Updated 25 October 2026. Facts on this page come from minecraft.wiki, community sites named in the text and the live Artemis PvP server; sources are listed at the bottom.
TNT Duplication (TNT Dupers)
TNT duplication is a game bug, documented for Java Edition, that lets a machine make primed TNT without using up the TNT block. Large 'TNT duping arrays' feed ender pearl cannons and long-range cannons. Because it is an exploit, it can be fixed at any time and is banned on many multiplayer servers.
What is a TNT duper?
minecraft.wiki's large-scale TNT duplication tutorial describes the goal: duplicate large amounts of TNT and move it all to one position before it explodes, so another machine can use it. Pearl cannons and long-range TNT cannons are its main users. The page carries a warning that it uses a bug that may be fixed without warning, and that bug exploits may be disallowed on servers and lead to a ban.
How does it work?
The common designs push a line of TNT into a coral fan. The fan's support block must move before any TNT is replaced by moving blocks, so the fan breaks and sends updates after the piston has listed the blocks to push but before the TNT is removed. The most common large-scale method:
- Start with powered redstone dust that is not powering the TNT.
- Redirect the dust so it powers the TNT without updating it (the TNT is 'budded').
- Push the line of TNT.
- Redirect the dust back before the TNT arrives, or it will be lit there.
The tutorial also covers budding with moving observers and powering dust from moving blocks, flat and vertically stacked layouts, and compression with slime bars, TNT or conveyors.
Why do cannons use dupers?
A duper gives an endless supply without hand-loading. minecraft.wiki's automatic cannon page lists duper cannons as at least partly automatic and common in Survival, with dispenser cannons as the alternative where duping is not allowed. See automatic and dispenser cannons and pearl cannons.
Is TNT duping allowed?
It depends on the server, and often it is not; minecraft.wiki says dispenser cannons are used wherever duping is not allowed. Bedrock Edition works differently: minecraft.wiki's missile page notes bombers can work on Java with TNT duplication or on Bedrock with an observer and dispenser. Check the rules where you play; on ArtemisPvP see the rules. Redstone basics: redstone basics.
Frequently asked questions
What is a TNT duper?
A machine that uses a Java Edition bug to make primed TNT without using up the TNT block.
Can you get banned for TNT duping?
On some servers, yes. minecraft.wiki warns bug exploits may be disallowed and lead to a ban.
Sources
Every fact on this page was checked against these pages; the wording is ours.