Our Story

Eclipse OpenJ9 is a high performance, scalable, Java virtual machine (JVM) implementation that represents hundreds of person-years of effort. Contributed to the Eclipse project by IBM, the OpenJ9 JVM underpins the IBM SDK, Java Technology Edition product that is a core component of many IBM Enterprise software products. Continued development of OpenJ9 at the Eclipse foundation ensures wider collaboration, fresh innovation, and the opportunity to influence the development of OpenJ9 for the next generation of Java applications.

Our supporters

The success of the OpenJ9 project is underpinned by the generosity of our supporters, to whom we would like to extend our thanks. This support comes in different forms; monetary, people, system, and data center resources. People resources help us to staff the planning, development, delivery, and support of OpenJ9 releases as well as pioneering new and innovative technologies. Dedicated systems and hosting services allow us to run automated build and test operations, which help ensure that quality and reliability is central to all our deliverables.

Join the conversation

Join us on Slack where you can ask questions and chat directly with our developers. Whether you simply have a question about using OpenJ9, an idea for improvement, or a problem you want to discuss, we'd love to hear from you.

Join OpenJ9 Slack

Like all great open source projects, we have a vibrant and busy GitHub repository where you can create issues to explore ideas, request new features, or report any difficulties you are having.

See OpenJ9 Issues

Participate in the Eclipse OpenJ9 project

Become a contributor

We welcome contributions to the project in all shapes and forms. If you are interested in JVM development, we'd love to hear your ideas and help you collaborate with us on the code base. There are other ways you can contribute too, such as working on our website and docs. Be a part of the project and share in our success!

Contributor Guide

Join community calls

Our regular calls are a great place to find out what is going on in the project. As well as discussing our release plans and development status, we often feature lightning talks by members of the community. For example, technical deep dives or overviews about new features. To see agendas and recordings, look in the Slack #planning channel.

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Eclipse OpenJ9 version 0.49.0 released

February 2025

We're pleased to announce the availability of Eclipse OpenJ9 v0.49.0.

This release supports OpenJDK 8, 11, 17, 21, and 23. For more information about supported platforms and OpenJDK versions, see Supported environments.

Other updates in this release include the following:

The shared classes cache generation number is incremented causing the VM to create new shared caches, rather than re-creating or reusing existing caches. To save space, all existing shared caches should be removed unless they are in use by an earlier release.
A new shared classes cache suboption -Xshareclasses:extraStartupHints=<number> is added to adjust the number of startup hints that can be stored in a shared cache.
subAllocator related -Xgc options are added to control the compressed reference allocation.
Support for JDK Flight Recorder (JFR) in the VM is provided as a technical preview for OpenJDK 11 and later running on Linux® x86 or Linux on AArch64 and the recording can be triggered with the jcmd tool.

To read more about these and other changes, see the OpenJ9 user documentation.

Performance highlights include the following:

POWER11 CPU recognition and exploitation are added to achieve optimal performance on new hardware.