ZK brings the simplicity of desktop programming to Ajax development, thanks to its event driven and component based patterns.

All events, server push, system events and user activities alike, are encapsulated as generic events to be handled generically. All components are LEGO-like building blocks which allow developers to compose UI with ease.

In addition, ZK provides a markup language - ZUML, making the design of rich user interfaces as simple and fast as authoring HTML pages. No programming is required.

UI presentation can be done in XML without programming and compilation, so UI designers and business analysts can work together and experiment with different designs on-the-fly.

The process of UI design can be iterated quickly without Java programming, shortening the design phase and inspiring better design.

To fulfill the complex business requirements, ZK offers 200+ enterprise grade Ajax components right off the box so UI designers can easily find the right component for the right job.

ZUML enables developers to effectively embed scripting within the markup declarations so a fast proof of concept can be endowed with the behavior and functionalities of its intended purposes, for a quick project kick-off.

Developers are allowed to handle user interface using any one of the popular scripting languages, such as Groovy, Python, Ruby, and JavaScript. The BeanShell interpreter for Java is set as the default script interpreter

ZK is a Java based Ajax framework where instructions are executed at the server by default, Web application developers can continue to use their well versed Java language and all its proven enterprise technologies to develop ZK applications.

Developers can continue to use their favorite Java IDEs, debuggers, and profilers in their Web development. For Eclipse users, ZK offers ZK Studio, an Eclipse plugin released by the ZK team with features like WYSIWYG UI editor, component palette for easy drag-and-drop building of the UI presentation, and ZK MVC extractor for converting scripting done in the prototyping phase to Java classes, following the MVC pattern to decouple the View from Model and Control. A NetBeans plugin, REM, a contribution from ZK's community, is available for the NetBeans users.

ZK is component based and event driven, which simplifies Ajax application development to a desktop programming experience without having to be concerned with JavaScript programming, cross-browser issues, complex Ajax communications and other factors well noted for the high cost of Ajax Web development.

To facilitate automated testing, ZK offers a straight-forward testing language, ZTL, allowing developers to write test code in Java.

In addition, ZTL allows record and play functionalities to minimize the effort of test code writing.

ZTL works with JUnit and Selenium, and ZK applications have also been tested with popular load testing tools such as HP LoadRunner, Grinder, NeoLoad, among others.

ZK's pluggable architecture empowers developers with the flexibility to intercept and inject instructions through out the program execution.

Developers are given the utilities to analyze the statistics of timestamps of the request-response cycle for each Ajax request; from client request, server side processing, server response, to client side rendering.

Great efforts are taken to minimize the memory footprint of Ajax components on the server, such as rendering components as stateless when Ajax functionalities are not required. With ZK's Server+client Fusion architecture, developers can also create client-side objects which exist strictly in the browser without burdening the server resources.

Further more, user activities are grouped based on application's requirements and sent in batch to minimize network traffic.

All of these architectural innovations allows developers having full control of the Web application and greatly facilitates the performance tuning process.

The MVC pattern enforces the decoupling of View, Model, and Controller, making applications more flexible to change and easier to build.

The View can be implemented using ZK User Interface Markup Language (XML) without any programming; meanwhile, ZK automatically wires the UI components and user events to members in the Controller class.

ZK's programming free data-binding mechanism automates CRUD between UI components and the data source. Application developers only need to associate data objects with UI components using simple annotations in XML. Not a single line of Java code is required.

Whenever a view is loaded, the components will be initialized with values of their corresponding data objects. In the event that a data value is updated, the changes will reflect on the UI components. Similarly, data modified on the UI components would be updated to the associated data objects.

ZK's composite pattern offers developers a template based methodology to compose existing components as a new, reusable component.

The state and behavior of a composite component can be extended and encapsulated in a Java class to enhance its functionalities.

ZK's templating patterns allows a UI presentation to be dynamically composed with templates at runtime using simple annotations.

A UI presentation in ZK can be customized to satisfy its dependent context; may it be a specific look and feel for a selected group of users, or a set of functionalities enabled only for certain scenarios.

ZK’s 200+ components offer UI designers a variety of feature rich components to meet the demands of enterprise Ajax applications.

For data presentation, ZK offers the Grid, Listbox, and Tree components. All of which have built in paging, auto-sorting, grouping, load-on-demand, data binding support, frozen columns/rows, in-line editing, master detail, among others.

To outline an enterprise grade Ajax user interface, ZK offers a wide range of layout components and component attributes. For instance, a Portal Layout with drag-and-drop portal containers. A Border Layout that divides the page into collapsible and adjustable panels. All of which elevates your static 2D page to higher dimensions.

For professional reporting, ZK has integrated popular third party Ajax components such as JFreeChart, Flash Chart, Fusion Chart, Google Maps, CK Editor, SIMILE Timeline and Timeplots. In addition, the JasperReports component allows users to generate reports in PDF, HTML, XML, DOC, ODT, and XLS formats.

Components such as Captcha, Color-picker, File Uploader, among the vast and versatility ZK components, all play an integral part of what makes ZK a leading enterprise Ajax solution.

Functionalities are made to be shared among all components and controlled using the same set of APIs. For instance, the drag and drop feature is available to all ZK components and its handle is the same manner for all components.

ZK makes the behavior of components predictable so developers can easily learn and use to piece together sophisticated enterprise grade user interface.

ZK components are LEGO-like building blocks; this characteristic enables UI designers to tackle all sorts of UI requirements with the right combination of components and some imagination.

Furthermore, component composition can be made recursively. For instance, a Grid can be put into another Grid recursively to generate a hierarchical data representation. For another, text boxes can be placed in a List box to make in-place editing possible. This ability to piece together UI components freely makes ZK components incredibly versatile and extensible.

ZK allows a component to be fitted with various sets of DOM structures and behaviors, while its handle and APIs stay the same. Developers can use the same component for different visual representations and change the UI without modifying the application code.

For instance, a Grid can rendered as is, or with paging at top and/or bottom. Tabbox, Listbox, and Window are the few among many others that offers multiple representations.

Apache Tomcat, IBM WebSphere, IBM WebSphere Process Server, IBM WebSphere Portal, SAP NetWeaver, Spring tc Server, jBoss Application Server, BEA WebLogic, Oracle OC4J, Sun GlassFish, Jetty, Google App Engine, among other application server compliant with servlet 2.3 specification and above.

We believe open source is the best way to build an open, secure, and trustworthy software that millions can depend on.

ZK 5 CE is freely available under the open source LGPL license. It's free for open source as well as commercial development and deployment.

ZK PE & EE are freely available for open source GPL compliant projects under the ZK Open Source License.

ZK is open sourced, over 1,500,000 downloads to date across 190 countries, and growing strong.

As with any healthy open source software project, its community is the driving force behind ZK's evolution. The community depends on the ZK team to deliver a dependable Ajax framework to base their projects on. ZK relies on the feedback and support from the community to grow. ZK becomes more versatile as each feature request is implemented and the framework gets more stable as each reported bug is resolved.

ZK and its community together form a positive feedback loop that garner each other's momentum toward a greater open source Ajax ecosystem.

ZK is ranked #1 Ajax framework on SourceForge.

Code is committed to the ZK repository each day. A ZK version is released every couple of months, with a "freshly release" happening each day.

ZK is constantly moving forward to bring forth a reliable and feature rich framework on the Java platform.

Hundreds of open source projects extends, or depends on ZK; ZKGrails and NetBeans REM are two prime examples of quality projects contributed by the great community.

With tens of thousands of members world wide, enthusiastic "Zeeks" share their development experiences and visions in user groups and forums.

The ZK framework has been translated to 23 languages by the community, and the source code has been reviewed by experts across fields and industries. Thousands of test cases have been contributed by the community. Hundreds of articles and tutorials on easily accessible on the Internet.

ZK has a solid track record as the trusted framework of choice across industries.

With over 1,500,000 downloads, ZK empowers a wide variety of companies and institutions, ranging from small to large in multiple industries. Over one hundred Fortune 500 companies, such as Deutsche Bank, Barclays, Sony, Swiss RE, Societe Generale, Lloyds TSB, Oracle, Bank of America and Toyota, and organizations such as US Department of Defense, University of Oxford, United Nations, rely on ZK to power mission critical systems.

Over 90% of our customers renew our services each year because the technological advantage ZK offers, and also the ZK team's devotion to the success of the clients' mission critical projects.

Tens of thousands of developers choose ZK to build their mission critical projects on, including multi-million dollar systems that serve millions of users and thousands of concurrent ones on an international scale.

The adoption of ZK is approved in projects within organizations that take strict security measures, such as Department of Defense in US as well as many large international financial firms and health care providers.

Innovation is the most important force driving the ZK team forward. ZK delivered the first Server+client Fusion technology, the first embeddable Ajax spreadsheet, the first Ajax framework to support Java and Android phones, the first to synergize the power of pure Java, markup and script languages, and more.

ZK's support team is always dedicated to the success of your project. The ZK core developers who develop the framework are at your disposal to review your code, identify performance bottlenecks, customize and resolve any challenges arose in the development process. Help comes in the form of online or onsite training, consulting, and email incident supports.