diff --git a/builtin/builtin.mbti b/builtin/builtin.mbti
index fb1231f23..2d84b452b 100644
--- a/builtin/builtin.mbti
+++ b/builtin/builtin.mbti
@@ -339,6 +339,11 @@ impl Map {
 }
 impl[K : Show, V : Show] Show for Map[K, V]
 
+pub(all) enum Mutability {
+  Mutable
+  Immutable
+}
+
 type Set
 impl Set {
   add[K : Hash + Eq](Self[K], K) -> Unit
@@ -792,6 +797,11 @@ impl Tuple(16) {
 // Type aliases
 
 // Traits
+pub(open) trait Clone {
+  mutability() -> Mutability
+  clone(Self) -> Self
+}
+
 pub(open) trait Compare : Eq {
   compare(Self, Self) -> Int
 }
diff --git a/builtin/clone.mbt b/builtin/clone.mbt
new file mode 100644
index 000000000..37b61bdaf
--- /dev/null
+++ b/builtin/clone.mbt
@@ -0,0 +1,261 @@
+// Copyright 2025 International Digital Economy Academy
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+///|
+impl Clone for Unit with mutability() { Immutable }
+
+///|
+impl Clone for Unit with clone(self) { self }
+
+///|
+impl Clone for Bool with mutability() { Immutable }
+
+///|
+impl Clone for Bool with clone(self) { self }
+
+///|
+impl Clone for Int with mutability() { Immutable }
+
+///|
+impl Clone for Int with clone(self) { self }
+
+///|
+impl Clone for Int64 with mutability() { Immutable }
+
+///|
+impl Clone for Int64 with clone(self) { self }
+
+///|
+impl Clone for UInt with mutability() { Immutable }
+
+///|
+impl Clone for UInt with clone(self) { self }
+
+///|
+impl Clone for Byte with mutability() { Immutable }
+
+///|
+impl Clone for Byte with clone(self) { self }
+
+///|
+impl Clone for String with mutability() { Immutable }
+
+///|
+impl Clone for String with clone(self) { self }
+
+// mutable containers
+
+///|
+fn copy_array[T](self : Array[T]) -> Array[T] {
+  let len = self.length()
+  if len == 0 {
+    []
+  } else {
+    let arr = Array::make(len, self[0])
+    Array::unsafe_blit(arr, 0, self, 0, len)
+    arr
+  }
+}
+
+///|
+impl[T : Clone] Clone for Array[T] with mutability() { Mutable }
+
+///|
+impl[T : Clone] Clone for Array[T] with clone(self) {
+  match T::mutability() {
+    Mutable => self.map(T::clone)
+    Immutable => self.copy_array()
+  }
+}
+
+test "Array[Int]::clone" {
+  let xs = [1, 2, 3, 4, 5]
+  let ys = xs.clone()
+  xs[0] = 99
+  inspect!(xs, content="[99, 2, 3, 4, 5]")
+  inspect!(ys, content="[1, 2, 3, 4, 5]")
+}
+
+test "Array[Ref[Int]]::clone" {
+  let xs = [1, 2, 3, 4, 5].map(fn(x) { { val: x } })
+  let ys = xs.clone()
+  xs[0].val = 99
+  inspect!(xs, content="[{val: 99}, {val: 2}, {val: 3}, {val: 4}, {val: 5}]")
+  inspect!(ys, content="[{val: 1}, {val: 2}, {val: 3}, {val: 4}, {val: 5}]")
+}
+
+///|
+impl[T : Clone] Clone for FixedArray[T] with mutability() { Mutable }
+
+///|
+fn map_fixedarray[T, U](self : FixedArray[T], f : (T) -> U) -> FixedArray[U] {
+  if self.length() == 0 {
+    return []
+  }
+  let res = FixedArray::make(self.length(), f(self[0]))
+  for i = 1; i < self.length(); i = i + 1 {
+    res[i] = f(self[i])
+  }
+  res
+}
+
+///|
+impl[T : Clone] Clone for FixedArray[T] with clone(self) {
+  match T::mutability() {
+    Mutable => self.map_fixedarray(T::clone)
+    Immutable => self.map_fixedarray(fn(x) { x })
+  }
+}
+
+test "FixedArray[Int]::clone" {
+  let xs : FixedArray[Int] = [1, 2, 3, 4, 5]
+  let ys = xs.clone()
+  xs[0] = 99
+  inspect!(xs, content="[99, 2, 3, 4, 5]")
+  inspect!(ys, content="[1, 2, 3, 4, 5]")
+}
+
+test "FixedArray[Ref[Int]]::clone" {
+  let xs = ([1, 2, 3, 4, 5] : FixedArray[Int]).map_fixedarray(fn(x) {
+    { val: x }
+  })
+  let ys = xs.clone()
+  xs[0].val = 99
+  inspect!(xs, content="[{val: 99}, {val: 2}, {val: 3}, {val: 4}, {val: 5}]")
+  inspect!(ys, content="[{val: 1}, {val: 2}, {val: 3}, {val: 4}, {val: 5}]")
+}
+
+///|
+impl[T : Clone] Clone for Ref[T] with mutability() { Mutable }
+
+///|
+impl[T : Clone] Clone for Ref[T] with clone(self) {
+  match T::mutability() {
+    Mutable => { val: T::clone(self.val) }
+    Immutable => { val: self.val }
+  }
+}
+
+test "Ref[Int]::clone" {
+  let x = { val: 0 }
+  let y = x.clone()
+  x.val = 10
+  inspect!(x, content="{val: 10}")
+  inspect!(y, content="{val: 0}")
+}
+
+///|
+impl Clone for Bytes with mutability() { Mutable }
+
+///|
+impl Clone for Bytes with clone(self) { self.copy() }
+
+test "Bytes::clone" {
+  let xs = b"\x12\x34"
+  let ys = xs.clone()
+  xs[0] = b'\x00'
+  let xss =
+    #|b"\x00\x34"
+  let yss =
+    #|b"\x12\x34"
+  inspect!(xs, content=xss)
+  inspect!(ys, content=yss)
+}
+
+// immutable containers
+
+///|
+impl[T : Clone] Clone for T? with mutability() { T::mutability() }
+
+///|
+impl[T : Clone] Clone for T? with clone(self) {
+  match T::mutability() {
+    Mutable =>
+      match self {
+        Some(x) => Some(T::clone(x))
+        None => None
+      }
+    Immutable => self
+  }
+}
+
+test "Ref[Int]?::clone" {
+  let x = Some({ val: 0 })
+  let y = x.clone()
+  x.unwrap().val = 99
+  inspect!(x, content="Some({val: 99})")
+  inspect!(y, content="Some({val: 0})")
+}
+
+///|
+impl[T : Clone, E : Clone] Clone for Result[T, E] with mutability() {
+  match (T::mutability(), E::mutability()) {
+    (Immutable, Immutable) => Immutable
+    _ => Mutable
+  }
+}
+
+///|
+impl[T : Clone, E : Clone] Clone for Result[T, E] with clone(self) {
+  match T::mutability() {
+    Mutable =>
+      match self {
+        Ok(x) => Ok(T::clone(x))
+        Err(x) => Err(E::clone(x))
+      }
+    Immutable => self
+  }
+}
+
+test "Result[Ref[Int],Ref[String]]::clone" {
+  let x : Result[Ref[Int], Ref[String]] = Ok({ val: 1 })
+  let y = x.clone()
+  match x {
+    Ok(x) => x.val = 99
+    Err(x) => x.val = "OvO"
+  }
+  inspect!(x, content="Ok({val: 99})")
+  inspect!(y, content="Ok({val: 1})")
+  let x : Result[Ref[Int], Ref[String]] = Err({ val: "mooncake" })
+  let y = x.clone()
+  match x {
+    Ok(x) => x.val = 99
+    Err(x) => x.val = "OvO"
+  }
+  inspect!(x, content="Err({val: \"OvO\"})")
+  inspect!(y, content="Err({val: \"mooncake\"})")
+}
+
+///|
+fn get_mutability[T : Clone](_ : T) -> Mutability {
+  T::mutability()
+}
+
+test "mutability" {
+
+  // immutable 
+  let oi = Some(0)
+  inspect!(get_mutability(oi), content="Immutable")
+  let ris : Result[Int, String] = Ok(32)
+  inspect!(get_mutability(ris), content="Immutable")
+  // TODO, we need to test reference equal
+
+  // mutable 
+  let ri : Ref[Int] = { val: 0 }
+  let ari = [ri]
+  let aoi = [oi]
+  inspect!(get_mutability(ri), content="Mutable")
+  inspect!(get_mutability(ari), content="Mutable")
+  inspect!(get_mutability(aoi), content="Mutable")
+}
diff --git a/builtin/traits.mbt b/builtin/traits.mbt
index 1fdaeec50..e145408c2 100644
--- a/builtin/traits.mbt
+++ b/builtin/traits.mbt
@@ -1,4 +1,4 @@
-// Copyright 2024 International Digital Economy Academy
+// Copyright 2025 International Digital Economy Academy
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -123,3 +123,15 @@ pub fn &Logger::write_iter[T : Show](
   self.write_string(suffix)
 }
 // TODO: Logger::write_double(self:Logger, val:Double) -> Unit
+
+///| 
+pub(all) enum Mutability {
+  Mutable
+  Immutable
+} derive(Show)
+
+///| Use clone method intended for cloned object's internal state won't be influenced original object
+pub(open) trait Clone {
+  mutability() -> Mutability
+  clone(Self) -> Self
+}