Files with grt extension are used by MegaHAL software. They are used for some various data used for internal purposes.
There is one other file type using
the GRT file extension!
.grt - Karmen HiddenTear (variant) ransomware affected file
GRT file extension - MegaHAL greeting file
What is grt file? How to open grt files?
File type specification:
The grt file extension is associated with MegaHAL, computer program which responds in natural language to what you type, written by Jason Hutchens. It is used for some various data used for internal purposes.