The Headless Master Chief is a glitch that can be seen at the beginning of the Halo: Combat Evolved campaign level Pillar of Autumn. The glitch causes a headless John-117 to appear inside of a cryo-tube.
- Wait until John steps out of the Cryo-chamber.
- A split second after you come out, jump back inside the cryo tube.
- You should then see the Headless Master Chief.
Another way is to crouch jump into the cryo-chamber (see video); this way, you will not need to look at a certain angle—you will see the oddity front on. The only downside about this is that once the lid on the cryo-tube has closed, you are stuck inside it, and you will have to restart the level to continue, though sometimes, jumping inside the cryo-chamber can fling you out and let you continue the game or you will be pushed out of the level and fall through the ground and die.
In Halo, a player's body is hidden while in first-person view. When the level starts, though, the player can still see their own body while in first-person view. This is because the player is actually in third-person view—the camera has simply been positioned in the same location it would be in in first-person view. Bungie effectively simulated one view mode with another.
However, simply moving the third-person camera inside John-117's head would cause problems. Backface culling would make much of the head invisible, but some chunks of the head would still be visible (and would render somewhat oddly). This is particularly noticeable with the two prongs at the top of a Spartan's helmet. Bungie avoided this undesirable visual effect by simply removing (or moving) John-117's head during the scene where the HUD is first activated.
Forcing John-117 back into the cryo-pod simply restores this state—these effects (third-person point of view, invisible head, etc.) are all applied whenever John is in the cryo-pod, since (without the involvement of glitches) he is only in the pod before the cutscene where he exits.