How to make a Nether portal in Minecraft with just 10 obsidian
The frame rules from the 26.3 code: 10 to 84 obsidian, what may sit inside, where it lights, how far each side searches, and the End portal's 12 eyes.
A Nether portal is a rectangle of obsidian with fire lit inside it. The game checks the frame in PortalShape, and reading that code answers most of the questions people ask about building one.
The frame
- Only obsidian counts. The frame is checked against the block tag
#minecraft:nether_portal_frame, which in 26.3 holds exactly one block:minecraft:obsidian. Crying obsidian does not work. - The opening must be 2 to 21 blocks wide and 3 to 21 blocks tall.
- The corners are never checked. The code looks for obsidian under each column, above each column and beside each row — never diagonally.
That makes the obsidian count 2 × width + 2 × height for the opening, plus 4 if you fill the corners for looks:
| opening | obsidian (no corners) | with corners |
|---|---|---|
| 2 × 3 (smallest) | 10 | 14 |
| 3 × 4 | 14 | 18 |
| 4 × 5 | 18 | 22 |
| 21 × 21 (largest) | 84 | 88 |
The opening has to be empty before you light it: air, fire or existing portal blocks only. A torch, a flower, water or a bit of grass inside the frame is enough to stop it lighting.
Getting obsidian without a diamond pickaxe
Obsidian can only be mined with a diamond or netherite pickaxe: its hardness is 50, which is about 9.4 seconds with an unenchanted diamond pickaxe. Without one, make it in place: water flowing onto a lava source turns that source into obsidian. Pour lava into a mould where each frame block goes, then cover it with water, one block at a time — the frame appears already standing, and nothing needs mining.
Lighting it
Any fire inside the frame lights it, so a flint and steel or a fire charge is the usual tool. The one restriction is the dimension: the code only forms a portal in the Overworld or the Nether. A frame built in the End will not light.
Stand in the purple blocks and you travel after 80 ticks (4 seconds) in Survival or Adventure, or instantly in Creative. Both are gamerules in 26.3 — players_nether_portal_default_delay and players_nether_portal_creative_delay — so a server can change them.
Where you come out
The Nether's coordinate_scale is 8, so your X and Z are divided by 8 going in and multiplied by 8 coming back. The game then looks for an existing portal near that point before it builds a new one, and the search is not the same size in both directions:
| travelling to | search area around the target | columns searched |
|---|---|---|
| the Nether | 16 blocks each way | 33 × 33 |
| the Overworld | 128 blocks each way | 257 × 257 |
Both searches cover the full height of the dimension, and the nearest portal wins. If nothing is found, the game builds a fresh 2 × 3 portal (with corners, 14 obsidian) near the target, adding an obsidian ledge to stand on if it has to place it in mid-air.
The asymmetry is why portals "link wrong" one way but not the other: a Nether portal only has to be within 16 blocks of the converted spot to be reused, while an Overworld portal is found from 128 blocks away.
The End portal cannot be built
An End portal only exists in a stronghold's portal room, as a ring of 12 End portal frames. The frames have no recipe and cannot be mined in Survival. Each one generates with an Eye of Ender already in it 10% of the time, so a ring averages 1.2 eyes, and 28% of rings start with none.
An Eye of Ender is one ender pearl and one blaze powder. Thrown to find the stronghold, each eye has a 1 in 5 chance of breaking, so bring more than twelve.
To place a Nether portal where it will link cleanly, the Nether Portal Calculator converts coordinates both ways and marks the 16 and 128-block search ranges on a scale map.