The JDK 21 Updates project uses two GitHub repositories. Updates are continuously developed in the repository jdk21u-dev. This is the repository usually targeted by contributors. The jdk21u repository is used for rampdown of the update releases of jdk21u and only accepts critical changes that must make the next release during rampdown. (You probably do not want to target jdk21u).

For more OpenJDK 21 updates specific information such as timelines and contribution guidelines see the project wiki page.

For build instructions please see the online documentation, or either of these files:

• doc/building.html (html version)
• doc/building.md (markdown version)

See https://openjdk.org/ for more information about the OpenJDK Community and the JDK and see https://bugs.openjdk.org for JDK issue tracking.