The short version: Some dupes, like TNT, carpet and rail duplication, are still in vanilla Java because the technical community relies on them. Paper turns them off by default. Other dupes are real exploits that ruin server economies, and 2026 saw several viral videos aimed squarely at pay-to-win servers. The best defence is an up-to-date server, Paper’s defaults, a preventive anti-dupe plugin and logging that lets you roll back.
Two kinds of dupes
| Technical dupes | Exploit dupes | |
|---|---|---|
| Examples | TNT, carpet and rail duplicators | Inventory, disconnect, shulker, mount or bundle tricks |
| Status in vanilla Java | Still present; Mojang has left them alone because there’s no replacement for what they power | Fixed whenever Mojang patches them, but new ones keep appearing |
| Used for | Tunnel bores, world eaters, carpet-fuelled furnaces | Flooding economies with rare items or currency |
| Who cares most | Technical players and SMPs | Servers that sell items or ranks |
Players have been asking Mojang to replace TNT duplication with a legitimate mechanic for years. As of the 26.x updates, it still works in vanilla Java.
Why pay-to-win servers are the target
When a server sells items, every duplicated one undercuts the store. That makes heavily monetised servers the favourite target of dupe hunters, and in 2026 it became content:
- June 2026: Rediscover Redstone published a video showing simple duplication methods for current Java and Bedrock versions, tagged openly at pay-to-win servers.
- August 2026: YouTubers zman1064 and LowkMethod posted footage of duping a heavily monetised Cobblemon server, the latest in a series aimed at modded pay-to-win servers.
Whatever you think of the targets, the lesson for any server with an economy is the same: assume a dupe exists, and make sure you can detect it and undo it.
How Paper handles vanilla dupes
Paper fixes the vanilla duplication bugs by default. Owners who want them back can opt in through config/paper-global.yml under unsupported-settings:
| Setting | Restores |
|---|---|
allow-piston-duplication: true |
TNT, carpet and rail duplication |
allow-unsafe-end-portal-teleportation: true |
Gravity block (sand, gravel) duplication through end portals |
skip-tripwire-hook-placement-validation: true |
Tripwire hook duplication |
Paper doesn’t support servers that have these enabled, so technical SMPs that turn them on are on their own if something breaks.
Anti-dupe plugins: what they do
- Preventive plugins such as ExploitShield (Spigot) and the free MultiProtect block known patterns like piston, hopper, anvil, shulker and mount dupes. ExploitShield’s 6.1 update in October 2026 reworked its inventory tracking to reduce false positives.
- Detective plugins such as DupeWatch fingerprint valuable items and flag copies. Reviewers point out they don’t stop a dupe, they only tell you it happened, so pair them with a preventive plugin and a rollback logger such as CoreProtect.
Checklist for server owners
- Run the latest server build for your version. Many dupes are fixed in Paper builds before or alongside Mojang’s own patches.
- Keep Paper’s dupe fixes on unless your community is built around technical play.
- Add a preventive anti-dupe plugin, and log item and container changes so you can roll back.
- Watch your economy for sudden price drops or item counts that jump. That’s usually the first sign of a dupe.
- Patch fast and say so publicly. Players forgive a dupe more easily than a cover-up.
