This extremely simple mod introduces a single command that allows you to make yourself or another player invisible (both the player itself and the nametag). While you are in vanish mod, a simple text HUD will be shown above the hotbar with a notice that you are currently invisible to other players.

Usage:

/vanish: Toggle invisibility for yourself
/vanish <name>: Toggle invisibility for another player

Note: The /vanish command requires the vanish privilege.