Glass etching with cnc

Some folks have used a regular carbide endmill (this has safety implications and is best done with the glass submerged):

https://www.reddit.com/r/CNC/comments/cijwu8/milling_a_1x1_cm_glass_square/

Note that the debris from cutting must be discarded in a safe fashion and not poured into a municipal water system (the tiny shards will shred the filters).

Otherwise, a diamond drag bit is the usual choice: