JDK 27 is out

The new Java release is live. OpenJDK made JDK 27 generally available on 15 September 2026. Oracle runs the project. It's free; the builds on jdk.java.net come under the GPL v2 with the Classpath Exception. The site currently carries the 27.0.1 update (for Linux x64, Linux AArch64, macOS AArch64 and Windows x64).

The release has nine JEPs (JDK Enhancement Proposals, that is, proposals for improving the JDK). Five of them are still in preview or incubation. The real change is in the defaults. Since JDK 9, machines with a single processor or less than 1792 MB of memory got the Serial garbage collector; now G1 is chosen everywhere. Compact object headers are also on out of the box, no flag needed: on 64-bit platforms the header drops from 96 bits to 64. According to the SPECjbb2015 measurements in the JEP, that saves up to 22 per cent of memory and up to 8 per cent of CPU time. In TLS 1.3 the post-quantum X25519MLKEM768 key exchange is now the default. Flight Recorder, for its part, hides values like passwords and tokens as "[REDACTED]" before the recording ever leaves the process.

Mind you, this is a short-support release. The long-term support (LTS) release is still JDK 25. Free updates will reportedly run until March 2027, when JDK 28 is due. If your servers are on JDK 25, there's no rush. But trying out the new defaults ahead of time is not a bad idea at all.