Afterburner

Afterburner makes Minecraft run faster without changing how the game looks or plays. It works on a client, on a server, or both. The mod is customizable, and you can check out video settings for configuration. (or config/afterburner.properties)

What it improves

Rendering

• Batched chunk drawing: each 128x64x128 block region is drawn with one call instead of one call per chunk section.
• Smaller chunk vertices: 16 bytes per vertex instead of 28, so the graphics card reads less for every block face. Chunks also take less graphics memory.
• Occlusion culling: chunks hidden behind nearer terrain (hills, caves, walls) aren't drawn. Works on OpenGL and Vulkan.
• Entity culling: mobs, chests, signs and other entities hidden behind terrain aren't drawn.
• Face culling: block faces that point away from the camera are skipped.
• Translucent face culling: the same for water, glass and ice.
• Leaf culling: faces deep inside a tree's leaves, which the leaves in front hide, are skipped.
• Faster draw prep: skips the per-frame work for chunk layers that have nothing to draw.
• Off-screen chunk building: chunks around you get built while the builders have time, not only once you look at them, so turning around shows fewer holes.
• Cheaper texture filtering: smooth filtering reads each texture 4 times per pixel instead of 8 or 9. The picture stays the same.

Memory

• Smaller chunk buffers: GPU memory for chunks grows as needed instead of being reserved 128 MB at a time. On laptops with built-in graphics, that memory is your normal RAM.
• Freed build copies: chunks let go of the copy of the blocks they were built from. Vanilla keeps one per chunk.
• Memory trim: while the game is paused or in the background, Java gives unused memory back to the system.
• Leaner chunk sections, shared block shapes, leaner block states: less memory for every block and biome container.

World and server

• Parallel world generation: trees, ores and structures are placed on every CPU core instead of one. If a generation step ever fails, Afterburner goes back to one thread for the rest of that run.
• Faster lighting: light updates remember the sections they're working in instead of looking them up for every block. It uses the same algorithm as vanilla, so the result is the same.
• Faster collisions, entity searches, mob AI, explosions, redstone dust and spawning: less work per block, per search and per mob.
• Sleeping idle furnaces and campfires, and scheduled ticks parked where nothing is happening.

Forge and NeoForge only (server side)

• Hoppers: a hopper that has nothing to do goes to sleep until something changes (and wakes now and then to double-check), and hoppers remember the container next to them. In our Forge 26.3 test, a server with 1,800 stuck hoppers took 18.5 ms a tick without Afterburner and 8.8 ms with it.
• Faster water and lava flow, pathfinding, entity tracking, item merging, and finding structures off the main thread.
• Cheaper network work: chunk packets are shared between the players who get them, packed once, and packed at a lighter zlib level.

Other

• Lower worker priority: background workers run just below normal priority, so frames come first when every core is busy.
• Accurate ping and Clicks at Once (26.3): a player's ping is measured when the reply arrives, not when the busy main thread gets to it; an attack or placed block is sent the moment it is pressed.

Slow connections (Minecraft 26.3)

For a player with very little bandwidth, on a Forge 26.3 server:

• /afterburner slow <player> (op) gives a listed player a smaller view distance and the strongest packing. A player whose connection stays backed up gets it on their own.
• /afterburner net (op) shows what the server sends each player, by kind of packet.
• Smaller chunks from Afterburner servers (Fabric 26.3 client, in the settings, off by default): chunks arrive packed with LZMA2, without their light (the game works it out), and as a 16-byte reference when you kept the chunk on your disk from last time. In our tests: about a third fewer bytes for chunks seen the first time, two thirds to four fifths fewer when you've seen them before. Other servers are not affected, and ViaProxy passes it through.

Settings by dimension (Forge 26.3 server, off by default)

config/afterburner-dimensions.properties sets things separately for the Overworld, the Nether, the End and any other dimension:

• Dropped items (dimensionItems switch): how long an item lasts, how close items must be to merge, and how many item entities one chunk may hold (past it the oldest go). The file starts the Nether and the End at half the item lifetime and a wider merge range, and leaves the Overworld as in vanilla. Item farms that leave items lying around may want longer lifetimes or no limit.
• Slower AI for far mobs (farMobAi switch): how far from a player mobs start thinking less often, per dimension.

Experimental (off by default)

A shader pack loader, FSR-style upscaling and far terrain (land past the render distance, drawn from chunks the game has seen) come with the mod (Minecraft 26.3, and 1.21.1 on Forge, NeoForge and Fabric). They do nothing until you choose them, far terrain starts off, and they turn themselves off with Sodium or Embeddium, Iris or Oculus, Voxy or Distant Horizons. Expect rough edges and tell us what you see.

Versions

The list of optimizations differs between versions: Minecraft 26.3 has the most. See the files' notes, or Features.java in the source.

Minecraft	Fabric	Forge	NeoForge
26.3	yes	yes	yes (beta)
26.2, 26.1.2		yes (beta)
1.21.11	yes (beta, partial)	yes
1.21.10, 1.21.8, 1.21.5, 1.21.4, 1.21.3		yes (beta)
1.21.1	yes	yes	yes

Fabric needs Fabric API. The Minecraft 26.x builds need Java 25; the 1.21.x builds Java 21. Fabric 1.21.11 is a first build: it has the server side and some of the client side, and no chunk batching or occlusion culling yet.

Benchmarks

Afterburner 0.2.2 off and on, in turns, measured on one laptop (i7-1255U, integrated Intel UHD graphics). A dedicated graphics card hasn't been tested, so these frame rates may not carry over.

Forge 26.3 server, 4 runs each way, median ms per tick (lower is better):

Scene	Off	On
World alone, 2,304 loaded chunks	14.3	10.9
400 cows	18.0	12.2
1,800 idle hoppers	11.3	8.9
1,800 stuck hoppers	18.5	8.8

Each scene ran on its own after a warm-up, on the CPU's 8 efficiency cores, so a run doesn't depend on which core it lands on.

Fabric 26.3 client, render distance 16, flying over terrain, 3 runs each way, median:

	Off	On
Average FPS	108.6	213.4
1% low FPS	59.3	96.3

Compatible with

Afterburner is built to leave a part to the mod that does the same job: Sodium and Embeddium (rendering), Lithium and Radium (game logic), FerriteCore and ModernFix (memory), Starlight, C2ME (chunk system), Iris and Oculus (shaders). The overlapping part is simply off while the other mod is there.

Tested with

Afterburner 0.2.2 next to each mod on its own, and in a set of them where the table says so: a dedicated server started, made a world and stopped cleanly, and a client opened a world. These are short runs, not long play, so tell us if a combination misbehaves.

Minecraft	Loader	Tested with	All together	Notes
26.3	Fabric	C2ME, Distant Horizons, Entity Culling, FerriteCore, ImmediatelyFast, Iris, Lithium, Sodium	yes
1.21.11	Fabric	C2ME, Distant Horizons, Entity Culling, FerriteCore, ImmediatelyFast, Iris, Lithium, Sodium	yes
1.21.1	Fabric	C2ME, FerriteCore, Iris, Lithium, Sodium		Iris checked on a normal client launch, not in the dev setup.
1.21.1	Forge	Entity Culling, ImmediatelyFast		Most of these mods have no Forge 1.21.1 build. The test client crashed in a Forge loot error (LootModifierManager) when a block dropped items, and plain Forge did the same with no Afterburner installed.
1.21.1	NeoForge	C2ME, Create, Distant Horizons, Embeddium, FerriteCore, Iris, Lithium, ModernFix, Sodium	yes	Sodium and Iris are client mods: their own check stops a dedicated server with or without Afterburner. Fine on the client.

Note:

Credits and licenses: MIT. Sodium, Lithium, FerriteCore and Iris are credited for the designs this follows (no code of theirs is used); AMD's FidelityFX Super Resolution 1 (MIT) for the upscaling. The full notices are in THIRD_PARTY_NOTICES.md inside every jar.