Minecraft wiki entry for Nether_Portal_(block), associated text: Nether portal blocks can be used to teleport entities between the Nether and the Overworld. When a player in the Overworld or the Nether stands in a nether portal block for 4 seconds, the player is taken to the other dimension. While in the nether portal block, the player can neither open their inventory nor interact with blocks with GUI. The player can step out of a portal before it completes its animation to abort the teleport. However, in Creative mode there is no wait time—the player immediately transfers between dimensions. If there is already an active portal within range (125 blocks) in the other world, the player appears in that portal. Otherwise, a portal is created at or near the corresponding coordinates. If a single portal block is placed using commands, it can still be used to travel to the Nether.