Eclipse OpenJ9 is a high-performance, scalable Java Virtual Machine implementation — contributed by IBM and representing thousands of person-years of engineering effort.
OpenJ9 is optimized for cloud, enterprise, and container environments — delivering fast startup, low memory footprint, and sustained throughput.
Ahead-of-Time (AOT) compilation and shared class caches dramatically cut startup latency, even in containerized workloads.
Idle-time optimization, compaction, and container-aware memory management keep heap usage lean — reducing cloud cost.
Choose from multiple garbage collection policies — gencon, balanced, metronome, and more — tuned to your application's workload profile.
Advanced JIT with GPU offload capability and -Xtune:virtualized mode for maximizing throughput in multi-tenant cloud environments.
Reduce startup time across multiple JVM instances by sharing class bytecodes and AOT-compiled methods via a persistent shared class cache.
Eclipse OpenJ9 represents thousands of person-years of engineering effort, powering the IBM SDK, Java Technology Edition, IBM Semeru Runtimes, and many core IBM Enterprise software products.
Contributed in 2017 to the Eclipse Foundation, OpenJ9 continues to evolve through wider community collaboration — driving fresh innovation and shaping the future of the Java platform for enterprise and cloud-native workloads.
vs. HotSpot — Open Liberty on OpenJDK 17
Lower is better. OpenJ9 as % of HotSpot.
Released September 2026 — supports OpenJDK 27.
This release brings several significant improvements to bootstrap class loading, ZIP handling, and platform compatibility.
The success of OpenJ9 is underpinned by the generosity of our supporters — through people, systems, data centres, and financial resources.
OpenJ9 is a community-driven project. Whether you are a user, adopter, or contributor — we'd love to hear from you.
Ask questions and chat directly with OpenJ9 developers. Whether you have a usage question, an improvement idea, or a problem to discuss — we're here.
Join OpenJ9 Slack →Create issues to explore ideas, request new features, or report problems. Our welcoming repository is open to all.
See OpenJ9 Issues →Browse our archive of community talks, technical deep dives, and feature overviews on YouTube — covering everything from GC policies to JITServer.
Watch on YouTube →Stay up to date with release announcements, performance insights, and community news from the OpenJ9 team.
@openj9 on X →We welcome contributions in all shapes and forms — code, docs, website, testing, and more. Be a part of the project and share in our success.
Interested in JVM development? We'd love to hear your ideas and help you collaborate on the OpenJ9 codebase. Our Contributor Guide will get you started.
Contributor GuideThere are many ways to contribute beyond code — help us improve user documentation, the website, or translations. Every contribution matters.
Docs Repository