The heads-up display or HUD appears on screen while the player is in the game. It is superimposed on his or her view of the game world.
The HUD consists of the user's health bar, hunger bar, experience bar, and hotbar, as well as a cross-hair that pinpoints where he or she is looking. The armor condition bar appears above the health bar if the player is wearing armor. The oxygen bar will display above the hunger bar if the player is underwater. Also, in multiplayer, chat is part of the HUD, in the bottom left corner, showing the last few things spoken. This can be expanded with T. The HUD also contains, if applicable, the unlicensed copy note. In the Options menu, GUI size changes the size of the HUD between "large" or "small". Small is only recommended for large or low-resoloution screens, and large is default.
Players can remove the HUD by pressing the F1 key on their keyboards (and pressing F1 again to show it). A detailed Debug screen can be added to the HUD by pressing F3, which shows details but clogs up the HUD. As of 1.2.4, a less detailed Debug screen can be added to the HUD by pressing ⇧ Shift+F3.
All elements of the HUD can be changed with texture packs
You cannot remove the HUD in Minecraft Pocket Edition.