Java Almanac
Ever needed to quickly check what changed between Java 17 and Java 21?
Wanted to grab the official API docs for an older JDK?
javaalmanac.io is the site to have in your bookmarks!
History
Created by Marc R. Hoffmann and maintained by the Java community, the Java Version Almanac is exactly what the name suggests: a systematic, well-organized collection of information about every Java version, from the pre-1.0 days all the way to the latest LTS and the versions currently in development.
For each release you get direct links to the API documentation, the Java Language Specification, the JVM Specification, and tool references. More useful still is the API diff feature: you can compare the API of any two versions side by side, which is invaluable when migrating a project or reviewing what was added, changed, or removed between releases.
Beyond the version table, the site covers Java bytecode, a catalog of language features per version, code snippets showcasing modern Java, and a references section. All structured data is also available via a public REST API if you want to build tooling on top of it.
Everything is open source, managed in a public GitHub repository, and published under Creative Commons BY-SA 4.0.
If you work with Java daily — or even occasionally — the Java Version Almanac is one of those quietly indispensable resources you'll find yourself reaching for more often than you expect.