diff --git a/Interop/Runtime/build.gradle b/Interop/Runtime/build.gradle
index a5735ddd592..d2b94ee2e63 100644
--- a/Interop/Runtime/build.gradle
+++ b/Interop/Runtime/build.gradle
@@ -74,7 +74,7 @@ sourceSets.main.kotlin.srcDirs += "src/jvm/kotlin"
 
 compileKotlin {
     kotlinOptions {
-        freeCompilerArgs = ['-Xuse-experimental=kotlin.ExperimentalUnsignedTypes', "-XXLanguage:+InlineClasses"]
+        freeCompilerArgs = ['-Xopt-in=kotlin.ExperimentalUnsignedTypes', '-Xinline-classes']
     }
 }
 
diff --git a/Interop/Runtime/src/main/kotlin/kotlinx/cinterop/Utils.kt b/Interop/Runtime/src/main/kotlin/kotlinx/cinterop/Utils.kt
index 3062fd3fd68..c85f8e9090e 100644
--- a/Interop/Runtime/src/main/kotlin/kotlinx/cinterop/Utils.kt
+++ b/Interop/Runtime/src/main/kotlin/kotlinx/cinterop/Utils.kt
@@ -560,7 +560,7 @@ public fun CPointer<IntVar>.toKStringFromUtf32(): String {
  *
  * Malformed byte sequences are replaced by the replacement char `\uFFFD`.
  */
-@UseExperimental(ExperimentalStdlibApi::class)
+@OptIn(ExperimentalStdlibApi::class)
 @SinceKotlin("1.3")
 public fun ByteArray.toKString() : String {
     val realEndIndex = realEndIndex(this, 0, this.size)
@@ -579,7 +579,7 @@ public fun ByteArray.toKString() : String {
  * @throws IllegalArgumentException if [startIndex] is greater than [endIndex].
  * @throws CharacterCodingException if the byte array contains malformed UTF-8 byte sequence and [throwOnInvalidSequence] is true.
  */
-@UseExperimental(ExperimentalStdlibApi::class)
+@OptIn(ExperimentalStdlibApi::class)
 @SinceKotlin("1.3")
 public fun ByteArray.toKString(
         startIndex: Int = 0,
diff --git a/Interop/StubGenerator/build.gradle b/Interop/StubGenerator/build.gradle
index 1624b3e7363..aa5dc0151a8 100644
--- a/Interop/StubGenerator/build.gradle
+++ b/Interop/StubGenerator/build.gradle
@@ -44,6 +44,6 @@ dependencies {
 
 compileKotlin {
     kotlinOptions {
-        freeCompilerArgs = ['-Xuse-experimental=kotlin.ExperimentalUnsignedTypes', '-Xskip-metadata-version-check']
+        freeCompilerArgs = ['-Xopt-in=kotlin.ExperimentalUnsignedTypes', '-Xskip-metadata-version-check']
     }
 }
diff --git a/backend.native/build.gradle b/backend.native/build.gradle
index 8481d3d9841..a441d21bacd 100644
--- a/backend.native/build.gradle
+++ b/backend.native/build.gradle
@@ -219,9 +219,9 @@ targetList.each { target ->
         args = [*konanArgs,
                 '-output', project(':runtime').file("build/${target}Stdlib"),
                 '-produce', 'library', '-module-name', 'stdlib', '-XXLanguage:+AllowContractsForCustomFunctions',
-                '-Xmulti-platform', '-Xuse-experimental=kotlin.Experimental', '-XXLanguage:+InlineClasses',
-                '-Xuse-experimental=kotlin.contracts.ExperimentalContracts',
-                '-Xuse-experimental=kotlin.ExperimentalMultiplatform',
+                '-Xmulti-platform', '-Xopt-in=kotlin.RequiresOptIn', '-Xinline-classes',
+                '-Xopt-in=kotlin.contracts.ExperimentalContracts',
+                '-Xopt-in=kotlin.ExperimentalMultiplatform',
                 '-Xallow-result-return-type',
                 commonSrc.absolutePath,
                 "-Xcommon-sources=${commonSrc.absolutePath}",
diff --git a/backend.native/tests/build.gradle b/backend.native/tests/build.gradle
index 0bbc8f65f29..4e340b907f7 100644
--- a/backend.native/tests/build.gradle
+++ b/backend.native/tests/build.gradle
@@ -1446,7 +1446,7 @@ linkTest("classDelegation_linkTest") {
 }
 
 standaloneTest("contracts") {
-    flags = [ '-Xuse-experimental=kotlin.Experimental', '-tr' ]
+    flags = [ '-Xopt-in=kotlin.RequiresOptIn', '-tr' ]
     source = "codegen/contracts/contracts.kt"
 }
 
@@ -4180,7 +4180,7 @@ KotlinNativeTestKt.createTest(project, 'stdlibTest', KonanGTest) { task ->
             baseDir "$testOutputStdlib/stdlibTest"
             enableMultiplatform true
             extraOpts '-tr',
-                    '-Xuse-experimental=kotlin.Experimental,kotlin.ExperimentalStdlibApi',
+                    '-Xopt-in=kotlin.RequiresOptIn,kotlin.ExperimentalStdlibApi',
                     "-friend-modules", project.rootProject.file("${project.properties['konan.home']}/klib/common/stdlib").absolutePath
             extraOpts project.globalTestArgs
         }
diff --git a/backend.native/tests/codegen/associatedObjects/associatedObjects1.kt b/backend.native/tests/codegen/associatedObjects/associatedObjects1.kt
index a239b8ba0fa..02f1862655f 100644
--- a/backend.native/tests/codegen/associatedObjects/associatedObjects1.kt
+++ b/backend.native/tests/codegen/associatedObjects/associatedObjects1.kt
@@ -9,7 +9,7 @@ import kotlin.test.*
 import kotlin.reflect.*
 
 @Test
-@UseExperimental(ExperimentalAssociatedObjects::class)
+@OptIn(ExperimentalAssociatedObjects::class)
 fun testBasics1() {
     assertSame(Bar, Foo::class.findAssociatedObject<Associated1>())
     assertSame(Baz, Foo::class.findAssociatedObject<Associated2>())
@@ -18,17 +18,17 @@ fun testBasics1() {
     assertSame(null, Bar::class.findAssociatedObject<Associated1>())
 }
 
-@UseExperimental(ExperimentalAssociatedObjects::class)
+@OptIn(ExperimentalAssociatedObjects::class)
 @AssociatedObjectKey
 @Retention(AnnotationRetention.BINARY)
 annotation class Associated1(val kClass: KClass<*>)
 
-@UseExperimental(ExperimentalAssociatedObjects::class)
+@OptIn(ExperimentalAssociatedObjects::class)
 @AssociatedObjectKey
 @Retention(AnnotationRetention.BINARY)
 annotation class Associated2(val kClass: KClass<*>)
 
-@UseExperimental(ExperimentalAssociatedObjects::class)
+@OptIn(ExperimentalAssociatedObjects::class)
 @AssociatedObjectKey
 @Retention(AnnotationRetention.BINARY)
 annotation class Associated3(val kClass: KClass<*>)
@@ -41,7 +41,7 @@ object Bar
 object Baz
 
 @Test
-@UseExperimental(ExperimentalAssociatedObjects::class)
+@OptIn(ExperimentalAssociatedObjects::class)
 fun testGlobalOptimizations1() {
     val i1 = I1ImplHolder::class.findAssociatedObject<Associated1>()!! as I1
     assertEquals(42, i1.foo())
@@ -68,7 +68,7 @@ private object I1Impl : I1 {
 private class I1ImplHolder
 
 @Test
-@UseExperimental(ExperimentalAssociatedObjects::class)
+@OptIn(ExperimentalAssociatedObjects::class)
 fun testGlobalOptimizations2() {
     val i2 = I2ImplHolder()::class.findAssociatedObject<Associated1>()!! as I2
     assertEquals(17, i2.foo())
diff --git a/backend.native/tests/codegen/contracts/contracts.kt b/backend.native/tests/codegen/contracts/contracts.kt
index f9ab1154b44..cf87b973605 100644
--- a/backend.native/tests/codegen/contracts/contracts.kt
+++ b/backend.native/tests/codegen/contracts/contracts.kt
@@ -4,7 +4,7 @@ import kotlin.contracts.*
 open class S
 class P(val str: String = "P") : S()
 
-@UseExperimental(kotlin.contracts.ExperimentalContracts::class)
+@OptIn(kotlin.contracts.ExperimentalContracts::class)
 fun check(actual: Boolean) {
     contract { returns() implies actual }
     assertTrue(actual)
diff --git a/backend.native/tests/codegen/ktype/ktype1.kt b/backend.native/tests/codegen/ktype/ktype1.kt
index b6e66034816..c5649433f82 100644
--- a/backend.native/tests/codegen/ktype/ktype1.kt
+++ b/backend.native/tests/codegen/ktype/ktype1.kt
@@ -8,7 +8,7 @@ package codegen.ktype.ktype1
 import kotlin.test.*
 import kotlin.reflect.*
 
-@UseExperimental(ExperimentalStdlibApi::class)
+@OptIn(ExperimentalStdlibApi::class)
 inline fun <reified R> kType() = typeOf<R>()
 
 inline fun <reified R> kType(obj: R) = kType<R>()
diff --git a/build-tools/src/main/groovy/org/jetbrains/kotlin/KonanTest.groovy b/build-tools/src/main/groovy/org/jetbrains/kotlin/KonanTest.groovy
index d50c450a81f..4f4ffb739df 100644
--- a/build-tools/src/main/groovy/org/jetbrains/kotlin/KonanTest.groovy
+++ b/build-tools/src/main/groovy/org/jetbrains/kotlin/KonanTest.groovy
@@ -332,7 +332,7 @@ class RunExternalTestGroup extends OldKonanTest {
         def experimentalSettings = findLinesWithPrefixesRemoved(text, "// !USE_EXPERIMENTAL: ")
         if (experimentalSettings.size() != 0) {
             experimentalSettings.forEach { line ->
-                line.split(" ").toList().forEach { flags.add("-Xuse-experimental=$it") }
+                line.split(" ").toList().forEach { flags.add("-Xopt-in=$it") }
             }
         }
     }
diff --git a/endorsedLibraries/kotlinx.cli/build.gradle b/endorsedLibraries/kotlinx.cli/build.gradle
index 65d8c4cf074..478c1c4d540 100644
--- a/endorsedLibraries/kotlinx.cli/build.gradle
+++ b/endorsedLibraries/kotlinx.cli/build.gradle
@@ -60,7 +60,7 @@ kotlin {
 
         jvm().compilations.all {
             kotlinOptions {
-                freeCompilerArgs = ["-Xuse-experimental=kotlinx.cli.ExperimentalCli"]
+                freeCompilerArgs = ["-Xopt-in=kotlinx.cli.ExperimentalCli"]
                 suppressWarnings = true
             }
         }
@@ -92,8 +92,8 @@ targetList.each { target ->
         args = [*konanArgs,
                 '-output', project.file("build/${target}KotlinxCli"),
                 '-produce', 'library', '-module-name', 'kotlinx-cli', '-XXLanguage:+AllowContractsForCustomFunctions',
-                '-Xmulti-platform', '-Xuse-experimental=kotlinx.cli.ExperimentalCli',
-                '-Xuse-experimental=kotlin.ExperimentalMultiplatform',
+                '-Xmulti-platform', '-Xopt-in=kotlinx.cli.ExperimentalCli',
+                '-Xopt-in=kotlin.ExperimentalMultiplatform',
                 '-Xallow-result-return-type',
                 commonSrc.absolutePath,
                 "-Xcommon-sources=${commonSrc.absolutePath}",
diff --git a/performance/shared/src/main/kotlin/org/jetbrains/benchmarksLauncher/launcher.kt b/performance/shared/src/main/kotlin/org/jetbrains/benchmarksLauncher/launcher.kt
index 1ffbf0918f0..60526df130f 100644
--- a/performance/shared/src/main/kotlin/org/jetbrains/benchmarksLauncher/launcher.kt
+++ b/performance/shared/src/main/kotlin/org/jetbrains/benchmarksLauncher/launcher.kt
@@ -13,7 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-@file:UseExperimental(ExperimentalCli::class)
+@file:OptIn(ExperimentalCli::class)
 package org.jetbrains.benchmarksLauncher
 
 import org.jetbrains.report.BenchmarkResult
diff --git a/runtime/src/main/kotlin/kotlin/collections/Arrays.kt b/runtime/src/main/kotlin/kotlin/collections/Arrays.kt
index 6768b62d610..9e206f9f250 100644
--- a/runtime/src/main/kotlin/kotlin/collections/Arrays.kt
+++ b/runtime/src/main/kotlin/kotlin/collections/Arrays.kt
@@ -45,7 +45,7 @@ public inline fun <T> Array<out T>.subarrayContentToString(offset: Int, length:
  * If any of arrays contains itself on any nesting level the behavior is undefined.
  */
 @SinceKotlin("1.1")
-@UseExperimental(ExperimentalUnsignedTypes::class)
+@OptIn(ExperimentalUnsignedTypes::class)
 internal fun <T> Array<out T>?.contentDeepHashCodeImpl(): Int {
     if (this == null) return 0
     var result = 1
diff --git a/runtime/src/main/kotlin/kotlin/collections/HashMap.kt b/runtime/src/main/kotlin/kotlin/collections/HashMap.kt
index 7c982e0c464..a8a07d23590 100644
--- a/runtime/src/main/kotlin/kotlin/collections/HashMap.kt
+++ b/runtime/src/main/kotlin/kotlin/collections/HashMap.kt
@@ -512,10 +512,10 @@ actual class HashMap<K, V> private constructor(
         const val INITIAL_MAX_PROBE_DISTANCE = 2
         const val TOMBSTONE = -1
 
-        @UseExperimental(ExperimentalStdlibApi::class)
+        @OptIn(ExperimentalStdlibApi::class)
         fun computeHashSize(capacity: Int): Int = (capacity.coerceAtLeast(1) * 3).takeHighestOneBit()
 
-        @UseExperimental(ExperimentalStdlibApi::class)
+        @OptIn(ExperimentalStdlibApi::class)
         fun computeShift(hashSize: Int): Int = hashSize.countLeadingZeroBits() + 1
     }
 
diff --git a/runtime/src/main/kotlin/kotlin/reflect/AssociatedObjects.kt b/runtime/src/main/kotlin/kotlin/reflect/AssociatedObjects.kt
index 1e3102a1d06..7a2af7efd65 100644
--- a/runtime/src/main/kotlin/kotlin/reflect/AssociatedObjects.kt
+++ b/runtime/src/main/kotlin/kotlin/reflect/AssociatedObjects.kt
@@ -11,10 +11,10 @@ import kotlin.native.internal.*
  * The experimental marker for associated objects API.
  *
  * Any usage of a declaration annotated with `@ExperimentalAssociatedObjects` must be accepted either by
- * annotating that usage with the [UseExperimental] annotation, e.g. `@UseExperimental(ExperimentalAssociatedObjects::class)`,
- * or by using the compiler argument `-Xuse-experimental=kotlin.reflect.ExperimentalAssociatedObjects`.
+ * annotating that usage with the [OptIn] annotation, e.g. `@OptIn(ExperimentalAssociatedObjects::class)`,
+ * or by using the compiler argument `-Xopt-in=kotlin.reflect.ExperimentalAssociatedObjects`.
  */
-@Experimental(level = Experimental.Level.ERROR)
+@RequiresOptIn(level = RequiresOptIn.Level.ERROR)
 @Retention(value = AnnotationRetention.BINARY)
 public annotation class ExperimentalAssociatedObjects
 
diff --git a/runtime/src/main/kotlin/kotlin/text/StringBuilder.kt b/runtime/src/main/kotlin/kotlin/text/StringBuilder.kt
index c3f509e673e..2bb953fd712 100644
--- a/runtime/src/main/kotlin/kotlin/text/StringBuilder.kt
+++ b/runtime/src/main/kotlin/kotlin/text/StringBuilder.kt
@@ -58,7 +58,7 @@ actual class StringBuilder private constructor (
         return append(toAppend, 0, toAppend.length)
     }
 
-    @UseExperimental(ExperimentalStdlibApi::class)
+    @OptIn(ExperimentalStdlibApi::class)
     actual override fun append(value: CharSequence?, startIndex: Int, endIndex: Int): StringBuilder = this.appendRange(value, startIndex, endIndex)
 
     /**
@@ -319,7 +319,7 @@ actual class StringBuilder private constructor (
      *
      * @throws IndexOutOfBoundsException if [index] is less than zero or greater than the length of this string builder.
      */
-    @UseExperimental(ExperimentalStdlibApi::class)
+    @OptIn(ExperimentalStdlibApi::class)
     actual fun insert(index: Int, value: CharSequence?): StringBuilder {
         // Kotlin/JVM inserts the "null" string if the argument is null.
         val toInsert = value ?: "null"
@@ -887,7 +887,7 @@ public inline fun StringBuilder.setLength(l: Int) = this.setLength(newLength = l
  * @throws IndexOutOfBoundsException or [IllegalArgumentException] when [start] or [end] is out of range of the [csq] character sequence indices or when `start > end`.
  * @throws IndexOutOfBoundsException if [index] is less than zero or greater than the length of this string builder.
  */
-@UseExperimental(ExperimentalStdlibApi::class)
+@OptIn(ExperimentalStdlibApi::class)
 @kotlin.internal.InlineOnly
 public inline fun StringBuilder.insert(index: Int, csq: CharSequence?, start: Int, end: Int): StringBuilder =
         this.insertRange(index, csq, start, end)
@@ -905,6 +905,6 @@ public inline fun StringBuilder.setCharAt(index: Int, value: Char) = this.set(in
  *
  * @throws IndexOutOfBoundsException if [index] is out of bounds of this string builder.
  */
-@UseExperimental(ExperimentalStdlibApi::class)
+@OptIn(ExperimentalStdlibApi::class)
 @kotlin.internal.InlineOnly
 public inline fun StringBuilder.deleteCharAt(index: Int) = this.deleteAt(index)
diff --git a/runtime/src/main/kotlin/kotlin/text/regex/CharClass.kt b/runtime/src/main/kotlin/kotlin/text/regex/CharClass.kt
index fc4186e4adf..0915c5cf8a6 100644
--- a/runtime/src/main/kotlin/kotlin/text/regex/CharClass.kt
+++ b/runtime/src/main/kotlin/kotlin/text/regex/CharClass.kt
@@ -485,7 +485,7 @@ internal class CharClass(val ignoreCase: Boolean = false, negative: Boolean = fa
         }
     }
 
-    @UseExperimental(ExperimentalStdlibApi::class)
+    @OptIn(ExperimentalStdlibApi::class)
     override val instance: AbstractCharClass
         get() {
 
@@ -519,7 +519,7 @@ internal class CharClass(val ignoreCase: Boolean = false, negative: Boolean = fa
             }
         }
 
-    @UseExperimental(ExperimentalStdlibApi::class)
+    @OptIn(ExperimentalStdlibApi::class)
     //for debugging purposes only
     override fun toString(): String {
         val temp = StringBuilder()
diff --git a/tools/benchmarksAnalyzer/src/main/kotlin/main.kt b/tools/benchmarksAnalyzer/src/main/kotlin/main.kt
index b0f05949abb..7db7abfd088 100644
--- a/tools/benchmarksAnalyzer/src/main/kotlin/main.kt
+++ b/tools/benchmarksAnalyzer/src/main/kotlin/main.kt
@@ -13,7 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-@file:UseExperimental(ExperimentalCli::class)
+@file:OptIn(ExperimentalCli::class)
 import org.jetbrains.analyzer.sendGetRequest
 import org.jetbrains.analyzer.readFile
 import org.jetbrains.analyzer.SummaryBenchmarksReport