OpenJDK stands for Open Java Development Kit, which is a free and open-source implementation of the Java Platform, Standard Edition (Java SE) . It is the result of an effort Sun Microsystems began in 2006, and it is licensed under the GPL-2.0-only with a linking exception. OpenJDK is the official reference implementation of Java SE since version 7. Some notable components that fall under the OpenJDK project include the Java class library, the Java compiler, the Java Runtime Environment (JRE), and the Java virtual machine (JVM) .

OpenJDK is available for download and installation on Linux, macOS, and Windows. Oracle also offers commercially-licensed JDK 21 binaries based on the same code as OpenJDK. OpenJDK follows a strict, time-based model that is split into development branches and releases new features every six months. Companies such as Azul, Eclipse, IBM, Red Hat, Oracle, and SAP offer implementations of Java SE, while the OpenJDK Community includes academics, open-source operating system distribution developers, and individual software developers.

Red Hats build of OpenJDK is a free and open-source alternative to Oracle JDK, which allows organizations to stabilize and standardize their Java environments for years to come with little to no transition effort or traditional licensing hassles. Red Hat provides long-term support for OpenJDK versions 8, 11, and 17, and expects to deliver four updates per year for the OpenJDK 8, 11, and 17 distributions, in addition to timely security fixes.