DownloadSpASM ModGet the files on 9Minecraft
Guides
Step-by-step, in-game.
Debug Class Transformation IssuesIdentifying Transformation Problems When your custom class transformer isn't working as expected, systematic…Inject Code Into Multiple Game ClassesCode Injection via Class Transformation SpASM enables injecting custom code into game classes during loading. This…Register a Custom Class TransformerSetting Up Your Transformer SpASM Mod allows you to create custom class transformers that automatically scan and…Scan Multiple Classes Without Specifying NamesLeveraging SpASM's Automatic Scanning SpASM's core strength is scanning all loaded game classes without requiring you…
Frequently asked questions
How do I register a class transformer in SpASM?
Create a class that implements the ClassTransformer interface, then register it using the spasm:transformer entrypoint in your mod's metadata file. SpASM will automatically call your transformer on all classes during the loading phase.
Do I need to know exact class names to use SpASM?
No—that's the main advantage of SpASM. Your transformer receives every class being loaded, so you can scan and match classes by their methods, fields, or bytecode patterns instead of hardcoding names.
What's the difference between SpASM and Mixin?
SpASM gives you raw bytecode access to scan all classes without specifying targets upfront, while Mixin requires you to declare target classes and methods explicitly. SpASM is better for broad code analysis; Mixin is better for precise, targeted patches.
Can multiple mods use SpASM at the same time?
Yes. Each mod registers its own transformers via the spasm:transformer entrypoint, and SpASM applies all of them during class loading. Order of execution depends on mod load order.
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