To build a functional Nether portal in Minecraft, you need at least 10 obsidian blocks. This minimum frame is a vertical rectangular shape that is 4 blocks wide and 5 blocks tall, excluding the corners. The corners are optional and can be left out or filled with other blocks, which reduces the obsidian needed to 10 blocks instead of 14 if you include the corners. The portal frame is then activated by lighting it with flint and steel or another fire source, which fills the frame with a purple portal texture allowing travel to the Nether dimension
. Summary:
- Minimum obsidian blocks: 10 (without corners)
- With corners: 14 obsidian blocks
- Frame size: 4 wide × 5 tall (minimum)
- Activation: Flint and steel or other fire source
You can also build larger portals up to 23×23 blocks, but the basic portal requires only 10 obsidian blocks without corners
