diff --git a/build.gradle b/build.gradle
index 60b7e2733..f696639fc 100644
--- a/build.gradle
+++ b/build.gradle
@@ -20,8 +20,7 @@ buildscript {
     ext.experimentalsInTestEnabled = ["-progressive", "-opt-in=kotlin.Experimental",
                                       "-opt-in=kotlin.ExperimentalMultiplatform",
                                       "-opt-in=kotlinx.serialization.ExperimentalSerializationApi",
-                                      "-opt-in=kotlinx.serialization.InternalSerializationApi",
-                                      "-opt-in=kotlin.ExperimentalUnsignedTypes"
+                                      "-opt-in=kotlinx.serialization.InternalSerializationApi"
     ]
     ext.koverEnabled = property('kover.enabled') ?: true
 
diff --git a/core/commonMain/src/kotlinx/serialization/builtins/BuiltinSerializers.kt b/core/commonMain/src/kotlinx/serialization/builtins/BuiltinSerializers.kt
index 91052fe2c..19698c459 100644
--- a/core/commonMain/src/kotlinx/serialization/builtins/BuiltinSerializers.kt
+++ b/core/commonMain/src/kotlinx/serialization/builtins/BuiltinSerializers.kt
@@ -194,25 +194,21 @@ public fun <K, V> MapSerializer(
 /**
  * Returns serializer for [UInt].
  */
-@ExperimentalUnsignedTypes
 public fun UInt.Companion.serializer(): KSerializer<UInt> = UIntSerializer
 
 /**
  * Returns serializer for [ULong].
  */
-@ExperimentalUnsignedTypes
 public fun ULong.Companion.serializer(): KSerializer<ULong> = ULongSerializer
 
 /**
  * Returns serializer for [UByte].
  */
-@ExperimentalUnsignedTypes
 public fun UByte.Companion.serializer(): KSerializer<UByte> = UByteSerializer
 
 /**
  * Returns serializer for [UShort].
  */
-@ExperimentalUnsignedTypes
 public fun UShort.Companion.serializer(): KSerializer<UShort> = UShortSerializer
 
 /**
diff --git a/core/commonMain/src/kotlinx/serialization/internal/ValueClasses.kt b/core/commonMain/src/kotlinx/serialization/internal/ValueClasses.kt
index b2657d656..90c1f28d3 100644
--- a/core/commonMain/src/kotlinx/serialization/internal/ValueClasses.kt
+++ b/core/commonMain/src/kotlinx/serialization/internal/ValueClasses.kt
@@ -10,7 +10,6 @@ import kotlinx.serialization.descriptors.*
 import kotlinx.serialization.encoding.*
 
 @PublishedApi
-@ExperimentalUnsignedTypes
 internal object UIntSerializer : KSerializer<UInt> {
     override val descriptor: SerialDescriptor = InlinePrimitiveDescriptor("kotlin.UInt", Int.serializer())
 
@@ -24,7 +23,6 @@ internal object UIntSerializer : KSerializer<UInt> {
 }
 
 @PublishedApi
-@ExperimentalUnsignedTypes
 internal object ULongSerializer : KSerializer<ULong> {
     override val descriptor: SerialDescriptor = InlinePrimitiveDescriptor("kotlin.ULong", Long.serializer())
 
@@ -38,7 +36,6 @@ internal object ULongSerializer : KSerializer<ULong> {
 }
 
 @PublishedApi
-@ExperimentalUnsignedTypes
 internal object UByteSerializer : KSerializer<UByte> {
     override val descriptor: SerialDescriptor = InlinePrimitiveDescriptor("kotlin.UByte", Byte.serializer())
 
@@ -52,7 +49,6 @@ internal object UByteSerializer : KSerializer<UByte> {
 }
 
 @PublishedApi
-@ExperimentalUnsignedTypes
 internal object UShortSerializer : KSerializer<UShort> {
     override val descriptor: SerialDescriptor = InlinePrimitiveDescriptor("kotlin.UShort", Short.serializer())
 
diff --git a/docs/builtin-classes.md b/docs/builtin-classes.md
index 018311545..eddfbdf90 100644
--- a/docs/builtin-classes.md
+++ b/docs/builtin-classes.md
@@ -68,8 +68,6 @@ Their natural representation in JSON is used.
 
 <!--- TEST -->
 
-> Experimental unsigned numbers as well as other experimental inline classes are not supported by Kotlin Serialization yet. 
-
 
 ### Long numbers
 
diff --git a/formats/json/commonMain/src/kotlinx/serialization/json/JsonElementSerializers.kt b/formats/json/commonMain/src/kotlinx/serialization/json/JsonElementSerializers.kt
index a6d0d0f41..6fcfa2c0a 100644
--- a/formats/json/commonMain/src/kotlinx/serialization/json/JsonElementSerializers.kt
+++ b/formats/json/commonMain/src/kotlinx/serialization/json/JsonElementSerializers.kt
@@ -109,7 +109,7 @@ private object JsonLiteralSerializer : KSerializer<JsonLiteral> {
     override val descriptor: SerialDescriptor =
         PrimitiveSerialDescriptor("kotlinx.serialization.json.JsonLiteral", PrimitiveKind.STRING)
 
-    @OptIn(ExperimentalUnsignedTypes::class, ExperimentalSerializationApi::class)
+    @OptIn(ExperimentalSerializationApi::class)
     override fun serialize(encoder: Encoder, value: JsonLiteral) {
         verify(encoder)
         if (value.isString) {
diff --git a/formats/json/commonMain/src/kotlinx/serialization/json/internal/Composers.kt b/formats/json/commonMain/src/kotlinx/serialization/json/internal/Composers.kt
index d3860d21b..553d6358e 100644
--- a/formats/json/commonMain/src/kotlinx/serialization/json/internal/Composers.kt
+++ b/formats/json/commonMain/src/kotlinx/serialization/json/internal/Composers.kt
@@ -41,7 +41,6 @@ internal open class Composer(@JvmField internal val sb: JsonStringBuilder) {
     fun printQuoted(value: String): Unit = sb.appendQuoted(value)
 }
 
-@ExperimentalUnsignedTypes
 internal class ComposerForUnsignedNumbers(sb: JsonStringBuilder, private val forceQuoting: Boolean) : Composer(sb) {
     override fun print(v: Int) {
         if (forceQuoting) printQuoted(v.toUInt().toString()) else print(v.toUInt().toString())
diff --git a/formats/json/commonMain/src/kotlinx/serialization/json/internal/StreamingJsonDecoder.kt b/formats/json/commonMain/src/kotlinx/serialization/json/internal/StreamingJsonDecoder.kt
index 9c6ba7429..834e59770 100644
--- a/formats/json/commonMain/src/kotlinx/serialization/json/internal/StreamingJsonDecoder.kt
+++ b/formats/json/commonMain/src/kotlinx/serialization/json/internal/StreamingJsonDecoder.kt
@@ -17,7 +17,7 @@ import kotlin.jvm.*
 /**
  * [JsonDecoder] which reads given JSON from [AbstractJsonLexer] field by field.
  */
-@OptIn(ExperimentalSerializationApi::class, ExperimentalUnsignedTypes::class)
+@OptIn(ExperimentalSerializationApi::class)
 internal open class StreamingJsonDecoder(
     final override val json: Json,
     private val mode: WriteMode,
@@ -354,7 +354,6 @@ internal open class StreamingJsonDecoder(
 }
 
 @OptIn(ExperimentalSerializationApi::class)
-@ExperimentalUnsignedTypes
 internal class JsonDecoderForUnsignedTypes(
     private val lexer: AbstractJsonLexer,
     json: Json
diff --git a/formats/json/commonMain/src/kotlinx/serialization/json/internal/StreamingJsonEncoder.kt b/formats/json/commonMain/src/kotlinx/serialization/json/internal/StreamingJsonEncoder.kt
index d2d9985b7..0fe6371e5 100644
--- a/formats/json/commonMain/src/kotlinx/serialization/json/internal/StreamingJsonEncoder.kt
+++ b/formats/json/commonMain/src/kotlinx/serialization/json/internal/StreamingJsonEncoder.kt
@@ -12,7 +12,6 @@ import kotlinx.serialization.json.*
 import kotlinx.serialization.modules.*
 import kotlin.native.concurrent.*
 
-@OptIn(ExperimentalUnsignedTypes::class)
 @SharedImmutable
 private val unsignedNumberDescriptors = setOf(
     UInt.serializer().descriptor,
@@ -24,7 +23,7 @@ private val unsignedNumberDescriptors = setOf(
 internal val SerialDescriptor.isUnsignedNumber: Boolean
     get() = this.isInline && this in unsignedNumberDescriptors
 
-@OptIn(ExperimentalSerializationApi::class, ExperimentalUnsignedTypes::class)
+@OptIn(ExperimentalSerializationApi::class)
 internal class StreamingJsonEncoder(
     private val composer: Composer,
     override val json: Json,
diff --git a/formats/json/commonMain/src/kotlinx/serialization/json/internal/TreeJsonDecoder.kt b/formats/json/commonMain/src/kotlinx/serialization/json/internal/TreeJsonDecoder.kt
index 55e23a13b..fd2831187 100644
--- a/formats/json/commonMain/src/kotlinx/serialization/json/internal/TreeJsonDecoder.kt
+++ b/formats/json/commonMain/src/kotlinx/serialization/json/internal/TreeJsonDecoder.kt
@@ -161,7 +161,6 @@ private sealed class AbstractJsonTreeDecoder(
         return this as? JsonLiteral ?: throw JsonDecodingException(-1, "Unexpected 'null' when $type was expected")
     }
 
-    @OptIn(ExperimentalUnsignedTypes::class)
     override fun decodeTaggedInline(tag: String, inlineDescriptor: SerialDescriptor): Decoder =
         if (inlineDescriptor.isUnsignedNumber) JsonDecoderForUnsignedTypes(StringJsonLexer(getPrimitiveValue(tag).content), json)
         else super.decodeTaggedInline(tag, inlineDescriptor)
diff --git a/formats/json/commonMain/src/kotlinx/serialization/json/internal/TreeJsonEncoder.kt b/formats/json/commonMain/src/kotlinx/serialization/json/internal/TreeJsonEncoder.kt
index 5c167b93e..dfd4b2c05 100644
--- a/formats/json/commonMain/src/kotlinx/serialization/json/internal/TreeJsonEncoder.kt
+++ b/formats/json/commonMain/src/kotlinx/serialization/json/internal/TreeJsonEncoder.kt
@@ -101,7 +101,6 @@ private sealed class AbstractJsonTreeEncoder(
         putElement(tag, JsonPrimitive(value.toString()))
     }
 
-    @OptIn(ExperimentalUnsignedTypes::class)
     override fun encodeTaggedInline(tag: String, inlineDescriptor: SerialDescriptor): Encoder =
         if (inlineDescriptor.isUnsignedNumber) object : AbstractEncoder() {
             override val serializersModule: SerializersModule = json.serializersModule
diff --git a/formats/json/commonTest/src/kotlinx/serialization/features/inline/EncodeInlineElementTest.kt b/formats/json/commonTest/src/kotlinx/serialization/features/inline/EncodeInlineElementTest.kt
index 5c53be0ac..56a7f3d27 100644
--- a/formats/json/commonTest/src/kotlinx/serialization/features/inline/EncodeInlineElementTest.kt
+++ b/formats/json/commonTest/src/kotlinx/serialization/features/inline/EncodeInlineElementTest.kt
@@ -2,8 +2,6 @@
  * Copyright 2017-2022 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
  */
 
-@file:OptIn(ExperimentalUnsignedTypes::class)
-
 package kotlinx.serialization.features.inline
 
 import kotlinx.serialization.*
diff --git a/formats/json/commonTest/src/kotlinx/serialization/features/inline/InlineClassesTest.kt b/formats/json/commonTest/src/kotlinx/serialization/features/inline/InlineClassesTest.kt
index 1eedafae9..6b074b348 100644
--- a/formats/json/commonTest/src/kotlinx/serialization/features/inline/InlineClassesTest.kt
+++ b/formats/json/commonTest/src/kotlinx/serialization/features/inline/InlineClassesTest.kt
@@ -3,11 +3,6 @@
  */
 
 @file:Suppress("INLINE_CLASSES_NOT_SUPPORTED", "SERIALIZER_NOT_FOUND")
-@file:OptIn(ExperimentalUnsignedTypes::class)
-
-/*
- * Copyright 2017-2019 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
- */
 
 package kotlinx.serialization.features.inline
 
diff --git a/formats/json/commonTest/src/kotlinx/serialization/features/inline/UnsignedIntegersTest.kt b/formats/json/commonTest/src/kotlinx/serialization/features/inline/UnsignedIntegersTest.kt
index 26d67288f..3611fc27a 100644
--- a/formats/json/commonTest/src/kotlinx/serialization/features/inline/UnsignedIntegersTest.kt
+++ b/formats/json/commonTest/src/kotlinx/serialization/features/inline/UnsignedIntegersTest.kt
@@ -1,7 +1,5 @@
-@file:Suppress("INLINE_CLASSES_NOT_SUPPORTED", "SERIALIZER_NOT_FOUND")
-@file:OptIn(ExperimentalUnsignedTypes::class)
 /*
- * Copyright 2017-2020 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
+ * Copyright 2017-2022 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
  */
 
 package kotlinx.serialization.features.inline