Latest Release: Tcl/Tk 9.0.2 released on Jul 2, 2025. It's the latest major release with many new capabilities and some incompatibilities with Tcl/Tk 8.

• Tcl Highlights: 64-bit capacity (data values > 2Gb), Unicode and encodings (full codepoint range, new encodings), Zip filesystems (mount zipfiles as filesystems), Attached archives (enable app deployment), New notifiers (based on epoll or kqueue), Many new commands and features.
• Important Incompatibilities in Tcl: Namespace varname resolution (current namespace), I/O malencoding (raises error by default), Tilde (~) in pathnames (no longer home dir), tcl_precision no longer affects number formatting.
• Summary of Tcl Changes: Major features include 64-bit capacity, string length flexibility, internationalization, Zip filesystems, Unix notifiers. Notable incompatibilities involve namespace resolution, build options, I/O behavior, etc. New commands like array default, clock add weekdays, etc. are added.

Tk Highlights: Access to OS facilities (notifications, print, tray), Scalable Vector Graphics (partial support in images), Images (full access to metadata and alpha channel), Platform Features and Conventions improvements (two-finger gesture support).

• Summary of Tk Changes: Many improvements to use of platform features, new commands like tk sysnotify, widget options updated (e.g. new ttk::progressbar option), improved widget appearance (ttk::notebook with nondefault tab positions), partial SVG support in images.