Built on the Hundred-Kilobyte Kernel (HK2) , it offers a modular, OSGi-based core that is both extensible and fast to start. System Requirements & Prerequisites

While newer versions like GlassFish 7 and 8 support modern Jakarta EE 10/11 standards and Java 17+, GlassFish 5.1 remains the definitive open-source baseline for .

It was the "proof of concept" that the entire GlassFish codebase could be successfully built, tested, and released by the Eclipse community using the Eclipse Development Process .

For developers, downloading and using GlassFish 5.1 is primarily about maintaining or exploring applications in a pure open-source environment. Below is a comprehensive guide to its features, system requirements, and how to download and install it. Why Download Eclipse GlassFish 5.1?

It is fully certified for Java EE 8, including support for JSON-B 1.0, CDI 2.0, and HTTP/2.

represents a historic turning point for enterprise Java. Released in early 2019, it was the first version of the venerable GlassFish application server produced entirely under the Eclipse Foundation after the transfer of Java EE from Oracle.