GWT is a Java to JavaScript compiler and web framework.

What is GWT?

GWT, formerly known as Google Web Toolkit, is a Java to JavaScript compiler and web framework. GWT is open sourced, Apache 2 licensed, and maintained by an active steering committee with members from companies building on GWT, among others Vaadin.

The core idea in GWT is that you can write your user interface in a structured language with good tooling (i.e. Eclipse or Maven) and you can share code with your existing server-side implementation. The GWT community is very active with some 100 000 users every month.

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What is Vaadin's relation to GWT?

As a Vaadin developer, it's not necessary for you to know about the existence of GWT. In fact, if you're using Vaadin or planning on using it, a much better resource for learning about Vaadin is

Vaadin uses GWT for compiling the widgets from Java to JavaScript. This allows you to write the client-side representation and logic in Java and have all the benefits of a statically typed language instead of using JavaScript - which is also fully supported. To maximize productivity you can write the user interface fully in the server-side Java and thus skip writing and compiling any code for the client.

Whether you want to use the Java to JavaScript compiler directly is up to you. In any case, the GWT based compiler is such a fundamental part of Vaadin core that it is built right in and is integrated as seamlessly as the JVM and HTML5 platforms Vaadin builds on.

GWT is a powerful technology that Vaadin utilizes and thus we want to see the GWT community thrive and to contribute back to it. Vaadin organizes the largest GWT conference in the world, GWT.create, and helps to market GWT. All the fixes we make to GWT in Vaadin contribute back upstream.

Widgets for GWT developers

If you are building your application with GWT (i.e. without Vaadin Framework), Vaadin also offers widgets for you to use. You can use the Vaadin GWT Polymer Elements package if you wish to use the Material Design web components, built by the Google Polymer team, in your GWT application. You can also use the Vaadin Grid component independently of the Vaadin Framework, by using the Vaadin Widgets package. You can download both packages from the Download section.

Vaadin and GWT


Vaadin's core utilizes GWT and heavily depends on it. Without GWT, Vaadin wouldn't be what it is today.


All bug fixes and features created for Vaadin or our support customers are automatically committed upstream back to the GWT core.


Vaadin is an active member in the GWT Steering Committee, helping steer the future of GWT.