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KotlinConf Keynote Recap

Today is a great day for the Kotlin community. KotlinConf, the inaugural Kotlin conference, opens today, and we’re really impressed that around 1200 attendees from all over the world have joined us in San Francisco. During the conference keynote, Andrey Breslav, the lead designer of Kotlin, has announced a few major developments around Kotlin, and now we’re sharing the news with everyone else.

Kotlin 1.2 RC

The first major announcement from the keynote is the release of Kotlin 1.2 Release Candidate. The new features in this release include the experimental support for multiplatform projects, allowing you to share code between modules targeting the JVM and JavaScript, as well as several language improvements, including support for array literals in annotations. For more information about the new features in 1.2, please check out the Kotlin 1.2 Beta announcement blog post.

The compiler now rejects binaries compiled with earlier pre-release versions of Kotlin 1.2; you’ll need to recompile them with this release. Code compiled with Kotlin 1.0.x or 1.1.x is, of course, fully compatible with this release of the compiler.

Even though coroutines are still labeled as an experimental feature, we’d like to clarify the exact meaning of this status. Coroutines are fully ready to be used in production, we’re using them in our own development, and we’re not aware of any major issues with the implementation. The reason why we keep the experimental status is that it gives us the ability to iterate on the design. Note that, even if we do make changes to the API, the current API will remain supported, even though it will be marked as deprecated, and we will provide the necessary migration tools. According to our current plans, the experimental status of coroutines will be removed in Kotlin 1.3.

Now is the time when we ask for your help. Even though we’ve done a lot of testing of this release internally and with other teams at JetBrains, the real world is far more varied than what we have access to. Therefore, please — give Kotlin 1.2 RC a try on your own projects, and let us know if you run into any issues. Your help is essential in ensuring a smooth final release.
Tell everyone to go try it

Kotlin/Native iOS Support

The next big news we’ve announced is support for iOS development with Kotlin/Native, released as part of Kotlin/Native 0.4. This support is still in its early days, but it’s there, and it’s a major step on our path of enabling Kotlin development on all platforms.

To show what’s possible, we wrote two apps and published them to the App Store:

  • The Spinner app (GitHub) is a simple game built using OpenGL. It runs on both iOS and Android (play store link), and most of the code is shared between the two versions. The iOS version has several additional features such as Game Center integration.
  • The KotlinConf app (GitHub) shows you the schedule of this conference, and has a fully native iOS UI built with UIKit.

Both of the sample apps are open-source, and you can use them as a template to build your own cross-platform mobile apps in pure Kotlin.

Kotlin/Native IDE Support

Of course, you need an IDE to be productive with any language, and starting today, Kotlin/Native has IDE support too.
We’re now releasing an initial preview version of the Kotlin/Native plugin for CLion, our C/C++ IDE. The plugin supports CMake as the build system. It includes the full set of code editing features from the Kotlin plugin for IntelliJ IDEA, as well as initial support for project creation, testing and debugging.


To try the plugin, install CLion 2017.3 EAP and search for “Kotlin/Native” in the JetBrains plugins list.

In the coming days, we will publish a separate blog post with more details on the plugin and its features. And of course, the CLion plugin is only one step in our story for Kotlin IDE support; stay tuned for further announcements next year!

Ktor 0.9

Server-side development is also a key part of our multiplatform story. And now we’re announcing our own take on this part: the 0.9 release of Ktor, an awesome asynchronous coroutine-based Web framework built from the ground up in Kotlin.

Ktor is already being used in a number of projects both inside JetBrains and in the community, and now we’re confident that it’s a solid foundation for building very high-performance Web applications. Check out the quick start guides at, try it out and let us know what you think so we can make it even better for 1.0 release.

Creating Modern Web Apps with React and Kotlin

For Web front-end development with Kotlin, the biggest news for today is the release of official Kotlin wrappers for React.js, as well as create-react-kotlin-app, a toolbox for creating modern web applications in Kotlin using React.js. With create-react-kotlin-app you can generate and immediately start working on client-side apps without worrying about the project setup and build configuration, using the benefits of a statically typed language and the power of the JavaScript ecosystem.

To get started, run npm install -g create-react-kotlin-app and have a look at the Getting started guide.

Multiplatform Projects Demo

To show how all of the pieces in our multiplatform story fit together, we’ve built an app using all the latest bits of our technology stack: the KotlinConf app. It consists of the following components:

The backend, browser app and Android app share code using the Kotlin multiplatform project technology. For asynchronous programming, all components use coroutines. For exchanging the data between the server and the client, we use the brand new kotlinx.serialization library.

You’ll find the source code of the app a treasure trove of techniques that you will also be able to use in your own work.

Learning Kotlin

With all the buzz around Kotlin, there will be more and more people interested in learning the language. To make this easier, we’ve released a new version of the EduTools plugin, allowing to learn Kotlin by solving interactive exercises in your favorite IDE. The new version adds support for Android Studio (previously only IntelliJ IDEA was supported), and includes new UI for building your own courses.

Future Directions

As for the future evolution of the language, our main goal at this time is to enable better and broader code reuse between the platforms supported by Kotlin. We plan to extend the set of libraries available on all platforms with the same API to include I/O, networking, serialization, date handling and more.

In the compiler, our main focus for 1.3 will remain on internal changes, and not on externally visible language features. The internal changes will enable better performance, improved type inference, generation of more efficient code for all target platforms, as well as the much better responsiveness of the IDE plugins. We hope we’ll still be able to sweeten the release with some nice new language features, but we’re not making any promises at this time.

Let’s Kotlin!

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13 Responses to KotlinConf Keynote Recap

  1. Avatar

    Shai says:

    November 2, 2017

    FYI if you are more interested in a write once run anywhere Kotlin project you can do so with our Kotlin support for Codename One which can target native iOS, Android, Windows (UWP) and even web with a single code base and an API that should be very familiar to Swing developers.
    It’s all open source, integrates with IntelliJ and includes a cross platform GUI builder. It’s 100% extensible with plugins and full access to OS native code.

  2. Avatar

    Felix Scholz says:

    November 3, 2017

    Nice post! I’m so excited.

    I’ve tried using the Kotlin/Native plugin for CLion and it works so far with one exception: Windows is not being supported as “host”. I am not able to build the project using CMake.
    Is there some way to fix this? Is this just a bug?

    This is what I get: . I’ve not found another way to report this.

    • Avatar

      Scellow says:

      November 3, 2017

      I edited the CMakeKotlinInformation.cmake file to make it work on Windows

      Here it is:

      But i think it was on purpose, i can’t import package :/

  3. Avatar

    Adev says:

    November 3, 2017

    Thanks for the plugin for kotlin native, it was the only thing missing to really get into it!

    I/O, networking, serialization, date handling and more.

    That’s a really good news, thanks! it’ll avoid writting multiple platform specific “generic stuff”

    I knew it learning Kotlin was a good IDEA, thanks for all your hard work, Kotlin is the best <3

  4. Avatar

    jsbr says:

    November 3, 2017

    Where can I add issue for the “multiplatform projects”.

    A common project can only have one other common project as dependency. If I try to add another, there is no specific error message, but the compiler show a “Unresolved reference” exception for each class used in the second dependency.

    Do you plan to support this?
    Actually I have a “multiplatform project” (game for android/web) with many of other “multiplatform project” dependency

    • Avatar

      Alexander Udalov says:

      November 3, 2017


      Please report issues to the YouTrack at:


  5. Avatar

    innov8 says:

    November 4, 2017

    Kotlin native iOS support together with kotlin native IDE…. this is what we have been waiting for to move some significant projects to kotlin. iOS may still be early, but the first project we launch also be new so they can grow up together. And now we can use kotlin for this, we can also move the server code to keep module code reusable. Fantastic news!!!

  6. Avatar

    Nick says:

    November 4, 2017

    When is Kotlin 1.2 RC going to be released on SDK Man?

    • Avatar

      Dmitry Jemerov says:

      November 13, 2017

      We only publish stable Kotlin releases to SDKMan.

  7. Avatar

    Clancy says:

    November 4, 2017

    It’s great to see Kotlin maturing so rapidly.

    Will Kotlin/Native enable me to develop iOS & Android apps using some form of cross-platform GUI (like JavaFX) or one which I build myself based on OpenGL? I do not wish to be limited to native widgets on any OS.

    • Avatar

      Dmitry Jemerov says:

      November 13, 2017

      At this time we have no plans to build our own cross-platform UI toolkit. Using OpenGL to build your own UI is definitely possible.

  8. Avatar

    harry248 says:

    November 6, 2017

    Are you planning to support Kotlin/Native in your AppCode IDE?

    • Avatar

      Alexander Podkhalyuzin says:

      November 7, 2017

      It would be logical to have Kotlin/Native support in AppCode, so I would say yes, however I can’t give you concrete answer right now.