",
+      43,
+      2
+    ],
+    Error: new Error()
+  };
+}
+
+if (Stdlib_Dict.has(dict, "key2") !== true) {
+  throw {
+    RE_EXN_ID: "Assert_failure",
+    _1: [
+      "DictTests.res",
+      44,
+      2
+    ],
+    Error: new Error()
+  };
+}
+
+if (Stdlib_Dict.has(dict, "key3") !== false) {
+  throw {
+    RE_EXN_ID: "Assert_failure",
+    _1: [
+      "DictTests.res",
+      45,
+      2
+    ],
+    Error: new Error()
+  };
+}
+
+let DictHas = {
+  dict: dict
+};
+
 let three = 3;
 
 export {
@@ -49,5 +95,6 @@ export {
   three,
   intDict,
   PatternMatching,
+  DictHas,
 }
-/* No side effect */
+/*  Not a pure module */
diff --git a/tests/tests/src/DictTests.res b/tests/tests/src/DictTests.res
index e1d2523cac..feb62ade9f 100644
--- a/tests/tests/src/DictTests.res
+++ b/tests/tests/src/DictTests.res
@@ -33,3 +33,14 @@ module PatternMatching = {
     | _ => Js.log("not one")
     }
 }
+
+module DictHas = {
+  let dict = dict{
+    "key1": Some(1),
+    "key2": None,
+  }
+
+  assert(dict->Dict.has("key1") === true)
+  assert(dict->Dict.has("key2") === true)
+  assert(dict->Dict.has("key3") === false)
+}