While players are not actually able to turn invisible, they do have the ability to sneak up on a non-player target, or at least attempt to. This works well for creatures like pigs or stag in order to get a better shot before they see you and run. Crouching also makes a player slightly less detectable.
This also works on zombies. To use stealth, push and hold the crouch key (default key C on PC), or use Left Ctrl to toggle crouch mode. The crosshair will become an eye symbol and show whether or not the player is detected, hidden or sensed.
While crouched, certain actions are performed slower and quieter. For example, doors and storage are opened slower but quieter.
Zombies investigate sounds near them. Therefore, an item such as a Small Stone can be thrown to try to distract the zombie. Different actions have different noise levels. For example, a Chainsaw is louder than a Stone Axe and can more easily attract zombies.
Zombies used to be able to detect you by smell when carrying raw meat or cooked food. However this was taken out because it was not working properly. Once it is reworked it may make it back into the game
When a character is carrying something that smells, the Emitting Smell buff is activated and the smell icon25px becomes visible in the bottom-left corner of the screen as well as in the Character Menu.