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The JRE provides the Java runtime needed to run Java applications; the JDK adds tools for developing, compiling, testing, and monitoring Java software. If you write or build Java code, choose a JDK. If you only run an existing application, use the Java version and distribution that its publisher specifies.
What is the difference between a JDK and a JRE?
| Aspect | JRE | JDK |
|---|---|---|
| Main purpose | Run Java applications. | Develop, compile, test, and monitor Java programs. |
| What it provides | The Java virtual machine (JVM), libraries, and other runtime components. | Runtime capabilities plus development tools, including the Java compiler and debugger tools. |
| Current packaging caveat | A separate JRE image is not part of JDK 11 and later, according to Oracle’s migration guide. | Do not assume a current JDK installation contains a separate jre/ folder. |
Oracle describes the JRE as the components needed to run Java applications and the JDK as the development environment with tools such as compilers and debuggers. See Oracle’s Java SE Technologies overview and the JDK 25 readme.
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Which one do you need?
Choose a JDK if you write or build Java software
Install a JDK if you are learning Java, editing a project, compiling source code, running development tests, or monitoring a Java program. Its tools include javac, the Java compiler. Oracle describes the JDK as a development environment for building applications and components, with tools for developing, testing, and monitoring Java programs.
Running an existing application? Follow its requirements
If you only launch a Java application, check that application’s documentation for its required Java version and vendor or distribution. Do not assume the newest Java release will work with every older application; compatibility is application-specific. A standalone JRE download is not the only way to get the runtime, and for JDK 11 and later Oracle says there is no separate JRE image in the JDK installation. The Oracle JDK 26 Migration Guide states that “JDK 11 and later does not have the JRE image.”
Packaging an application? Consider the deployment requirements
Oracle lists jlink among JDK tools for creating runtime images. Whether that is the right packaging approach depends on your application’s distribution and deployment needs; it is not required just because you are writing Java code.
Why do older guides say the JDK contains the JRE?
That shorthand describes the functional relationship: the JDK provides what is needed to run Java programs as well as tools to develop them. It can mislead when read as a promise that a modern JDK contains a separately installable JRE or a jre/ directory. Oracle’s migration guide identifies JDK 11 and later as having no separate JRE image, so use the current packaging documentation for your chosen vendor and version rather than relying on an old folder layout.
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Does the latest Java version change the choice?
No. “Latest release” and “latest LTS” describe release status, not whether you need runtime or development tools. As of October 7, 2026, Oracle’s downloads page lists JDK 27 as the latest Java SE release, JDK 25 as the latest Long-Term Support (LTS) release, and JDK 21 as the previous LTS. Those labels can change; check Oracle’s Java downloads page for the current list, then check your application or project for its required version.
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1Fix the driver behind crashes, sound loss and screen glitches2Repair Windows errors before they cause bigger problems3Scan for outdated or missing drivers - takes under a minuteFor a dated update example, Oracle’s release notes identify JDK 25.0.4+7 as released on July 21, 2026. That is an update-level fact, not a recommendation that every user install that version. See Oracle’s JDK 25.0.4 release notes.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Do JDK and JRE licensing differ?
There is no universal answer that “Java is free” or that “Java requires a paid license.” Terms vary by vendor, product, version, and update. Oracle’s licensing FAQ, updated September 16, 2025, distinguishes Oracle JDK and Oracle OpenJDK terms by release; for example, it describes Oracle JDK 21 and later under Oracle No-Fee Terms and Conditions while treating older releases differently. Check the terms for the exact distribution and version you plan to use in Oracle’s JDK License General FAQs.
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