Tom Clancyвђ™s Rainbow Six Siege-codex -

Because the game relies on official Ubisoft servers for its 5v5 tactical matches, cracked versions cannot access online multiplayer.

refers to a specific "scene release" of the game created by the group CODEX . In the world of PC gaming, this version represents a cracked copy of the game designed to bypass Digital Rights Management (DRM) and allow the game to be played without a legitimate license or an internet connection. What is "CODEX"? Tom Clancy’s Rainbow Six Siege-CODEX

The release removes requirements for platforms like Ubisoft Connect (formerly Uplay) or Steam. Because the game relies on official Ubisoft servers