Azul vs Amazon Corretto vs Eclipse Temurin: OpenJDK compared

When an organisation decides to stop paying Oracle for Java, the next question is immediate and practical: which free distribution replaces it? Three names dominate the shortlist — Azul Zulu, Amazon Corretto, and Eclipse Temurin. All three are builds of OpenJDK, all three are free to run in production, and all three are genuine, supported exits from the Oracle Java SE subscription. They are not, however, identical. This guide compares them from a buyer’s and licensing perspective, so you can choose the right one for your environment rather than the first one a search engine returns.

What all three have in common

Before the differences, the common ground — because the common ground is what makes any of them a valid Oracle alternative. Azul Zulu, Amazon Corretto, and Eclipse Temurin are all distributions built from the OpenJDK source code, the open-source reference implementation of the Java SE platform that Oracle itself builds its commercial JDK from. The OpenJDK source is licensed under the GPLv2 with Classpath Exception, which permits free use, including in commercial production, without a per-employee fee and without a subscription.

That single fact is the heart of the matter. For the vast majority of workloads, a current OpenJDK build from any of these three vendors is functionally equivalent to Oracle’s JDK — same language, same APIs, same bytecode, same behaviour — while carrying none of Oracle’s commercial licensing. All three pass the Java SE Technology Compatibility Kit, meaning they are verified-compatible Java implementations, not approximations. All three publish builds for current and Long-Term Support releases, and all three are free to download and run. The choice between them is therefore not a choice about whether you can leave Oracle — you can — but about which vendor’s release cadence, support model, and platform fit suit you best.

Eclipse Temurin

Eclipse Temurin is the OpenJDK distribution produced by the Adoptium project under the Eclipse Foundation. It is the direct successor to the widely used AdoptOpenJDK builds, and it is, in spirit, the vendor-neutral community option — not owned by any single commercial company, but governed by a foundation with backing from many.

For enterprises, Temurin’s appeal is precisely that neutrality. Choosing it does not tie your runtime to a cloud provider or a commercial JDK vendor. It produces builds for the major operating systems and architectures, covers current and LTS releases, and is one of the most widely deployed OpenJDK distributions in the world — which means broad community familiarity and a low chance of surprises. Temurin itself is free and carries no paid support tier from the Eclipse Foundation; if you want commercial support contracts, those are available from third parties that support Temurin builds. For organisations whose priority is independence — leaving Oracle without simply becoming dependent on another single vendor — Temurin is often the natural default. Our dedicated comparison, Eclipse Temurin vs Oracle Java, covers it in more depth.

Amazon Corretto

Amazon Corretto is the OpenJDK distribution built and maintained by Amazon. Amazon runs Java at enormous scale internally and produces Corretto as the build it uses itself, then publishes it free for everyone. Its defining characteristic is tight alignment with the AWS ecosystem — it is the default and best-tested JDK across AWS services, container images, and Lambda runtimes — while remaining a perfectly general-purpose JDK that runs anywhere, on any cloud or on-premises.

Corretto is free, including the support that comes with it: Amazon provides no-cost long-term support, quarterly security and bug-fix updates, and back-ported patches for the LTS releases it covers, with no separate paid contract required. For an organisation that runs a significant footprint on AWS, Corretto is the path of least resistance — the JDK is already present, already tested against the platform, and already patched on Amazon’s schedule. It is equally valid off AWS; the alignment is a bonus, not a lock-in. The trade-off to be aware of is the same one as with any single-vendor distribution: your runtime cadence follows Amazon’s decisions. For most enterprises that is a low risk, given Amazon’s own dependence on Java.

Azul Zulu

Azul Zulu is the OpenJDK distribution from Azul, a company whose entire business is Java runtimes. Zulu Community builds are free OpenJDK distributions in the same mould as Temurin and Corretto — TCK-verified, covering current and LTS releases, free to run in production. Where Azul differs is that it is a specialist Java vendor with a deep commercial offering layered on top of the free builds.

That commercial layer is the reason many enterprises look at Azul specifically. Azul sells paid support subscriptions with defined SLAs, extended support that keeps older Java versions patched for longer than the community typically maintains them, and a separate high-performance runtime aimed at latency-sensitive workloads. For an organisation that wants a free OpenJDK runtime and a single commercial vendor to call when something goes wrong — or that runs older Java versions it cannot quickly upgrade and needs continued security patches — Azul is the most complete option. The free Zulu Community build alone is a fully valid Oracle replacement; the paid tiers are there if and when you want them. Our dedicated piece, Azul Zulu vs Oracle Java, expands on this.

Side-by-side comparison

How to choose

The good news is that there is no wrong answer among the three — each is a legitimate, free, fully compatible Oracle replacement. The choice is about fit, and three questions resolve it for most organisations.

First: do you want vendor neutrality? If a priority of leaving Oracle is to avoid being dependent on any single commercial vendor for your runtime, Eclipse Temurin is the clearest expression of that — foundation-governed, not owned by one company. Many enterprises choose Temurin for this reason alone.

Second: where do your workloads run? If a large share of your estate runs on AWS, Amazon Corretto removes friction — it is already the tested default across AWS services and comes with free long-term support and patches. The alignment is real and worth taking.

Third: do you need a commercial support relationship or extended version support? If your organisation requires a vendor with contractual SLAs to call, or if you run older Java versions that need continued security patching beyond the usual community window, Azul’s paid tiers make it the most complete option — while the free Zulu Community build remains available if your needs change.

A practical default for an enterprise with no strong steer from those questions is Temurin for general server and desktop workloads, Corretto where the workload sits in AWS, and Azul where a support contract or extended version coverage is a genuine requirement. The decision should be made deliberately and documented — not because the licensing demands it, but because a recorded rationale is what keeps your Java inventory coherent over time.

Can you mix distributions?

Yes — and many large estates end up doing exactly that. Because all three are TCK-verified OpenJDK builds of the same Java SE version, an application compiled and tested against one will, in the overwhelming majority of cases, run identically on another. There is no licensing barrier to running Temurin on your on-premises servers, Corretto on your AWS workloads, and Azul where you hold a support contract. None of these requires an Oracle licence, and none conflicts with the others.

That said, a deliberate mix is fine; an accidental mix is not. The risk in a large environment is not that distributions conflict technically — they rarely do — but that nobody knows which distribution runs where. An unmanaged sprawl of JDKs is how an Oracle binary slips back in unnoticed and creates exposure. The discipline, whether you standardise on one distribution or run a planned mix, is to record the vendor and version of every Java install and to govern how new ones appear. Our guide to tracking Java across the enterprise covers keeping that picture accurate.

Migrating off Oracle Java

Selecting a distribution is step one of perhaps eight. A real migration off the Oracle Java SE subscription runs roughly as follows: build a complete inventory of every Java instance and its current vendor; separate Oracle binaries from any OpenJDK already present; choose target distributions by workload; test applications against the chosen builds; roll out the replacement runtimes in a controlled sequence; remove the Oracle binaries; confirm none remain; and then govern the environment so they do not return.

The testing step is where attention pays off. The functional equivalence of OpenJDK builds means most applications simply work, but the responsible approach is to verify rather than assume — particularly for anything sensitive to garbage collection behaviour, anything bundling its own JDK, or anything with a vendor support statement that names a specific JDK. Our Java migration testing strategy and migration cost analysis cover the practicalities. The headline, though, is consistent: for enterprises that complete the move, the Oracle Java SE subscription cost — often six or seven figures annually under the employee metric — goes to zero, while the runtime keeps receiving security patches from a free distribution.

Getting independent help

Azul Zulu, Amazon Corretto, and Eclipse Temurin are all legitimate, free, fully compatible ways out of the Oracle Java SE subscription. The distribution you pick matters less than the discipline with which you migrate — a complete inventory, deliberate per-workload choices, real testing, a clean removal of Oracle binaries, and governance afterward.

Independent, buyer-side advisers bring exactly that discipline, with no Oracle partnership and no distribution vendor shaping the recommendation. Across 340+ Java engagements, that approach has helped enterprises move off Oracle Java cleanly — contributing to more than $180M in client savings and, where audits arose during the transition, a 68% average claim reduction. Our Java Migration service plans and runs the move to OpenJDK, our Compliance Assessment builds the inventory it starts from, and our Audit Defence service, backed by a money-back guarantee, defends a Java audit if Oracle raises one.

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