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 0.55.0 released

September 2025

We're pleased to announce the availability of Eclipse OpenJ9 v0.55.0.

This release supports OpenJDK 25. For more information about supported platforms and OpenJDK versions, see Supported environments.

The 0.54.0 release updates that are applicable in the 0.55.0 release include the following:

The new JDK Flight Recorder (JFR) events, ModuleExports and ModuleRequires are added.

Other updates in the 0.55.0 release include the following:

XL C++ Runtime 17.1.3.0 or later is required for AIX OpenJ9 builds.
A new system property, -Djava.security.propertiesList is added that you can use to specify a list of different java.security property files that have the profiles you want instead of putting those different profiles into a single java.security file.
This is an OpenJDK change in the OpenJDK versions maintained to support building with OpenJ9.
The format of the java.vm.version system property value is updated to be compatible with the Runtime.Version parser.

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

Performance highlights of the 0.54.0 release that is applicable for the 0.55.0 release also include the following:

More Java Class Library intrinsics are being accelerated now across platforms.

Eclipse OpenJ9 version 0.53.0 released

July 2025

We're pleased to announce the availability of Eclipse OpenJ9 v0.53.0.

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

Other updates in this release include the following:

RHEL 8.8 and 9.2 are out of support. RHEL 8.10 and 9.4 are the new minimum operating system levels.
OpenSSL native cryptographic support is added for the Password based key derivation (PBKDF2) algorithm, providing improved cryptographic performance.
OpenSSL 3.5.1 is supported and bundled on all platforms. You can use the jdk.native.openssl.skipBundled property to specify whether to load the pre-packaged OpenSSL library or the library available on the system path.
Offheap support is added for the balanced GC policy.
The following new JDK Flight Recorder (JFR) events are added in this release:
- NativeLibrary (Linux® only)
- SystemGC
- SystemProcess (Linux only)
- YoungGenerationConfiguration

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

Performance highlights include the following:

Now the balanced GC policy always uses a contiguous representation of array data, which is stored in a special Offheap area for large arrays. It replaces arraylets, which had a discontiguous representation for large arrays. Balanced GC performance is improved for both Java code that deals with any size of array and native code that uses JNI Critical API with large arrays.
Several Java Class Library methods were optimized by the VM to increase throughput performance.