diff --git a/ktor-client/ktor-client-plugins/ktor-client-content-negotiation/common/src/io/ktor/client/plugins/contentnegotiation/JsonContentTypeMatcher.kt b/ktor-client/ktor-client-plugins/ktor-client-content-negotiation/common/src/io/ktor/client/plugins/contentnegotiation/JsonContentTypeMatcher.kt
index fdf137e8b90..0e0ec736efd 100644
--- a/ktor-client/ktor-client-plugins/ktor-client-content-negotiation/common/src/io/ktor/client/plugins/contentnegotiation/JsonContentTypeMatcher.kt
+++ b/ktor-client/ktor-client-plugins/ktor-client-content-negotiation/common/src/io/ktor/client/plugins/contentnegotiation/JsonContentTypeMatcher.kt
@@ -1,5 +1,5 @@
 /*
- * Copyright 2014-2022 JetBrains s.r.o and contributors. Use of this source code is governed by the Apache 2.0 license.
+ * Copyright 2014-2024 JetBrains s.r.o and contributors. Use of this source code is governed by the Apache 2.0 license.
  */
 
 package io.ktor.client.plugins.contentnegotiation
@@ -16,6 +16,6 @@ public object JsonContentTypeMatcher : ContentTypeMatcher {
         }
 
         val value = contentType.withoutParameters().toString()
-        return value.startsWith("application/") && value.endsWith("+json")
+        return value.startsWith("application/", ignoreCase = true) && value.endsWith("+json", ignoreCase = true)
     }
 }
diff --git a/ktor-client/ktor-client-plugins/ktor-client-json/common/src/io/ktor/client/plugins/json/JsonContentTypeMatcher.kt b/ktor-client/ktor-client-plugins/ktor-client-json/common/src/io/ktor/client/plugins/json/JsonContentTypeMatcher.kt
index 8e4181ed050..5d660ad8693 100644
--- a/ktor-client/ktor-client-plugins/ktor-client-json/common/src/io/ktor/client/plugins/json/JsonContentTypeMatcher.kt
+++ b/ktor-client/ktor-client-plugins/ktor-client-json/common/src/io/ktor/client/plugins/json/JsonContentTypeMatcher.kt
@@ -1,6 +1,6 @@
 /*
-* Copyright 2014-2021 JetBrains s.r.o and contributors. Use of this source code is governed by the Apache 2.0 license.
-*/
+ * Copyright 2014-2024 JetBrains s.r.o and contributors. Use of this source code is governed by the Apache 2.0 license.
+ */
 
 package io.ktor.client.plugins.json
 
@@ -13,6 +13,6 @@ internal class JsonContentTypeMatcher : ContentTypeMatcher {
         }
 
         val value = contentType.withoutParameters().toString()
-        return value.startsWith("application/") && value.endsWith("+json")
+        return value.startsWith("application/", ignoreCase = true) && value.endsWith("+json", ignoreCase = true)
     }
 }
diff --git a/ktor-server/ktor-server-jetty-jakarta/jvm/src/io/ktor/server/jetty/jakarta/JettyKtorHandler.kt b/ktor-server/ktor-server-jetty-jakarta/jvm/src/io/ktor/server/jetty/jakarta/JettyKtorHandler.kt
index 50b9a6ab496..9d1d522a7fe 100644
--- a/ktor-server/ktor-server-jetty-jakarta/jvm/src/io/ktor/server/jetty/jakarta/JettyKtorHandler.kt
+++ b/ktor-server/ktor-server-jetty-jakarta/jvm/src/io/ktor/server/jetty/jakarta/JettyKtorHandler.kt
@@ -1,5 +1,5 @@
 /*
- * Copyright 2014-2023 JetBrains s.r.o and contributors. Use of this source code is governed by the Apache 2.0 license.
+ * Copyright 2014-2024 JetBrains s.r.o and contributors. Use of this source code is governed by the Apache 2.0 license.
  */
 
 package io.ktor.server.jetty.jakarta
@@ -8,7 +8,6 @@ import io.ktor.http.*
 import io.ktor.server.application.*
 import io.ktor.server.engine.*
 import io.ktor.server.response.*
-import io.ktor.util.*
 import io.ktor.util.cio.*
 import io.ktor.util.pipeline.*
 import io.ktor.utils.io.*
@@ -72,7 +71,7 @@ internal class JettyKtorHandler(
     ) {
         try {
             val contentType = request.contentType
-            if (contentType != null && contentType.startsWith("multipart/")) {
+            if (contentType != null && contentType.startsWith("multipart/", ignoreCase = true)) {
                 baseRequest.setAttribute(Request.__MULTIPART_CONFIG_ELEMENT, multipartConfig)
                 // TODO someone reported auto-cleanup issues so we have to check it
             }
diff --git a/ktor-server/ktor-server-jetty/jvm/src/io/ktor/server/jetty/JettyKtorHandler.kt b/ktor-server/ktor-server-jetty/jvm/src/io/ktor/server/jetty/JettyKtorHandler.kt
index f3a8bdbed68..38a12f972a8 100644
--- a/ktor-server/ktor-server-jetty/jvm/src/io/ktor/server/jetty/JettyKtorHandler.kt
+++ b/ktor-server/ktor-server-jetty/jvm/src/io/ktor/server/jetty/JettyKtorHandler.kt
@@ -1,5 +1,5 @@
 /*
- * Copyright 2014-2019 JetBrains s.r.o and contributors. Use of this source code is governed by the Apache 2.0 license.
+ * Copyright 2014-2024 JetBrains s.r.o and contributors. Use of this source code is governed by the Apache 2.0 license.
  */
 
 package io.ktor.server.jetty
@@ -8,7 +8,6 @@ import io.ktor.http.*
 import io.ktor.server.application.*
 import io.ktor.server.engine.*
 import io.ktor.server.response.*
-import io.ktor.util.*
 import io.ktor.util.cio.*
 import io.ktor.util.pipeline.*
 import io.ktor.utils.io.*
@@ -72,7 +71,7 @@ internal class JettyKtorHandler(
     ) {
         try {
             val contentType = request.contentType
-            if (contentType != null && contentType.startsWith("multipart/")) {
+            if (contentType != null && contentType.startsWith("multipart/", ignoreCase = true)) {
                 baseRequest.setAttribute(Request.MULTIPART_CONFIG_ELEMENT, multipartConfig)
                 // TODO someone reported auto-cleanup issues so we have to check it
             }