AntiFly

Flight restriction that does one job properly. Lightweight Bukkit + Fabric plugin/mod by CevAPI.

Current release: 1.1.6

AntiFly is not a full anti-cheat, and that is deliberate. It is built for servers that want to restrict flight and nothing else - no reach checks, no killaura heuristics, no combat module quietly flagging your players at 3am. What you get instead is flight control accurate enough to leave legitimate movement alone.

Why AntiFly

• It never trusts the client. Ground and support are verified server-side. A client claiming onGround cannot talk its way past a check.
• Layered detection, not one threshold. Buffered air, hover and anti-kick suspicion sit alongside a sustained-air backstop, so slow level flight and gentle bobbing are caught - not just obvious speed hacks.
• Setbacks nobody complains about. Players are corrected to their last known valid support instead of being yanked out of the sky mid-air.
• Elytra handled properly. A trajectory verifier predicts the next vanilla glide step from pitch, yaw and prior velocity, then weighs residual motion, excess energy, unnaturally constant speed and impossible turns - and only acts when several channels agree. Rocket boosts, steep dives, pull-ups and obstacle crashes are all left alone.
• Teleport-aware. /tp, ender pearls, chorus fruit and portals are rebased rather than mistaken for flight, so legitimate travel never rubber-bands.
• It does not advertise itself. The root command is permission-gated on both platforms so clients that probe a server's command list with suggestion packets get nothing back.
• One shared codebase. The same checks run on Paper and Fabric, so a detection is never fixed on one platform and forgotten on the other.

Hunger Mode

Hard blocks are not always what a survival server wants. /antifly hungermode on replaces them with a penalty that fits the game:

• Food drains first, scaling with speed and never falling below a minimum while airborne - so an idle hoverer still pays.
• Then health, once the flight has lasted long enough (or the player is already starving). Damage ticks slowly, so a landing attempt is always survivable.
• Vanilla gliding and rockets stay free unless the movement shows genuine exploit evidence.

The upshot: no rubber-banding, no teleport-loop complaints, and an economy that discourages flight naturally instead of a wall that just frustrates players.

Void (Nether Roof/Below Bedrock) Access

A bonus toggle for servers that want to close off the void as well. /antifly voidaccess off covers the Nether roof (Y ≥ 128), the void below the Nether and the void below the Overworld.

• With Hunger Mode off, players who enter are returned to their last safe position, including while mounted.
• With Hunger Mode on, entry is allowed but costs health directly - one hit on entry, then once per second while they stay. The usual hunger phase is skipped here, and exempt players are spared.

Platforms

• Bukkit family: 1.21.x - 26.3 (Bukkit, Spigot, Paper, Purpur, Folia)
• Fabric: 1.21.11 / 26.1.2 / 26.2 / 26.3

Server compatibility

The Paper build is compiled once against the oldest supported API (1.21.1) so a single jar runs on every Bukkit-family server from 1.21.x up to 26.3. Every build re-verifies that the sources still link against the oldest Paper API, the newest Paper API, and plain Spigot/Bukkit:

./gradlew :paper:checkPaperApiCompatibility

Anything that only exists on some servers is probed at runtime and falls back to plain Bukkit:

• region schedulers (Paper/Purpur/Folia) with a Bukkit scheduler fallback
• Folia entity scheduling so Hunger Mode health changes run on the thread that owns the player
• Entity#isInLava() with a block probe fallback
• the Adventure action bar (Paper family); servers without it simply show no debug action bar

Install

• Bukkit family: drop the jar into plugins/
• Fabric: drop the jar into mods/

Commands

The same set on Paper and Fabric. Requires op or antifly.admin on Paper, moderator-level permissions on Fabric.

• /antifly enable|disable|status|help
• /antifly hungermode <on|off> - swap hard blocks for the hunger and health penalty
• /antifly voidaccess <on|off> - allow or block the void (default on)
• /antifly alerts <off|game|console|both> - where violation alerts are delivered
• /antifly reload - re-read the config from disk, no restart needed
• /antifly set - list every tunable key with its current value

Also available: /antifly set <key> [value], /antifly debug, /antifly exempt / unexempt, /antifly reset and /antifly disabledworlds. The full command reference is in CONFIGURATION.md.

Configuration

Every check is tunable at runtime with /antifly set <key> <value>. Changes apply instantly and auto-save, so there is no restart and no file editing.

Defaults are chosen to stay forgiving of vanilla movement - sprinting, Depth Strider, Dolphin's Grace, Speed potions, wind charges, knockback and rockets are all expected and unpunished - so the common case really is "install it and leave it alone".

• Paper / Bukkit: plugins/AntiFly/config.yml
• Fabric: config/antifly.json

CONFIGURATION.md documents every key and its default, the full command reference, the Elytra trajectory verifier in depth, Hunger Mode and void tuning, and which keys are platform-specific.

Permissions (Paper)

• antifly.admin (default: op) · antifly.alerts (default: op)

License

GNU General Public License v3.0 or later (GPL-3.0-or-later)