Compatibility and Status

Compatibility and status

Per-mod results are on the compatibility site. Back to Home.

Legacy version	Status
1.7.10	Beta. Iron Chest, Twilight Forest, Thaumcraft, HBM, RFTools, Thermal Expansion and others work in game; Galacticraft with its addons runs with per-planet gravity. In-game self tests (every block placed and used, every item used, every mob spawned) of the GT New Horizons pack and a 130-jar 1.7.10 list rate 166 mods as working and 57 as partly working; 20 fail during loading (see the compatibility list). Mod biomes, world types and dimensions generate; mod entities spawn, tick, fight and save; entity rendering (including the player renderer), armour and held items, dimension fog/sky and Twilight Forest's portal are bridged, though not verified in game for every mod. All synthesized API classes pass JVM verification.
1.12.2	Alpha (issue #64). Content mods load and play in a real client: blocks, items, mobs with their own renderers and AI, GUIs, world generation, loot, natural spawning, advancements and Forge events. Implemented: the FML lifecycle, registry events (blocks, items, potions, enchantments, sounds, biomes, entities, recipes, villager professions, custom registries made with RegistryBuilder), items with subtypes, blocks and block states (one meta property mapped through getStateFromMeta/getMetaFromState), tile entities with client sync, capabilities (items, fluids, energy), networking channels, recipes (code recipes become data pack recipes), ore dictionary, tools/armor, fluid data model, @ObjectHolder, @SidedProxy, @EventBusSubscriber, coremod plugins and vanilla constants (Blocks, Items, ...), the server lifecycle events (FMLServerStartingEvent and the others) and server commands (ICommand/CommandBase commands become modern commands), and the registries mods add to at load time (criteria triggers, loot functions and conditions, data serializers, villager trades, Forge's biome lists, grass seeds, enderman-carriable blocks). Mod blockstates, item models (ModelLoader) and model/texture names renamed after 1.12 are translated,. The client has run with Botania, Blood Magic, Mekanism, EnderIO, Immersive Engineering, Tinkers' Construct, Quark, Biomes O' Plenty, Vampirism, the Aether and Scape and Run: Parasites; some models still show as missing. Server tests: of 32 big jars (EnderIO, Mekanism, Thermal, BuildCraft, AE2, Botania, Blood Magic, Tinkers, Forestry, Thaumcraft, Twilight Forest, BoP, ...) 1 of 50 mod ids still fails (BuildCraft Silicon) and about 2060 blocks, 3480 items and 3670 recipes register (@Config classes are filled from their config files; vanilla items with metadata map to their flattened modern items); of 39 more jars (Roots, Vampirism, Totemic, RFTools, Pam's HarvestCraft, The Betweenlands, Ice and Fire, TechReborn, ...) 16 of 42 mod ids fail, some from missing dependency jars. In the larger 116-jar server test (2026-10-30) about 5,050 blocks and 10,170 items register, 11 mods fail (10 of them because a dependency jar is missing), and the self test places and right-clicks every block and uses every item without errors; per-mod ratings are on the compatibility site. Every legacy API the 1.12.2 test mods use has an implementation, except internals with no 1.21.1 counterpart. Blockstates in Forge's v1 format (defaults, per-variant textures), code-defined state mappers, OBJ models and Forge's model loaders are translated. Also implemented: entities with their AI, renderers and models (vanilla mob classes included), containers and GUIs, Forge fluids that flow, world generation (IWorldGenerator, biome layers, terrain events, structures), loot tables, natural spawning, advancements, the scoreboard and the Forge client events. Still missing: rail physics for mod minecarts and riding mod horses, and some vanilla renderers (boats, horses). Results per mod are on the compatibility site. Performance, bug-fix and mixin-loader mods (FoamFix, BetterFPS, VanillaFix, ...) are skipped.
1.6.4	Started (2026-11-06): loader groundwork and corpus; no 1.6.4 mod runs yet (next after 1.12.2).
1.5.2	In development (right after 1.6.4).
1.4.7	Started (2026-11-06): loader groundwork and corpus (65 mods); no 1.4.7 mod runs yet (after 1.5.2).
1.20.1	Started (experimental, off by default; experimental.forge1201). Forge 1.20.1 mods are remapped in place onto NeoForge 1.21.1 (SRG to Mojang names, Forge to NeoForge). So far: jar detection, the renames, mods.toml conversion and the first compatibility layer; no 1.20.1 mod has been run in game yet (see the estimate).
1.19.2, 1.18.2	Planned (after 1.20.1).
1.16.5	Planned (after 1.18.2).
1.2.5	Planned (after 1.16.5).
1.3.2	Only on demand.

Not supported (and likely never fully): coremod transformers and mixins that patch legacy Minecraft code itself, LaunchWrapper tweakers. They are reported, and the rest of the mod still loads. Where a coremod only exists to change engine behaviour that has a modern equivalent, the layer bridges the behaviour instead (Galacticraft's gravity and silent space are applied per dimension, see Dimension physics in Bridges).

Known compatibility issues

Found by loading a ~140-mod 1.7.10 test pack (test-mods/) together. Everything not listed here loaded in the last full run; "loads" does not mean every feature was played through.

Mod / combination	Issue	What to do
RotaryCraft (with DragonAPI) and Forestry 4.2.16	DragonAPI's wood list asks Forestry for blocks named planks2 and slabs1-slabs4, which Forestry 4.2.16 does not register (it has planks and slabs); the list then holds a null block and RotaryCraft is disabled at post-init. The same names broke Binnie's pre14. DragonAPI and ReactorCraft load.	Use a Forestry/DragonAPI pair built for each other (no matching 1.7.10 Forestry build was found on Modrinth).
Binnie's Mods 2.0-pre14 with Forestry 4.2.16	Binnie was built for an older Forestry API (getProducts, getLogStacks, planks2 do not exist in 4.2.16); ExtraBees, Botany, BinnieCore and ExtraTrees fail, and anything that runs their recipes (ThermalExpansion) with them.	Use Binnie's Mods 2.0.22.7 (loads); Binnie Patcher is then not needed.
Witchery + the Reika mods	Witchery's potions default to ids 32-75; RotaryCraft's freeze potion is 35, ChromatiCraft's potions 36-42 and ReactorCraft's radiation 140, so DragonAPI refuses to start.	Move Witchery's potions: in config/witchery.cfg add 32 to every id in the potions block and to PotionStartID (64-107; keep ids below 128, 1.7.10 stores potion ids as a byte). Legacy Connector saves effects by name, so worlds keep their effects.
ProjectRed Expansion + Runic Dungeons	Both use enchantment id 80. 1.7.10 crashed; here one enchantment is moved to a free id and a warning is logged.	Change an id in the mods' configs to keep ids stable.
Mystcraft + NetherOres	NetherOres swaps the vanilla quartz ore block through CoFH registry reflection. Works, because replaced vanilla blocks keep the vanilla identity.	None.
Mods that patch Minecraft's own classes with coremods	The patches cannot run on the shim classes. Only DragonAPI's crafting-list and smelting hooks (CoremodHooks) and Fisk's Heroes' hooks (compat.fiskheroes: movement, model poses, Moon/Quantum Realm and gravity-power gravity, healing factor heal rate, stealth against mobs, speedster slow motion as the server tick rate, suit footsteps, size/scale of players, camera roll and shake, first-person suit arms, left-click locks) are provided; other such patches do nothing. Not wired for Fisk's Heroes: the off-hand item in first person, night-vision overrides, intangible light tweaks, inventory preview scale; on a dedicated server heroes fly only with allow-flight=true (as in 1.7.10).	Report the mod.
The Betweenlands (1.7.10 1.0.6 and 1.12.2 3.9.6)	Both load and their dimension generates and renders. Its own mob spawner (MobSpawnHandler) produces no mobs yet, and some item models and sounds are missing (the sound ambience handler fails on a missing sound accessor). The 1.7.10 version replaces the title screen with its own; the shim's GuiMainMenu provides vanilla's buttons for it.	Use spawn eggs for now.
Morph 0.9.3 (1.7.10) with iChunUtil	Morphing into mobs and the morphed size work. The kill and morph-down animations and the morphed model's placement are still being fixed (#153).	None yet.
Thermal Expansion / Thermal Dynamics (1.7.10)	Machines and block items in the inventory show their base model (the per-machine item renderer is not reproduced); ducts do not draw their connections yet.	None yet.
Railcraft and EnderIO anvils	ContainerRepair is implemented with the vanilla field names and rules; not yet checked in game.	Test in game.
HBM's pylons/substations, RFTools screens, Thermal Expansion tanks and caches, Runic Dungeons portal	Fail in the automated block self test, which uses a fake player and no tile state; not confirmed in real play.	Test in game.
Decocraft	Loads through a stand-in for the JDK-internal PNG reader; models not checked in game.	Test in game.
Tinkers' Construct and other mods whose getSubItems reads client-only icon arrays	Subtype discovery registers icons against a detached register; blocks whose arrays still stay empty get metadata 0 only until used.	None.
Villager professions, trades and village components (VillagerRegistry)	Modded professions with skins and trade handlers appear on some new unemployed villagers (they have no job site unless villagers.jobSites maps one). Village creation handlers (Witchery's shops, walls, towers; AgriCraft's greenhouses) build their components inside modern villages, planned beside the modern streets and facing them (1.7.10's getNextComponentNN/PP); layouts that continue from a mod's own paths get the next building as 1.7.10 chose it, and plans are kept per village so every chunk builds the same components. The vanilla piece factories mods call (House1.func_74898_a ...) build the modern village building of the same use, turned to the path. Modded villagers have no job site unless villagers.jobSites maps their profession to a block (1.7.10 professions declare none; see Configuration).	Fixed for components; job sites only by config.
/locate structure	Vanilla structures are found in legacy biomes (they join the vanilla biome tags). Structures drawn by legacy generators are found with /locate structure <mod>:legacy/<name> (the generator's name, lower case; listed by tab completion), at any distance, from an index of the builds recorded as chunks generate. Terrain that has not generated yet cannot be searched: legacy generators decide while building and keep state that a dry run would corrupt (see World generation).	Partly fixed.
JourneyMap / Custom Main Menu / Inventory Tweaks (1.7.10 versions)	Loaded like any other legacy mod. Custom Main Menu replaces the title screen (GuiOpenEvent/GuiScreenEvent are bridged; its panorama, logo and splash draw, buttons are being verified). The other two are not verified.	Report what you see.
FastCraft, Hodgepodge, NEID and other engine/launcher patches	Intentionally not loaded (see Bridges).	Use their modern equivalents.

What happens to a mod

After launching, read logs/legacyconnector-report.txt. For every legacy jar it lists the detected version and mod ids, references that could not be linked, and which legacy APIs were synthesized (they link but do nothing yet). At runtime, LegacyConnector/Stubs log lines show which synthesized APIs are actually called.

What the compatibility ratings mean

The compatibility site rates every mod with one of these (renamed on 2026-11-06 to plain words; the data keys did not change, so old links and reports still work):

Rating (was)	Meaning
Fully playable (Near-perfect)	You can play it in survival; the maintainer played it and only small problems are known.
Mostly playable (Playable)	Played in survival and most of it works; some mechanics or abilities are broken or were not tried.
Basics work (Works)	Its blocks, items and mobs showed up and behaved in a test; deeper mechanics were not checked.
Partly working (Partial)	It loads and part of it is usable, but some features are known to be broken.
Starts, untested (Loads)	It starts without errors and passes the startup check; nobody has played it yet.
Does not start (Fails to load)	The game starts but the mod is disabled because it failed while loading.
Crashes the game (Crashes)	Using it takes the whole game down.
Not tested (Untested)	No result yet.