Naming drift

Verified against Minecraft 26.2 · Reference · The translation layer: every name a 1.21-era reader will reach for that 26.2 does not have, and what it is called now.

Rule three of this corpus is newest version only: no page says “in 1.21 this was…”, because version-difference prose is the first thing to rot and the last thing anyone rereads. That rule costs something, and this page is where the cost is paid back once. Every page assumes you are reading the 26.2 tree; this page assumes you are not, yet, and are still typing the names you learned somewhere else.

Two audiences. A reader coming from 1.21 — the version most public writing, most tutorials and most model weights are anchored to — needs the first table: the old name on the left, what to grep for on the right. A reader coming from Yarn (Fabric’s community mappings) needs the last one: not a version difference at all, just a different name for the same class in the same version.

The one sentence: if a name in your head does not appear in the tree, it is probably on this page.

How to read the tables

The left column is italic, not backticked. Most of these names do not exist in 26.2, and tools/verify_names.py — which checks every backticked identifier on every page against the decompile — would reject the page if they were. Italics is the corpus’s mark for a name, but not a 26.2 name. The right column is backticked and therefore verified: those names are in the tree.

“gone” in the right column means exactly that: there is no replacement class, the responsibility moved into something structurally different, and the entry names where it went. Those are the interesting rows — a rename is a nuisance, a disappearance is a design change, and the page named beside each part explains it.

Every row here was found the same way: a fact-sheet agent reading the 26.2 decompile went looking for a name it expected and did not find it. The table is therefore not exhaustive — it is exhaustive over the names the corpus needed. Two hundred and forty-three rows, and the distribution is itself a finding: the three biggest tables are commands (36), the server (31) and items (30), and the fourth is rendering (27). The client was rewritten around extract-then-render, which is why almost nothing at the top of the render stack kept its name — but the permission rewrite and the game-rule registry moved more names than the renderer did.

The four you will hit in the first ten minutes

Identifier is ResourceLocation. Lightmap is LightTexture. DeltaTracker is Timer, and partialTick is now a DeltaTracker.Timer you ask rather than a float you are handed. And Gui no longer means the HUD: the HUD is Hud, held as Gui.hud, while Gui is the screen and overlay manager that also owns Gui.screen and Gui.setScreen — so a 1.21-era Minecraft.setScreen call site is now on Gui. Both Gui and Hud exist, which is the single most confusing pair of names in the tree.

The tables

Everywhere

Part II — Foundations

Part III — The server

Part IV — The world

Part V — Blocks

Part VI — Entities

Part VII — Items and inventories

Part VIII — The player

Part IX — Networking

Part X — The client

Part XI — Rendering

Twenty-seven rows, and almost all of them are one refactor: extract then render.

Part XII — World generation

Part XIII — Commands and data packs

The permission rewrite is the largest single break in this table: the integer permission level is gone from the whole command API, replaced by PermissionSet and PermissionCheck in net/minecraft/server/permissions. The ints survive only in ops.json, in server.properties and on the wire.

The shape changes, not just the names

A rename table flatters the reader: it suggests that if you learn the two hundred and forty-three rows above you can read the tree. You cannot, because a dozen of these rows are one design change each, and the change is what the corresponding page is about. The recurring ones:

• Tags on an item became components. ItemStack.getTag / getOrCreateTag have no replacement; a stack is an Item plus a PatchedDataComponentMap and every former tag key is a DataComponentType in DataComponents — data components, items and stacks.
• Hand-written serialisation became codecs. Packet.write is gone: a packet is a record with a StreamCodec the protocol table reads. ItemStack.save is gone: there is ItemStack.CODEC and, for saved data, the ValueOutput façade — packets and stream codecs, codecs, NBT and JSON.
• Rendering split into extract and render. GuiGraphics, EntityRenderer.render, LevelRenderer.renderLevel, MultiBufferSource and every RenderSystem state setter are gone or repurposed, because the frame now builds an immutable render state on the game thread and draws from it — the frame, Blaze3D, entity rendering.
• Per-dimension and per-biome constants became one attribute system. DimensionSpecialEffects and most of BiomeSpecialEffects are gone; fog, sky, water colour, ambient sound and music are EnvironmentAttributes resolved through an EnvironmentAttributeProbe over a stack of layers — lightmap, fog and sky, biomes.
• Enums of behaviour became registries of data. EnchantmentCategory, MobSpawnType, BlockPathTypes, GenerationStep.Carving and Biome.BiomeCategory are all gone, replaced by item sets, registry records, HolderSets or nothing at all.
• UUIDs became identifiers. An AttributeModifier is keyed by Identifier, not a UUID, which is why a data pack can now name one — attributes.
• Sides split. Entity.hurt became Entity.hurtServer and Entity.hurtClient; Player.attack is still there but the packet that reaches it is ServerboundAttackPacket, a record of one integer, and ServerboundInteractPacket is right-click only. The general rule: where 1.21 had one method that checked Level.isClientSide, 26.2 tends to have two methods — damage and death, the sword swing.

Yarn

Yarn is Fabric’s community mapping set. It is not a different version of the game and nothing on this list is a change: it is the same 26.2 class under the name a Fabric modder has in their head. Only the ones that actually trip people are listed — where the Yarn and Mojang names differ enough that grep fails.

Both columns are italic here, because Yarn names are not in the decompile and verify_names.py cannot check them; the Mojang column is the one this corpus uses everywhere else, and every one of those names is backticked and verified on its own page.

The last row is the joke that keeps giving: the single most-cited example of “Yarn names are better” stopped being an example, and a decade of Fabric code now compiles against a Mojang-named class with the Yarn name.

What a rename table cannot tell you

• A verified name is not a correct claim. verify_names.py proves the right-hand column exists; it cannot prove the left-hand column ever did. The 1.21 side of this table is the only unverifiable content in the corpus, which is why it is confined to one page.
• The names did not move where you would guess. Rendering is the fourth-largest table, behind commands, the server and items. Two rewrites nobody advertised — permissions ceasing to be integers, and game rules becoming a registry — renamed more identifiers than the render-stack refactor did, and the render one is the famous half only because its classes are the ones tutorials name.
• Renames cluster with rewrites. No part of the tree renamed a class and kept its design; where the name changed, the responsibility usually moved too. Reading the row is not enough, which is what the linked page is for.
• Two subsystems have no rows at all, and that is the answer. Dialogs (net/minecraft/server/dialog and its client screens) and the JSON-RPC management server postdate 1.21 entirely: there is no old name to look up, and a reader who cannot find one is not missing a row. Game tests are the opposite case — the whole 1.21 API is gone, which is why they have five.
• Minecraft.setScreen is a trap rather than a rename. Minecraft.setScreenAndShow exists in 26.2 and a 1.21-era reader grepping for the old name will land on it, then wonder why the screen stack behaves differently. The method that replaced the old one is Gui.setScreen.
• Some names survived and changed meaning, which is worse than a rename because grep still finds them: Gui (now the screen manager, not the HUD), Material (now a texture reference in client/resources/model/sprite, not a block property), ParticleGroup (now a per-render-type bucket, not a count limit), Strategy (now top-level, not nested in PalettedContainer), and MultiVariant, whose name survives only in the data-generator package while the runtime type is gone.

Where to look

Identifier, then Holder and HolderSet (net/minecraft/core), then DataComponents — those three carry more of the drift than any others. After that, pick the part you are lost in and read its page rather than its rows.

Rules: names, never code · how the system works, not how the code reads · newest version only · every backticked name passes tools/verify_names.py.