Eclipse Temurin and OpenJDK are closely related but not identical: Temurin is a production-ready, TCK (Technology Compatibility Kit) certified distribution built from OpenJDK sources, while upstream OpenJDK provides only six-month release cycles with no long-term support. For teams that need stability, Temurin or Azul Zulu fills the gap by providing LTS versions and verified compatibility that vanilla OpenJDK does not offer.
OpenJDK is the open-source reference implementation of the Java Platform, Standard Edition. Every major JDK distribution including Temurin, Azul Zulu, Amazon Corretto, and Oracle JDK builds on top of OpenJDK source code. The project ships a new release every six months, but each release receives only six months of security patches before becoming unsupported. That rapid cadence works for cutting-edge projects but creates serious challenges for enterprise teams that need years of patch support on a stable version.
Eclipse Temurin, maintained by the Eclipse Adoptium working group, was purpose-built to solve this problem. It takes OpenJDK source code and adds regular LTS build releases for Java versions 8, 11, 17, 21, and 25, rigorous TCK testing, and broadly compatible binary packages for the most common platforms. Understanding when to choose Temurin versus going straight to OpenJDK, or picking an alternative like Azul Zulu, is critical for any team planning a long-term Java deployment strategy.
What Is OpenJDK?
OpenJDK (Open Java Development Kit) is the official open-source implementation of Java SE, governed by Oracle and developed by a broad community of contributors. It is the canonical source code base from which virtually all JDK distributions are derived. OpenJDK releases follow a strict six-month cadence: a new version ships every March and September. Only the most recent version receives active security updates; older releases are considered end-of-life immediately.
This model is ideal for developers who want the very latest Java language features and can stay current with every release. However, it is poorly suited to production environments that require multi-year stability. Teams running critical workloads rarely upgrade their JDK every six months, making vanilla OpenJDK a risky choice for anything beyond developer workstations or short-lived containers.
What Is Eclipse Temurin?
Eclipse Temurin is a free, open-source JDK distribution produced by the Eclipse Adoptium project. It is built from OpenJDK source code but ships as pre-built, fully tested binaries compatible with the major server platforms: x64 and ARM64 Linux, Windows, and macOS. Temurin is the direct successor to the AdoptOpenJDK project, which migrated to Eclipse Adoptium in 2021 and rebranded its HotSpot-based builds as Temurin.
Temurin’s primary value proposition is LTS support: it provides long-term patch streams for Java 8, 11, 17, 21, and 25, the versions enterprises actually run in production. All Temurin builds are TCK-certified, meaning they pass Oracle’s official Java compatibility test suite. Support is community-driven through the Eclipse Adoptium mailing lists and GitHub issue tracker, with no paid commercial support tier offered.
Temurin vs OpenJDK Comparison
| Feature | Eclipse Temurin | OpenJDK |
|---|---|---|
| License | GPLv2 + Classpath Exception | GPLv2 + Classpath Exception |
| Cost | Free | Free |
| Support | Community only | None (self-serve) |
| LTS Versions | 8, 11, 17, 21, 25 | None (rolling releases) |
| Performance | HotSpot JVM | HotSpot JVM (reference) |
| Platforms | x64/ARM Linux, Windows, macOS | Linux x64 primarily |
| TCK Certified | Yes | TCK-certified (Oracle upstream builds) |
Licensing and Cost
Both OpenJDK and Eclipse Temurin are released under the GNU General Public License v2 with the Classpath Exception, making them free for production use with no royalties or license fees. This stands in direct contrast to Oracle Java SE, which requires a paid subscription for production deployments since January 2019. Neither OpenJDK nor Temurin imposes any usage restrictions beyond the GPL terms, and both can be freely redistributed as part of larger products.
Azul Zulu, another OpenJDK distribution from Azul Systems, is also free under the same license terms. Like Temurin, Zulu is TCK-certified. Unlike Temurin, Zulu offers commercial support through Azul Core, giving enterprises that need SLA-backed patches and dedicated engineering a paid option without switching to Oracle. Zulu covers Java versions 6 through 25 and beyond, and a broader range of operating systems including Alpine Linux (musl libc); Solaris is available in archived Zulu releases.
Performance and Support
Both OpenJDK and Temurin use the HotSpot JVM, so raw runtime performance between the two is essentially identical for the same Java version. Neither distribution makes JVM-level performance modifications to the upstream source; any benchmark differences between JDK distributions at the same version are attributable to JVM flags or GC tuning, not the distribution itself.
Where the distributions diverge sharply is long-term support. Vanilla OpenJDK provides no backported security fixes beyond the current release. If a critical CVE is discovered in Java 17 after the release of Java 21, mainline OpenJDK offers no patch for Java 17, although the community OpenJDK 17u Updates project maintains source-level backports. Eclipse Temurin fills this gap with community-maintained backport patches for its LTS versions. However, community support means no SLA: if a zero-day CVE surfaces, the Adoptium community responds as quickly as it can, but there is no contracted response time.
For enterprises that require a contracted patch SLA, Azul Core (built on Azul Zulu) provides paid support with defined response times, dedicated engineering resources, and the option for extended LTS coverage on older Java versions. This makes Azul Core a compelling alternative when community-only response timelines are insufficient for compliance or security requirements.
Which Should You Choose?
Choose vanilla OpenJDK if you are developing new applications and plan to stay on the latest Java release, running in short-lived containers or CI pipelines where frequent upgrades are easy and expected. The reference builds are appropriate for this use case.
Choose Eclipse Temurin if you need a free, community-supported LTS build for production workloads on standard platforms such as x64 or ARM64 Linux, Windows, or macOS, and are comfortable relying on community-speed security patches. Temurin is a solid choice for teams that want a vendor-neutral distribution with no commercial obligations.
Choose Azul Zulu and Azul Core if you need broader platform support including Alpine Linux, Solaris, or less common architectures; support for Java versions outside Temurin’s LTS range such as Java 6, 7, or non-LTS releases; or a commercial SLA for security patches and support. Zulu gives you a clear migration path from free to fully supported without changing your JDK distribution.
Frequently Asked Questions
Is Eclipse Temurin the same as OpenJDK?
No. Eclipse Temurin is built from OpenJDK source code but is a distinct, separately packaged distribution. Temurin adds LTS support, TCK certification, and pre-built binaries tested across specific platforms. Upstream OpenJDK provides only the latest rolling release with six months of support and no long-term patch streams.
Is Temurin free to use in production?
Yes. Eclipse Temurin is free for production use under the GPLv2 with Classpath Exception license. There are no usage fees, royalties, or subscription requirements. This makes it a cost-effective alternative to Oracle Java SE, which has required paid subscriptions for production use since 2019.
Does OpenJDK have LTS versions?
No. The OpenJDK project itself does not maintain LTS versions. LTS is a concept introduced by distributions like Eclipse Temurin, Azul Zulu, and Amazon Corretto, which provide extended security patch backports for specific versions such as 8, 11, 17, and 21 beyond the standard six-month support window.
Which Java versions does Eclipse Temurin support?
Eclipse Temurin provides LTS builds for Java 8, 11, 17, 21, and 25, plus builds for current non-LTS releases. For broader version coverage including Java 6, 7, and versions through Java 25 and beyond, Azul Zulu offers the widest range of supported Java versions among free OpenJDK distributions.
What is the difference between Temurin and Azul Zulu?
Both are free, TCK-certified OpenJDK distributions, but Zulu supports more Java versions (6 through 25+) and more operating systems including Alpine Linux musl builds. Azul Zulu also provides a commercial upgrade path to Azul Core for enterprises that need SLA-backed support and dedicated engineering, while Temurin offers only community-level support.
Conclusion
Eclipse Temurin is an excellent, production-ready OpenJDK distribution that solves the core problem of vanilla OpenJDK: lack of LTS support and TCK certification. For standard server and desktop platforms, Temurin is a reliable free choice. However, teams that need broader platform coverage, a wider Java version range, or commercial support options will find Azul Zulu and Azul Core a more complete solution.
Azul Zulu covers Java 6 through 25 and beyond, supports Alpine Linux, Solaris, and many additional platforms, and provides a seamless upgrade path to Azul Core for enterprise SLA support. Both Zulu and Temurin are free, but Zulu gives you significantly more flexibility as your infrastructure and support needs grow.