Latest Release: Tcl/Tk 9.1.0 (Sep 29, 2026)

Tcl/Tk 9.1.0 is the current development work on Tcl and Tk, aiming toward stable releases in September 2026. They add new features and interfaces to the foundation of Tcl/Tk 9.0.

Download Tcl/Tk 9.1.0 Source Releases

Highlights of Tcl 9.1

New command unicode : Unicode normalization

New C routines Tcl_UtfToNormalized* : Unicode normalization

New command timer : monotonic clock; microsecond resolution

New command lfilter : select items from list

New command interp set : variable access in child interpreter

New subst options: -backslashes , -commands , -variables .

New switch options: -integer .

Many C99 math routines now available as expr functions.

Applications now required to call an initialization routine, either Tcl_FindExecutable or TclZipfs_AppHook .

New C routine Tcl_IsEmpty .

New C routine Tcl_GetEncodingNameForUser .

New C routine Tcl_AttemptCreateHashEntry .

New C routines Tcl_ListObjRange , Tcl_ListObjRepeat , Tcl_ListObjReverse .

New C…