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Repair common Windows errors and clear accumulated junk for a smoother, more stable PC - no reinstall needed.Free scan · no reinstallPaper does not treat TNT duplication and related vanilla exploits as supported server features. Since Paper 1.15.2, the underlying behaviours have been patched; a small set of opt-in keys under unsupported-settings can restore them, but Paper may remove those keys and will not support a server that becomes unstable after they are enabled. On a public server, the safest configuration is to leave them disabled and use a private, disposable test instance if you need to study compatibility.
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What the “TNT duping configuration” really is
There is no supported Paper gameplay switch called “TNT mode.” The settings administrators usually mean are exceptions in Paper’s global configuration. They re-enable behaviours that exist in vanilla Minecraft because of bugs or edge cases, but that Paper deliberately patched for server safety and consistency.
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1Repair Windows errors before they cause bigger problems2Scan for outdated or missing drivers - takes under a minute3Clear out junk files and repair common Windows errorsThose exceptions are grouped under unsupported-settings. The group covers more than TNT. Depending on the key, it can restore duplication of TNT, carpet, rails or gravity-affected blocks, or permit destruction of blocks intended to be permanent. Treat the group as a compatibility escape hatch, not as a performance, redstone or quality-of-life option.
The distinction matters on a multiplayer server. A private experiment affects only the operator’s test world. On a public server, duplicated explosives and blocks can alter an economy, bypass intended progression, damage builds and create support incidents for every player connected to the instance.
Where Paper stores these settings
Paper’s configuration layout changed in the 1.19 era. Modern installations use files in the server’s config directory, including paper-global.yml. Older installations may still use paper.yml. If paper.yml is absent on an older-looking setup, check for paper-global.yml; if both exist, use the file expected by the Paper build rather than copying settings between versions.
Line numbers are not stable. Builds add, remove and reorder options, so searching for the key name is safer than following a line-number tutorial. The relevant names are nested below unsupported-settings:
unsupported-settings:
allow-piston-duplication: ...
allow-unsafe-end-portal-teleportation: ...
allow-permanent-block-break-exploits: ...
allow-headless-pistons: ...The ellipses above are intentional: the exact value and even the presence of a key can vary by Paper version. Do not paste a block copied from a different release without checking that release’s documentation and generated configuration.
Flag reference
| Setting | Behaviour it is associated with | Default or status established here | Operational concern |
|---|---|---|---|
allow-piston-duplication |
Restores the piston-based TNT duplication exploit. The same underlying bug also covers carpet and rail duplication. | The current default was not verified; check the documentation for the exact Paper build. | Can create unlimited explosive power and duplicate building or transport materials, affecting both worlds and economies. |
allow-unsafe-end-portal-teleportation |
Allows sand and other gravity-block duplication through End portals. | The current default was not verified; Paper documentation describes the behaviour as unsafe. | Gravity-block floods can consume storage, damage terrain and produce large numbers of entities or falling blocks. |
allow-permanent-block-break-exploits |
Restores exploits used to break bedrock and End portal frames. | The current default was not verified. | Permanent-world structures can be opened or destroyed, undermining spawn, containment and map-integrity assumptions. |
allow-headless-pistons |
Allows headless pistons, a technique commonly used to break blocks intended to be permanent. | Default is documented as false. |
Combines with other redstone exploits to bypass protections and remove blocks that operators expect to remain. |
allow-piston-duplication is therefore broader than its name suggests. An administrator who wants only TNT duplication cannot assume that carpet and rail duplication will remain unavailable; they share the same underlying patched behaviour. Conversely, enabling one unrelated key does not automatically restore every exploit in the table. Each capability is controlled by its own setting, and the build’s current documentation is the authority for defaults and accepted values.
Why Paper patched these exploits
Paper’s issue history records patches for TNT duplication, carpet and rail duplication, bedrock and End portal-frame breaking, and gravity-block duplication in Paper 1.15.2 and later. The opt-in settings exist to restore selected behaviours after those patches, not because Paper considers them normal supported mechanics.
A patch changes the server’s rules even when a client still displays a familiar contraption. A design that worked on an old vanilla server can stop producing duplicated items on Paper, and a player may interpret that as a broken machine. In reality, the server is enforcing its patched behaviour. Restoring the exploit is an explicit exception with a different support and risk profile.
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Paper’s support and stability warning
Paper’s documentation places these options outside its support contract. If enabling them causes lag, crashes or another server problem, Paper maintainers do not promise troubleshooting or a fix. The documentation also warns that unsupported settings may be removed at any time.
This is a stronger warning than “use at your own risk” for a redstone machine. It means an update can remove the escape hatch, change its semantics or leave a configuration entry unused. A world that depends on duplicated resources may then stop functioning after an upgrade, while the operator has no supported path to restore the old behaviour on Paper.
Paper maintainers point administrators who want all vanilla bugs back toward alternative server platforms such as Fabric or Sponge. That suggestion is a platform decision, not a guarantee that every exploit will behave identically. It also does not remove the need to assess performance, permissions, moderation and backup consequences on the chosen platform.
Why public servers should leave these options off
Economy and progression
Duplication changes supply without the mining, farming or trading effort that a server’s economy may assume. TNT can make large-scale excavation cheap; rails and carpet can be produced without their normal inputs; sand duplication can remove a resource bottleneck. Even if only a few players know the machine, the resulting items can enter shops, auction systems or automated farms and distort prices for everyone.
World integrity
Bedrock and End portal-frame exploits affect blocks that map designers use as boundaries. Breaking them can expose void areas, bypass containment, alter travel routes or compromise structures that were intended to be permanent. A headless-piston contraption may turn a protected-looking wall into a removable one.
Load and failure modes
Duplicated entities, falling blocks, redstone updates and explosions can increase tick work. The exact threshold depends on the build, hardware, world and contraption, so no universal “safe number” can be supplied. Paper’s warning covers the outcomes that matter operationally: lag, crashes and other failures are outside support.
Fairness and moderation
On a shared server, turning on an exploit is an administrative rule change, not merely a technical preference. Players who did not consent may lose builds or investments, and staff must decide whether duplicated materials are legal, confiscate them, roll back damage or reset markets. Those policies are difficult to enforce once the server itself permits the source of the items.
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A safe evaluation process for administrators
If you need to determine whether a legacy world or redstone design depends on one of these behaviours, evaluate it without exposing the production server.
- Identify the exact Paper build. Record the Minecraft version, Paper build number and the date of the test. Configuration support is build-specific, and the 1.19 file split means a path copied from an older guide may be wrong.
- Read the matching documentation first. Confirm that the key exists, which file contains it, what values it accepts and what default the build generates. Do not rely on a search snippet or an old forum answer for a current default.
- Clone the world into an isolated test server. Use a separate directory, separate ports and no player accounts or plugins that can connect to production. A backup is necessary because block-breaking and duplication tests can permanently alter terrain.
- Inspect rather than guess. Search the active configuration for the full key name. Check that the server is reading the file you edited; a correctly formatted change in an unused legacy file has no effect.
- Define a stop condition. Decide in advance what amount of lag, entity growth, corruption risk or unexpected block damage ends the test. Do not migrate a contraption to production merely because it works once in a small world.
- Record dependencies. Note which exploit a machine requires, which resources it duplicates and whether the design also depends on headless pistons, portal behaviour or permanent-block breaking. This prevents an apparently simple TNT design from importing several unsupported mechanics.
- Revert the test instance after measurement. Keep production configuration and worlds separate. If the experiment demonstrates that a design requires an unsupported exploit, redesign it with supported mechanics or choose a platform whose stated goals include that compatibility.
This process deliberately avoids treating the flags as a production recipe. It gives an administrator evidence about compatibility while limiting the blast radius of a crash, runaway machine or damaged world.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Diagnosing “TNT duping does not work”
The server is on a patched release
Paper 1.15.2 and later patched the relevant vanilla behaviour. A contraption copied from an older server may therefore fail exactly as designed on a current build. Verify the build before changing configuration.
The key is in the wrong file
After the 1.19 configuration split, global options belong in the configuration layout used by that Paper release. Searching only for paper.yml can lead to editing a file the server no longer reads. Conversely, an older installation may not have the newer file structure.
The key name is misspelled or no longer exists
Paper configuration keys are specific strings. Search for allow-piston-duplication rather than relying on a copied line number. If the key is absent, do not invent it or assume that a similarly named option controls the same exploit; the setting may have been removed or renamed in that build.
The machine uses more than TNT duplication
A design can require carpet or rail duplication, gravity-block duplication, headless pistons or permanent-block breaking in addition to TNT. The piston flag’s shared underlying bug explains why a TNT-only expectation can be misleading. Map the machine’s actual dependencies instead of enabling unrelated exceptions.
A forum claim mentions another setting
The effect of fix-entity-position-desync on TNT behaviour was not confirmed. Treat claims that it controls duplication as unverified until the current Paper documentation or source for the exact build establishes a relationship.
The server becomes unstable after a change
Stop the test, restore the previous configuration and use the backup rather than continuing to tune an unsupported exploit on production. Paper’s support warning means lag, crashes and similar failures are not covered as ordinary Paper bugs when these settings are involved.
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What to check before upgrading
- Search the release-specific Paper configuration for every unsupported key your world depends on.
- Confirm whether the key still exists and whether its default or accepted values changed.
- Test a copy of the world before replacing the production server.
- Inspect farms, portals, permanent-block boundaries and redstone machines that rely on patched behaviour.
- Keep a rollback plan that does not depend on the unsupported option remaining available.
No 2026 release-note change for these flags was established in the available material. That absence is not proof that nothing changed; it is a reason to check the current Paper documentation and changelog for the build you actually run.
Choosing a platform when vanilla exploit compatibility is a requirement
If a project’s design goal is to preserve every relevant vanilla bug, Paper may be the wrong platform. Its maintainers explicitly identify Fabric and Sponge as alternatives to investigate when all vanilla bugs are wanted back. Evaluate those platforms against the complete project brief—plugin or mod compatibility, administration tools, performance, update cadence, permissions and backup strategy—rather than switching solely for one TNT machine.
Another option is to keep the production server on supported settings and provide a separate technical-testing world on a platform that matches the experiment. That separation lets players use a predictable economy while engineers test legacy contraptions without exposing public builds or inventories to unsupported behaviour.
Administrator policy checklist
- Document whether unsupported settings are prohibited, allowed only in a named test world or part of a published server rule.
- Tell players whether duplicated items are legal and how staff will handle items created before a policy change.
- Protect backups from the same account or process that runs the server, so an exploit or crash cannot destroy every copy.
- Monitor tick health, entity counts and disk growth during any isolated experiment.
- Review the policy after every Paper upgrade because unsupported options can change or disappear.
Bottom line for the four flags
allow-piston-duplication is the setting associated with TNT, carpet and rail duplication; allow-unsafe-end-portal-teleportation covers gravity-block duplication through End portals; allow-permanent-block-break-exploits restores bedrock and End portal-frame breaking; and allow-headless-pistons permits a piston technique commonly used against permanent blocks. They live under unsupported-settings, their exact defaults are build-dependent except that headless pistons is documented as false, and Paper offers no support guarantee when they are involved.
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