Java 27 Is Out: Post-Quantum TLS and G1 by Default

On September 15, 2026, JDK 27 reached the General Availability stage. It is the reference implementation of version 27 of the Java SE platform, as defined by the JSR 402 specification within the Java Community Process. Production-ready builds under the GPL license are already available from Oracle; binaries from other vendors will appear shortly.

What's New

Among the changes that made it into the release as permanent features are the promotion of the G1 garbage collector to the default in all environments (JEP 523) and the enabling of compact object headers by default (JEP 534), which should reduce memory overhead. Deserving special attention is the hybrid post-quantum key exchange for TLS 1.3 (JEP 527) — a step toward cryptography resistant to attacks from quantum computers. Rounding out the data-protection picture are the ability to redact sensitive information on the fly in the Java Flight Recorder (JEP 536) and support for PEM encoding of cryptographic objects, still in its third preview (JEP 538).

Long-Running Previews and Incubators

A significant share of the new features are still being road-tested. Work on primitive types in patterns, instanceof, and switch has reached its fifth preview (JEP 532), structured concurrency (Structured Concurrency) is already at its seventh (JEP 533), and lazy constants are presented in a third preview (JEP 531). The Vector API, begun several years ago now, marks its twelfth run as an incubator (JEP 537) — something of a patience record for a mechanism that just can't seem to leave the preliminary road-testing stage.

The release schedule was kept to the classic OpenJDK pattern: the Rampdown One phase began on June 4, 2026, the second phase on July 16, the release-candidate stage started on August 6, and the final candidate build came out on August 20. The release was carried out under the standard JDK Release Process (JEP 3), using the updated JEP process version 2.0.

Source: Lobsters