Tutorials/Nether portals

The creation of nether portals can be used for a variety of different means. This page lists some of the implications of these portal mechanics.

First portals are risky
Portals try to avoid spawning over lava, in midair, or inside rock, but they do so by spawning nearby. Thus, a new portal from the Overworld has a disproportionate chance of being next to an abyss, lava lake, or netherrack wall. There is also no check as to whether a lava source (created with the landscape) is destined to send lava flowing over the portal. Furthermore, a portal can spawn on a one block thick ledge or floor, or on a Soul Sand outcrop.

Portals can accumulate Overworld mobs
Portals built in the Overworld should be secured from wandering hostile mobs. These creatures can accumulate over time while the player is spending much time nearby doing other things. Entering the portal and finding several Creepers on the other side can be disastrous, as Netherrack is very soft and a Creeper explosion can open vast holes leading to the Lava ocean.

Farming obsidian
See Tutorials/Obsidian farming.

Portals can be built in networks
No more than 64 Nether blocks (256 Overworld blocks) apart, in the manner reminiscent of the gates in the Stargate series. You should build portals at (this is the maximum ideal distance, but they can be built as close to 16 Overworld blocks apart, if the co-ordinates are accurate) 64 Nether block intervals, even if you are not normally going to use these gates. This is so that if you use Nether portals for long distance travel, and your usual Overworld destination portal becomes inaccessible for some reason, (due to large gravel caveins, lava, water, or you have an automated activation system and forgot to turn it on) you will still have a reasonably close backup gate, which will get you back into your gate network.

Likelihood of 2 overworld portals linking to the same Nether portal
Overworld portals that are within 1024 distance of each other on both X and Z axis are almost always going to link to the same Nether realm portal on initial construction because 1024 translates to a distance of 128 in the Nether Realm, and the game checks for existing Portals within 128 "radius" around the destination (the 257×257×128 box).

Pairing portals
To setup pairs of Nether portals properly so that they reliably travel to each other, it is best to build both portals manually. Build at desired location X,Y,Z in the Normal World. Then travel to the Nether World. And then dig your way to X/8, Y, Z/8, and build a portal there. A less precise method would be to temporarily deactivate all portals within a 128 block "radius" from within The Nether. Through death or with the aid of a second player, entering a new portal from the Normal World will force the creation of a new portal within the Nether which the Normal World portal should prefer. This is not recommended as it limits how close Normal World portals can be placed due to the Zone of exclusions and can lead to unpredictable placement of the resulting portal.

Zones of exclusion
The Nether portal spawning algorithm can only spawn portals that are within a 33×33 block column centered on the destination. This will often cause it to spawn a portal at a location significantly different than the corresponding location in the other world. The larger the distance between two linked portals, the larger the zone of exclusion. This zone is the area in each world where you cannot build another portal without breaking the link between the first two portals. One way to think of this zone is as spheres around each portal, each of a true radius equal to its distance to the other. For example, if the Normal world portal was at (0,50,0) and the Nether portal at (0,100,0), then each portal is 50 meters away from the other. In this (simple) case, if a Nether portal was built closer than 50 meters to (0,50,0), then the Normal World portal will now link to it. If you wish to ensure that two portals link together, manually build portals as close as possible in all 3 coordinate axes. It doesn't have to be exact, or even all that close, if the player ensures that no other portals will be constructed in the exclusion zone created by the difference.

1-way long distance teleport
The portal choosing algorithm can be used for long distance travel by manual construction at carefully selected coordinates. If the player has a Portal in Normal world at (0,64,0) but makes a Nether Portal at (127,64,127) with its perfect Normal World pair at (1016, 64, 1016), then the portal at (0,64,0) will go to the Nether Portal correctly (1-way trip) because it is the only portal available within the 128 search distance along X and Z horizontal axes of the expected Nether portal position of (0,64,0). In about 15 seconds, the player can then travel 1436 meters in the Normal World. This specific form of fast travel by Portal is one-way, since the Nether portal will not find this Normal World portal. Given that a railway in the nether would need to span only 180 meters to go this distance, it is usually not worth making such portal links. However, it is theoretically possible to make a one-way ring of portals, with each Normal World to Nether jump going a long distance, but such a ring would easily be disrupted due to the huge exclusion zones created.

Non-exploit water ladder replacement
The Nether Portal is an also entirely viable, two-way replacement for the water or conventional ladder. Note that if you want to travel a vertical distance of h from a point (X, Y, Z) in the Overworld to (8*X, Y+h, 8*Z) in the Nether, there must be no other Overworld portal within a distance of 8*h from (X, Y, Z) (i.e. (X/8)² + (Y/1)² + (Z/8)² = h², note that Y is not divided by 8). That is, if you want to travel large vertical distances, there must be no horizontally close portal. (This holds for a portal from the Overworld to the Nether. The reverse direction (Nether to Overworld) was not discussed here.)

2-in-1 Nether Portals
It is possible to end up in a situation where a Nether Portal "randomly" places the player in 1 of 2 possible Normal World destination portals. This is simply because the Nether Portal has two effective coordinates as it is 2 blocks wide, say (X, Y, Z) on the left, and (X+1, Y, Z) on the right. If the player entered on the left side, (X, Y, Z) translates to (X*8, Y, Z*8) in the overworld and the game picks the portal closest to that. If the player entered on the right side, (X+1, Y, Z) translates to (X*8+8, Y, Z*8) and the game picks a portal closest to that point instead. This situation occurs when the Nether Portal's location is roughly equidistant between the 2 Normal World portals (within 8 blocks overworld distance difference). However, building 2 Nether Portals side by side is probably better for destination clarity than building a 2-in-1 portal. It is possible to span distances with pairs of portals in this way, though normally faster to simply walk through the Nether.

Spawning a portal in the air
It is possible for a destination portal (either in the Nether or in the Overworld) to spawn floating in the air. If your portal spawns in the air, it will generate a 1×2×1 obsidian platform in the front and back of the portal. This can only occur if there is no possible spawn location in the entire 33×33×128 column of search region to find a suitable spot to place a fresh new portal AND there are no existing portals within the 128 block "radius" to link to.

Structure finder
With some luck, making a portal underground, entering the Nether and making another portal out of the other's proximity may create a portal in a stronghold, a cavern or even an abandoned mine shaft, all of which may contain a variety of rare minerals. (even diamonds, but the starting portal must be built under layer 16.)