First, a reality check: There is no official .g5 extension in the JPEG standard. In the context of the "Sad Satan" rabbit hole (the infamous, likely fabricated dark web game from 2015), these files are usually:
In the various versions of Sad Satan that circulated on 4chan and the deep web, files named through g5.jpg were used as "jump scare" or ambient assets. sad satan g5jpg fix