Leaning Technologies today released CheerpJ 4.1, the latest version of its WebAssembly-based Java runtime for the browser. The release includes a preview of Java 17 support, several months ahead of the company’s published roadmap.

CheerpJ runs Java applications, applets and Java Web Start applications in modern browsers, with no Java installation, plugin or server-side component. CheerpJ 4.0, released in April 2025, was the first version to support both Java 8 and Java 11.

What CheerpJ 4.1 adds

  • A preview of Java 17, ahead of stable support planned for CheerpJ 5.0
  • SSL and audio support for Java 11 applications
  • An improved networking stack and performance optimisations
  • Better mobile usability for Swing and AWT applications, on phones and tablets
  • Stability fixes for Java 11, found through testing by the developer community

The full announcement is on the CheerpJ blog, and the technical release notes are on Leaning Technologies’ technical blog.

About Leaning Technologies

Leaning Technologies is a world-renowned developer of WebAssembly technologies and the creator of CheerpJ, a Java Runtime for the Web that allows organisations to run and modernise Java applications directly in modern browsers — without plugins, installations, or code rewrites.

Learn more: https://cheerpj.com