Deno 2.5 brings permission sets, WebSocket header support, new runtime API, and more

Deno version 2.5 has been released, delivering multiple developer-focused enhancements for this modern JavaScript runtime. The update introduces permission sets managed through the deno.json configuration file, making it easier to define and audit permissions in your projects. Complementing these changes, the new DENO_AUDIT_PERMISSIONS environment variable enables JSONL-based permission audit logging for improved transparency.

Alongside security improvements, Deno 2.5 overhauls the testing workflow by adding several new APIs to Deno.test, assisting with setup and teardown routines in individual test cases. The WebSocket implementation now supports specifying custom headers on connection initiation, giving developers expanded control over authentication and integration with external services.

Building on these platform updates, the release offers a powerful runtime API for bundling JavaScript or TypeScript, covering both client and server contexts. In addition, deno bundle now accepts HTML files as entrypoints, making the tool better suited for web-centric builds. For improved developer ergonomics, deno run invoked with no arguments now displays a list of available tasks and scripts, while new methods for stdout and stderr were added to Deno.ChildProcess streams.

Other updates include an upgrade to V8 version 14.0 and TypeScript 5.9.2, a significant overhaul of the Temporal API, and miscellaneous tweaks such as improved formatting, dependency management, Node.js enhancements, and performance gains.