diff --git a/compiler/frontend/src/org/jetbrains/kotlin/diagnostics/rendering/DefaultErrorMessages.java b/compiler/frontend/src/org/jetbrains/kotlin/diagnostics/rendering/DefaultErrorMessages.java
index 61a295479b1..f612ecf5817 100644
--- a/compiler/frontend/src/org/jetbrains/kotlin/diagnostics/rendering/DefaultErrorMessages.java
+++ b/compiler/frontend/src/org/jetbrains/kotlin/diagnostics/rendering/DefaultErrorMessages.java
@@ -158,8 +158,8 @@ public class DefaultErrorMessages {
         MAP.put(EXPERIMENTAL_MARKER_CAN_ONLY_BE_USED_AS_ANNOTATION_OR_ARGUMENT_IN_USE_EXPERIMENTAL, "This class can only be used as an annotation or as an argument to @OptIn");
 
         MAP.put(USE_EXPERIMENTAL_WITHOUT_ARGUMENTS, "@OptIn without any arguments has no effect");
-        MAP.put(USE_EXPERIMENTAL_ARGUMENT_IS_NOT_MARKER, "Annotation ''{0}'' is not an experimental API marker, therefore its usage in @OptIn is ignored", TO_STRING);
-        MAP.put(EXPERIMENTAL_ANNOTATION_WITH_WRONG_TARGET, "Experimental annotation cannot be used on the following code elements: {0}. Please remove these targets", STRING);
+        MAP.put(USE_EXPERIMENTAL_ARGUMENT_IS_NOT_MARKER, "Annotation ''{0}'' is not an opt-in requirement marker, therefore its usage in @OptIn is ignored", TO_STRING);
+        MAP.put(EXPERIMENTAL_ANNOTATION_WITH_WRONG_TARGET, "Opt-in requirement marker annotation cannot be used on the following code elements: {0}. Please remove these targets", STRING);
 
         MAP.put(EXPERIMENTAL_UNSIGNED_LITERALS, "Unsigned literals are experimental and their usages should be marked with ''@{0}'' or ''@OptIn({0}::class)''", TO_STRING);
         MAP.put(EXPERIMENTAL_UNSIGNED_LITERALS_ERROR, "Unsigned literals are experimental and their usages must be marked with ''@{0}'' or ''@OptIn({0}::class)''", TO_STRING);
diff --git a/compiler/frontend/src/org/jetbrains/kotlin/resolve/checkers/ExperimentalUsageChecker.kt b/compiler/frontend/src/org/jetbrains/kotlin/resolve/checkers/ExperimentalUsageChecker.kt
index 56cf38f33dc..87996d09774 100644
--- a/compiler/frontend/src/org/jetbrains/kotlin/resolve/checkers/ExperimentalUsageChecker.kt
+++ b/compiler/frontend/src/org/jetbrains/kotlin/resolve/checkers/ExperimentalUsageChecker.kt
@@ -224,16 +224,16 @@ class ExperimentalUsageChecker(project: Project) : CallChecker {
             val deprecationResolver =
                 DeprecationResolver(LockBasedStorageManager("ExperimentalUsageChecker"), languageVersionSettings, CoroutineCompatibilitySupport.ENABLED, DeprecationSettings.Default)
 
-            // Returns true if fqName refers to a valid experimental API marker.
+            // Returns true if fqName resolves to a valid opt-in requirement marker.
             fun checkAnnotation(fqName: String): Boolean {
                 val descriptor = module.resolveClassByFqName(FqName(fqName), NoLookupLocation.FOR_NON_TRACKED_SCOPE)
                 if (descriptor == null) {
-                    reportWarning("Experimental API marker $fqName is unresolved. Please make sure it's present in the module dependencies")
+                    reportWarning("Opt-in requirement marker $fqName is unresolved. Please make sure it's present in the module dependencies")
                     return false
                 }
 
                 if (descriptor.loadExperimentalityForMarkerAnnotation() == null) {
-                    reportWarning("Class $fqName is not an experimental API marker annotation")
+                    reportWarning("Class $fqName is not an opt-in requirement marker")
                     return false
                 }
 
@@ -242,7 +242,7 @@ class ExperimentalUsageChecker(project: Project) : CallChecker {
                         DeprecationLevelValue.WARNING -> reportWarning
                         DeprecationLevelValue.ERROR, DeprecationLevelValue.HIDDEN -> reportError
                     }
-                    report("Experimental API marker $fqName is deprecated" + deprecation.message?.let { ". $it" }.orEmpty())
+                    report("Opt-in requirement marker $fqName is deprecated" + deprecation.message?.let { ". $it" }.orEmpty())
                 }
                 return true
             }
@@ -253,7 +253,7 @@ class ExperimentalUsageChecker(project: Project) : CallChecker {
             }
 
             for (fqName in validExperimental.intersect(validUseExperimental)) {
-                reportError("'-Xuse-experimental=$fqName' has no effect because '-Xexperimental=$fqName' is used")
+                reportError("'-Xopt-in=$fqName' has no effect because '-Xexperimental=$fqName' is used")
             }
         }
     }
diff --git a/compiler/testData/cli/jvm/experimentalAndUseExperimentalWithSameAnnotation.out b/compiler/testData/cli/jvm/experimentalAndUseExperimentalWithSameAnnotation.out
index fb8dd5e37fe..21c63f40df3 100644
--- a/compiler/testData/cli/jvm/experimentalAndUseExperimentalWithSameAnnotation.out
+++ b/compiler/testData/cli/jvm/experimentalAndUseExperimentalWithSameAnnotation.out
@@ -1,2 +1,2 @@
-error: '-Xuse-experimental=org.test.ExperimentalAPI' has no effect because '-Xexperimental=org.test.ExperimentalAPI' is used
+error: '-Xopt-in=org.test.ExperimentalAPI' has no effect because '-Xexperimental=org.test.ExperimentalAPI' is used
 COMPILATION_ERROR
diff --git a/compiler/testData/cli/jvm/experimentalDeprecated.out b/compiler/testData/cli/jvm/experimentalDeprecated.out
index 6208f5328d8..2dcf2329694 100644
--- a/compiler/testData/cli/jvm/experimentalDeprecated.out
+++ b/compiler/testData/cli/jvm/experimentalDeprecated.out
@@ -1,5 +1,5 @@
-error: experimental API marker org.test.Error1 is deprecated. Error1
-error: experimental API marker org.test.Hidden1 is deprecated. Hidden1
-error: experimental API marker org.test.Error2 is deprecated. Error2
-error: experimental API marker org.test.Hidden2 is deprecated. Hidden2
+error: opt-in requirement marker org.test.Error1 is deprecated. Error1
+error: opt-in requirement marker org.test.Hidden1 is deprecated. Hidden1
+error: opt-in requirement marker org.test.Error2 is deprecated. Error2
+error: opt-in requirement marker org.test.Hidden2 is deprecated. Hidden2
 COMPILATION_ERROR
diff --git a/compiler/testData/cli/jvm/experimentalDeprecatedWarning.out b/compiler/testData/cli/jvm/experimentalDeprecatedWarning.out
index 2e39236cf86..e179ed007bc 100644
--- a/compiler/testData/cli/jvm/experimentalDeprecatedWarning.out
+++ b/compiler/testData/cli/jvm/experimentalDeprecatedWarning.out
@@ -1,4 +1,4 @@
 warning: '-Xexperimental' is deprecated and will be removed in a future release
-warning: experimental API marker org.test.Warning2 is deprecated. Warning2
-warning: experimental API marker org.test.Warning1 is deprecated. Warning1
+warning: opt-in requirement marker org.test.Warning2 is deprecated. Warning2
+warning: opt-in requirement marker org.test.Warning1 is deprecated. Warning1
 OK
diff --git a/compiler/testData/cli/jvm/experimentalIsNotAnnotation.out b/compiler/testData/cli/jvm/experimentalIsNotAnnotation.out
index 6dfe842009e..5744caeba0f 100644
--- a/compiler/testData/cli/jvm/experimentalIsNotAnnotation.out
+++ b/compiler/testData/cli/jvm/experimentalIsNotAnnotation.out
@@ -1,4 +1,4 @@
 warning: '-Xexperimental' is deprecated and will be removed in a future release
-warning: class org.test.NotAnAnnotation1 is not an experimental API marker annotation
-warning: class org.test.NotAnAnnotation2 is not an experimental API marker annotation
+warning: class org.test.NotAnAnnotation1 is not an opt-in requirement marker
+warning: class org.test.NotAnAnnotation2 is not an opt-in requirement marker
 OK
diff --git a/compiler/testData/cli/jvm/experimentalIsNotMarker.out b/compiler/testData/cli/jvm/experimentalIsNotMarker.out
index 9b1b17a0e60..d42e2fc588e 100644
--- a/compiler/testData/cli/jvm/experimentalIsNotMarker.out
+++ b/compiler/testData/cli/jvm/experimentalIsNotMarker.out
@@ -1,4 +1,4 @@
 warning: '-Xexperimental' is deprecated and will be removed in a future release
-warning: class org.test.NotAMarker1 is not an experimental API marker annotation
-warning: class org.test.NotAMarker2 is not an experimental API marker annotation
+warning: class org.test.NotAMarker1 is not an opt-in requirement marker
+warning: class org.test.NotAMarker2 is not an opt-in requirement marker
 OK
diff --git a/compiler/testData/cli/jvm/experimentalUnresolved.out b/compiler/testData/cli/jvm/experimentalUnresolved.out
index d2ede251b56..3cf3a857584 100644
--- a/compiler/testData/cli/jvm/experimentalUnresolved.out
+++ b/compiler/testData/cli/jvm/experimentalUnresolved.out
@@ -1,5 +1,5 @@
 warning: '-Xexperimental' is deprecated and will be removed in a future release
-warning: experimental API marker org.test.Unresolved2 is unresolved. Please make sure it's present in the module dependencies
-warning: experimental API marker org.test.Unresolved1 is unresolved. Please make sure it's present in the module dependencies
-warning: experimental API marker org.test.Unresolved3 is unresolved. Please make sure it's present in the module dependencies
+warning: opt-in requirement marker org.test.Unresolved2 is unresolved. Please make sure it's present in the module dependencies
+warning: opt-in requirement marker org.test.Unresolved1 is unresolved. Please make sure it's present in the module dependencies
+warning: opt-in requirement marker org.test.Unresolved3 is unresolved. Please make sure it's present in the module dependencies
 OK