The basic structure: obsidian blocks in a frame

A Nether portal in Minecraft is a rectangular frame made of obsidian blocks that creates a doorway between the Overworld and the Nether dimension. The frame itself must be at least 4 blocks wide and 5 blocks tall on the inside — that is, the empty space you walk through. The obsidian forms the border around that opening, so the full structure is 6 blocks wide and 7 blocks tall when you count the frame.

You do not need to fill in all the corners or build a solid wall. Only the edges matter. A standard portal looks like a rectangle standing upright, with obsidian on all four sides of the opening. Once the frame is complete, you light it on fire using flint and steel or a fire charge, and the purple swirling texture fills the opening.

Key Takeaways

  • Obsidian is the only block that works for portal frames and must be mined with a diamond or netherite pickaxe.
  • The minimum frame size is 4 blocks wide by 5 blocks tall on the inside, creating a 6-by-7 structure when you count the obsidian border.
  • You activate the portal by lighting any block inside the frame on fire using flint and steel or a fire charge.
  • Portals work best in open spaces away from flammable blocks, since the fire spreads and can damage nearby wood or leaves.

Getting obsidian: mining and crafting

Obsidian forms naturally when water flows over lava source blocks. You can find it in the Overworld near lava lakes, in the Nether itself, and in the End dimension. To mine obsidian, you need a diamond pickaxe or better — a netherite pickaxe is stronger but takes longer to craft. A stone, iron, or wooden pickaxe will not break obsidian, no matter how long you wait.

If you do not have a diamond pickaxe yet, you can create obsidian by pouring water over a lava source block. Dig a small channel, place a lava source block at one end, and pour water down from above or from the side. The lava and water meet and turn into obsidian. This method is slower than mining natural obsidian but works early in the game when you have only stone tools.

You need at least 10 obsidian blocks for a minimum-size portal. Most players mine or craft 14 to 20 blocks to have extras for repairs or building a second portal in the Nether.

Building the frame step by step

Start by choosing a flat, open location away from wood, leaves, or other flammable blocks. Mark out a 6-by-7 space on the ground using blocks you can see easily — dirt or sand works well. This marks the full footprint including the obsidian frame.

Place obsidian blocks to form the four edges of your rectangle. The bottom row is 6 blocks wide. The left and right sides are each 7 blocks tall. The top row is 6 blocks wide. The corners are shared, so you are placing blocks in a hollow rectangle shape, not filling it in solid. Once the frame is complete, the opening in the middle should be exactly 4 blocks wide and 5 blocks tall.

Double-check that all four edges are complete and that no blocks are missing from the corners. A broken frame will not activate, even if only one block is missing.

Lighting the portal with flint and steel

Flint and steel is the most common way to activate a portal. You craft it by combining one iron ingot and one flint in a crafting table. Flint comes from mining gravel with a shovel — gravel drops flint about 10 percent of the time. Iron ingots come from smelting iron ore in a furnace.

Hold the flint and steel in your hand and right-click (or use your attack button) on any block inside the portal frame. A small flame appears, and the purple swirling texture fills the opening within a second or two. The fire does not spread to nearby blocks if you built in an open space, but it will catch wood or leaves on fire if they are too close.

If you do not have flint and steel, a fire charge also works. Fire charges are dropped by blazes in the Nether or crafted from blaze powder, charcoal, and gunpowder. Right-click the frame with a fire charge the same way you would with flint and steel.

Portal placement: Overworld versus Nether

Portals work in both dimensions. A portal you build in the Overworld creates a matching portal in the Nether when you step through — the game generates one automatically if it does not already exist. The two portals are linked by coordinates: a portal at Overworld position X=100, Z=100 connects to a Nether portal at roughly X=12.5, Z=12.5, because the Nether is 8 times smaller in scale.

If you want to control where your Nether portal appears, build it in the Nether yourself at the coordinates you want. Then when you return to the Overworld through that portal, you will arrive at the matching Overworld location. This is useful for setting up a safe base or connecting two specific locations.

Avoid building portals in dangerous areas like directly above lava or in the middle of a mob spawner. The Nether is much more hostile than the Overworld, so arriving in a safe, enclosed space is important.

Common mistakes and how to fix them

The most common mistake is building a frame that is too small. The opening must be at least 4 blocks wide and 5 blocks tall. If your portal does not activate, count the blocks carefully — you may have built a 3-by-4 opening by accident, which is too small.

Another mistake is using the wrong block. Only obsidian works for the frame. Blackstone, deepslate, or other dark blocks look similar but will not create a portal. If you light a non-obsidian frame on fire, the fire just burns and spreads normally.

If your portal frame is correct but will not light, make sure you are using flint and steel or a fire charge. A regular flint block or steel ingot will not work. Also check that you are right-clicking on a block inside the frame opening, not on the obsidian itself.

Frequently Asked Questions

Can I build a portal smaller than 4 by 5?

No. The minimum size is 4 blocks wide and 5 blocks tall on the inside. Smaller frames will not activate, even if they are made of obsidian and lit on fire. You can build larger portals — up to 23 by 23 — but they use more obsidian and do not offer any advantage.

What happens if I break the portal frame after it is lit?

The portal closes immediately and the purple texture disappears. You can rebuild the missing blocks and light it again. Breaking obsidian requires a diamond or netherite pickaxe, so it takes time, but the portal itself does not break permanently.

Do I need to build a portal in the Nether if I have one in the Overworld?

No. The game creates a Nether portal automatically when you step through an Overworld portal. However, building your own Nether portal at a specific location lets you control where you arrive in the Overworld when you return, which is useful for base building.

Can I move a portal to a different location?

You cannot move an existing portal, but you can build a new one elsewhere. Break the old frame by mining the obsidian blocks with a diamond pickaxe, then build a fresh frame in your new location and light it.