The Portal is part of the October 31st Halloween Update. It consists of a frame of Obsidian, four blocks wide, by five blocks tall. The corners of the frame are not required, and only serve for aesthetic purposes. Once the frame is constructed, the player then sets the space inside the frame on fire, using a flint and steel. This creates 6 portal blocks inside the frame, resembling a vortex. Here is a diagram of the process:
The usual way to build a portal. (Left)
The economy version of a portal with no corners. (Right)
When the player stands in a portal block for a few seconds, the player is taken to The Nether. The player can step out of a portal before it completes its animation to abort the teleport. A portal will also be created in the place where you enter The Nether, which you can again enter to be returned to the normal world. Building multiple portals on Earth within a certain proximity will all lead to the same portal in The Nether, and the same might happen vice versa.
The purple portal blocks emit light, so passive mobs may crowd around active portals at night. Like Bedrock, portal blocks cannot be broken (although they can disappear); however, they can be placed with modding. These portal blocks will automatically disappear after a few seconds, or when a block is placed adjacent to it. The only exception is to place an obsidian block, and a portal piece next to that. The portal piece will disappear once the obsidian block is gone. However, portal blocks will not disappear in SMP.
Portals can deactivate if there is fire adjacent to it (started by the player or Ghasts). TNT can also disable a portal, but cannot destroy the surrounding Obsidian. It is possible to "re-ignite" portals by setting the space inside the frame on fire once again.
Contrary to public belief, portals do not conserve momentum.
It has been confirmed that portals do not work in multiplayer yet; while they can be created, they can not teleport you. Server settings can be changed in order to visit The Nether in multiplayer[1].
Notch has mentioned it is extremely unlikely, but possible, for Ghasts to appear on Earth near a portal.
Media
- Here and here are two preparation videos with commentary, in which people craft portals according to Notch's specifications.
- On 10 October 2010, Notch revealed the above screenshot on his blog showing portals.
- On 29 October 2010 PC Gamer released this video, showing a portal being constructed and used.