v3.3.1

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Published 8 October 2025

Improvements

• Add a note about SSE session lifetime in KDoc (KTOR-8440)
• Update Kotlin to 2.2.20 (KTOR-8896)

Bugfixes

• NumberFormatException when Content-Length header value contains null bytes (KTOR-4828)
• SerializationException: Serializer for class 'ClientSSESession' is not found when server responds with JSON (KTOR-7631)
• Netty: loadConfiguration missing enableHttp2 and enableH2c properties (KTOR-8898)
• Netty: EmbeddedServer.stop always blocks for twice of shutdownGracePeriod (KTOR-8770)
• shutdownGracePeriod is used instead of shutdownTimeout in EmbeddedServer.stop() (KTOR-8771)
• Support serving static resources within bootJar (KTOR-8592)

v3.3.0

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Published 11 September 2025

Features

• Support for server side http2 without tls (h2c) (KTOR-4750)
• OpenAPI generation build extension preview (KTOR-8721)
• Serve static resources with caching headers and ETag based on sha256 of content (KTOR-6700)
• Jetty engine: Upgrade Jetty dependencies to the latest version 12 (KTOR-6734)
• Static content: Support a custom respond logic if the file is not found (KTOR-8496)
• Upgrade OkHttp to version 5.0.0 (KTOR-8652)
• WebRTC Client, Android + WASM (KTOR-7958)

Improvements

• SSE: Cannot read response body from SSEClientException (KTOR-8165)
• SSE: "SSEClientException: Content-Length mismatch" on saving response body in DefaultResponseValidation (KTOR-8753)
• var Route.staticRootFolder: File? should be deprecated (KTOR-5836)
• Add image/bmp to the ContentType (KTOR-8735)
• Add some missing image content types (KTOR-8624)
• Upgrade to Kotlin 2.2 (KTOR-8647)
• Bump Kotlin API level to 2.2 (KTOR-8637)
• CIO: The engine ignores system proxy settings (KTOR-5922)

Bugfixes

• Performance regression when using ContentEncoding and HttpRequestRetry since 3.2.0 (KTOR-8820)
• Big number of simultaneous outbound web socket connections leads to a coroutine deadlock (KTOR-8829)
• DI: JobCancellationException during cleanup (KTOR-8785)
• Autoreloading: JobCancellationException when app is reloaded in the debugger since 3.2.0 (KTOR-8810)
• HttpRedirect: The client is redirected when no Location header in response (KTOR-8697)
• SerializationException when Application.propertyOrNull() is called with type Map<String, Any?> (KTOR-8781)
• "Failed resolution of: Ljava/lang/management/ManagementFactory" on Android when JvmGcMetrics are initialized (KTOR-8714)
• HttpCache: all header values but first in HttpResponse.varyKeys() are ignored (KTOR-6402)
• HttpCache: plugin selects wrong cache entry when filtering Vary headers with different case (KTOR-7621)
• CountedByteWriteChannel: autoFlush of the source channel doesn't make the channel auto flushing (KTOR-8411)