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/bmpto 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)