Portal Dupe (fixed).

Portal Dupe is a dupe that works in Minecraft Beta 1.7.3. It previously worked in 2Beta2T but has since been fixed.

You can see an example of the dupe process here.

The dupe involves creating a stream of water leading to a Nether portal, placing a crafting table nearby, and then standing in the stream. Then, place the item you want to dupe in the crafting table and swim in the stream of water to the end of the portal.

The item will create a duplicate of itself. The dupe station looks like this (screenshot from 2Beta2T):

Dupe station near spawn..
Screenshot from the April Fools' Day 2025 update.

The exact coordinates of this place are: -290 68 -567.