How to Make a Fermented Spider Eye in Minecraft

Guide Java Bedrock

Quick answer: Craft it shapelessly from 1 spider eye, 1 brown mushroom and 1 sugar placed anywhere in the crafting grid. Fermented spider eyes brew Potions of Weakness, Harming, Slowness and Invisibility by corrupting other potions.

What you need

1 spider eye (spider or cave spider drop)
1 brown mushroom
1 sugar (from sugar cane)
Crafting grid (2x2 is enough; the recipe is shapeless)

Step by step

Kill spiders (or cave spiders) at night or in dark places until one drops a spider eye. Witches also drop them occasionally.
Get a brown mushroom: they grow in dark areas like swamps, caves, old growth taiga and the Nether, and you can shear a brown mooshroom for 5 of them.
Craft sugar from sugar cane (1 cane = 1 sugar) at a crafting table or in your 2x2 inventory grid.
Place the spider eye, brown mushroom and sugar anywhere in the crafting grid; the recipe is shapeless, so order does not matter.
Collect the fermented spider eye. It is not edible; its only use is brewing.
Use it in a brewing stand to corrupt potions: a Potion of Poison becomes Harming, Swiftness or Leaping becomes Slowness, Night Vision becomes Invisibility, and it brews a Potion of Weakness directly from a water bottle.

Java vs Bedrock

The recipe and brewing uses are the same in Java and Bedrock. In both editions the fermented spider eye is the only way to brew a Potion of Weakness without finding one, which makes it essential for curing zombie villagers.

Versions: 1.0 (added with the brewing system)

Frequently asked questions

What does a fermented spider eye do in Minecraft?

It corrupts potions in a brewing stand. Poison becomes Harming, Swiftness and Leaping become Slowness, Healing becomes Harming, Night Vision becomes Invisibility, and a plain water bottle becomes a Potion of Weakness.

Can you eat a fermented spider eye?

No. Unlike a regular spider eye, it cannot be eaten at all. Its only purpose is brewing.

How do you get a brown mushroom?

Brown mushrooms generate in dark spots: swamps, caves, old growth taiga, mushroom fields, and everywhere in the Nether. Shearing a brown mooshroom gives 5 brown mushrooms.

Do you need a fermented spider eye to cure a zombie villager?

Yes, in practice: curing requires a Splash Potion of Weakness plus a golden apple, and brewing Weakness from a water bottle needs a fermented spider eye (no blaze powder required for that one).