ArisuFxPy

A Unity asset extractor for Python based on AssetStudio.

Next to extraction, ArisuFxPy also supports editing Unity assets. Via the typetree structure all object types can be edited in their native forms.

# modification via dict:
    raw_dict = obj.parse_as_dict()
    # modify raw dict
    obj.patch(raw_dict)
# modification via parsed class
    instance = obj.parse_as_object()
    # modify instance
    obj.patch(instance)

🚀 Why ArisuFxPy? (Key Enhancements over UnityPy)

• 🛡️ UABE Avalonia-Grade Compatibility (Zero False Encryption Errors):
  Fixed a longstanding upstream UnityPy bug where normal Unity AssetBundles with engine version < 2020 or modern archives using 16-byte alignment (0x200) were falsely treated as encrypted ("The BundleFile is encrypted, but no key was provided!"). ArisuFxPy accurately distinguishes alignment padding from Unity CN DRM, opening and saving all standard bundles seamlessly without requiring fake keys.
• 📦 Trailing Padding & Robust Offset Handling (BlocksInfoAtTheEnd):
  Fixed critical LZ4 decompression errors (Decompression failed: corrupt input or insufficient space in destination buffer. Error code: 62) on AssetBundles containing trailing padding or appended container metadata. ArisuFxPy calculates exact block index offsets from the internal UnityFS header size, matching UABE Avalonia.
• 🔧 Manual Target Byte Padder (Hex Padding):
  Built-in utility in bundle_modder.py (Option 6) to automatically inject null bytes (0x00) to match exact target file sizes required for anti-cheat verification and strict game integrity checks.
• 📱 Android & Termux 1st-Class Support:
  Designed for mobile game modders and data-miners. Includes 1-line installation (install.sh), Termux-friendly pure Python fallbacks, and directory-shadowing fixes.
• 🎮 Interactive Modder Tool (bundle_modder.py):
  A built-in interactive CLI tool to inspect asset tables, export/import text and JSON dumps, modify raw asset data, re-pack bundles with LZ4/LZMA, and apply custom hex padding on PC and Android.

If you need advice, want to discuss game modding / data-mining, or need support, feel free to join our official Telegram Group (@hackinjectlab).

If you're using ArisuFxPy for a commercial project, a donation to a charitable cause or a sponsorship of this project is expected.

As ArisuFxPy is still in active development, breaking changes can happen. These changes are usually limited to minor versions (x.y) and not to patch versions (x.y.z). So in case that you don't want to actively maintain your project, make sure to make a note of the used ArisuFxPy version in your README or add a check in your code. e.g.

if ArisuFxPy.__version__ != '1.9.6':
    raise ImportError("Invalid ArisuFxPy version detected. Please use version 1.9.6")

1. Installation
2. Example
3. Important Classes
4. Important Object Types
5. Configurations
6. Credits

Installation

Python 3.8 or higher is required.

💻 PC & Termux Quick Install (via PyPI)

pip install ArisuFxPy

Or install bleeding-edge from GitHub:

pip install git+https://github.com/arisugpt/ArisuFxPy.git

Or install from source:

git clone https://github.com/arisugpt/ArisuFxPy.git
cd ArisuFxPy
python -m pip install .

---

📱 Android (Termux) Installation Guide

⚡ 1-Line Auto Installer (Recommended):

Open Termux on your phone and run this single command:

curl -sSL https://raw.githubusercontent.com/arisugpt/ArisuFxPy/main/install.sh | bash

This automatically installs Python, Clang, Git, builds dependencies, and installs ArisuFxPy.

🛠️ Manual Termux Installation:

If you prefer running commands manually:

# 1. Update Termux and install required tools
pkg update -y
pkg install python git clang make -y

# 2. Install ArisuFxPy and CLI table viewer
pip install git+https://github.com/arisugpt/ArisuFxPy.git
pip install tabulate

🎮 Interactive Unity Asset Modder & Dumper:

To run the interactive bundle modding tool on Android / PC:

curl -sSL https://raw.githubusercontent.com/arisugpt/ArisuFxPy/main/bundle_modder.py -o bundle_modder.py
python bundle_modder.py

Notes

Windows

Visual C++ Redistributable is required for the brotli dependency. In case a new(ish) Python version is used, it can happen that the C-dependencies of ArisuFxPy might not be precompiled for this version. In such cases the user either has to report this as issue or follow the steps of this issue to compile it oneself. Another option for the user is downgrading Python to the latest version supported by ArisuFxPy. For this see the Python version badge at the top of the README.

Crash without warning/error

The C-implementation of the typetree reader can directly crash Python. In case this happens, the usage of the C-typetree reader can be disabled. Read this section for more details.

Example

The following is a simple example.

import os
import ArisuFxPy

def unpack_all_assets(source_folder: str, destination_folder: str):
    # iterate over all files in source folder
    for root, dirs, files in os.walk(source_folder):
        for file_name in files:
            # generate file_path
            file_path = os.path.join(root, file_name)
            # load that file via ArisuFxPy.load
            env = ArisuFxPy.load(file_path)

            # iterate over internal objects
            for obj in env.objects:
                # process specific object types
                if obj.type.name in ["Texture2D", "Sprite"]:
                    # parse the object data
                    data = obj.parse_as_object()

                    # create destination path
                    dest = os.path.join(destination_folder, data.m_Name)

                    # make sure that the extension is correct
                    # you probably only want to do so with images/textures
                    dest, ext = os.path.splitext(dest)
                    dest = dest + ".png"

                    img = data.image
                    img.save(dest)

            # alternative way which keeps the original path
            for path,obj in env.container.items():
                if obj.type.name in ["Texture2D", "Sprite"]:
                    data = obj.parse_as_object()
                    # create dest based on original path
                    dest = os.path.join(destination_folder, *path.split("/"))
                    # make sure that the dir of that path exists
                    os.makedirs(os.path.dirname(dest), exist_ok = True)
                    # correct extension
                    dest, ext = os.path.splitext(dest)
                    dest = dest + ".png"
                    data.image.save(dest)

You probably have to read Important Classes and Important Object Types to understand how it works.

Users with slightly advanced Python skills should look at ArisuFxPy/tools/extractor.py for a more advanced example. It can also be used as a general template or as an importable tool.

Important Classes

Environment

Environment loads and parses the given files. It can be initialized via:

• a file path - apk files can be loaded as well
• a folder path - loads all files in that folder (bad idea for folders with a lot of files)
• a stream - e.g., io.BytesIO, file stream,...
• a bytes object - will be loaded into a stream

ArisuFxPy can detect if the file is a WebFile, BundleFile, Asset, or APK.

The unpacked assets will be loaded into .files, a dict consisting of asset-name : asset.

All objects of the loaded assets can be easily accessed via .objects, which itself is a simple recursive iterator.

import io
import ArisuFxPy

# all of the following would work
src = "file_path"
src = b"bytes"
src = io.BytesIO(b"Streamable")

env = ArisuFxPy.load(src)

for obj in env.objects:
    ...

# saving an edited file
    # apply modifications to the objects
    # don't forget to use data.save()
    ...
with open(dst, "wb") as f:
    f.write(env.file.save())

Asset

Assets (SerializedFile class) are a container that contains multiple objects. One of these objects can be an AssetBundle, which contains a file path for some of the objects in the same asset.

All objects can be found in the .objects dict - {ID : object}.

The objects with a file path can be found in the .container dict - {path : object}.

Object

Objects (ObjectReader class) contain the actual files, e.g., textures, text files, meshes, settings, ...

To acquire the actual data of an object it has to be parsed first. This happens via the parse functions mentioned below. This isn't done automatically to save time as only a small part of the objects are usually of interest. Serialized objects can be set with raw data using .set_raw_data(data) or modified with .save() function, if supported.

For object types with m_Name you can use .peek_name() to only read the name of the parsed object without parsing it completely, which is way faster.

There are two general parsing functions, .parse_as_object() and .parse_as_dict(). parse_as_dict parses the object data into a dict. parse_as_object parses the object data into a class. If the class is a Unity class, it's stub class from ArisuFxPy.classes(.generated) will be used, if it's an unknown one, then it will be parsed into an UnknownObject, which simply acts as interface for the otherwise parsed dict. Some special classes, namely those below, have additional handlers added to their class for easier interaction with them.

The .patch(item) function can be used on all object (readers) to replace their data with the changed item, which has to be either a dict or of the class the object represents.

Example

for obj in env.objects:
    if obj.type.name == "the type you want":
        if obj.peek_name() != "the specific object you want":
            continue
        # parsing
        instance = obj.parse_as_object()
        dic = obj.parse_as_dict()

        # modifying
        instance.m_Name = "new name"
        dic["m_Name"] = "new name"

        # saving
        obj.patch(instance)
        obj.patch(dic)

Legacy

Following functions are legacy functions that will be removed in the future when major version 2 hits. The modern versions are equivalent to them and have a more correct type hints.

Legacy	Modern
read	parse_as_object
read_typetree	parse_as_dict
save_typetree	patch

Important Object Types

Now ArisuFxPy uses auto generated classes with some useful extension methods and properties defined in legacy_patch. You can search for a specific classes in the module ArisuFxPy.classes with your IDE's autocompletion.

Texture2D

• .m_Name
• .image converts the texture into a PIL.Image
• .m_Width - texture width (int)
• .m_Height - texture height (int)

Export

from PIL import Image
for obj in env.objects:
    if obj.type.name == "Texture2D":
        # export texture
        tex = obj.parse_as_object()
        path = os.path.join(export_dir, f"{tex.m_Name}.png")
        tex.image.save(path)
        # edit texture
        fp = os.path.join(replace_dir, f"{tex.m_Name}.png")
        pil_img = Image.open(fp)
        tex.image = pil_img
        tex.save()

Sprite

Sprites are part of a texture and can have a separate alpha-image as well. Unlike most other extractors (including AssetStudio), ArisuFxPy merges those two images by itself.

• .m_Name
• .image - converts the merged texture part into a PIL.Image
• .m_Width - sprite width (int)
• .m_Height - sprite height (int)

Export

for obj in env.objects:
    if obj.type.name == "Sprite":
        sprite = obj.parse_as_object()
        path = os.path.join(export_dir, f"{sprite.m_Name}.png")
        sprite.image.save(path)

TextAsset

TextAssets are usually normal text files.

• .m_Name
• .m_Script - str

Some games save binary data as TextAssets. As m_Script gets handled as str by default, use m_Script.encode("utf-8", "surrogateescape") to retrieve the original binary data.

Export

for obj in env.objects:
    if obj.type.name == "TextAsset":
        # export asset
        txt = obj.parse_as_object()
        path = os.path.join(export_dir, f"{txt.m_Name}.txt")
        with open(path, "wb") as f:
            f.write(txt.m_Script.encode("utf-8", "surrogateescape"))
        # edit asset
        fp = os.path.join(replace_dir, f"{txt.m_Name}.txt")
        with open(fp, "rb") as f:
            txt.m_Script = f.read().decode("utf-8", "surrogateescape")
        txt.save()

MonoBehaviour

MonoBehaviour assets are usually used to save the class instances with their values. The structure/typetree for these classes might not be contained in the asset files. In such cases see the 2nd example (TypeTreeGenerator) below.

• .m_Name
• .m_Script
• custom data

Export

import json

for obj in env.objects:
    if obj.type.name == "MonoBehaviour":
        # export
        # save decoded data
        tree = obj.parse_as_dict()
        fp = os.path.join(extract_dir, f"{tree['m_Name']}.json")
        with open(fp, "wt", encoding = "utf8") as f:
            json.dump(tree, f, ensure_ascii = False, indent = 4)

        # edit
        tree = obj.parse_as_dict()
        # apply modifications to the data within the tree
        obj.patch(tree)

TypeTreeGenerator

ArisuFxPy can generate the typetrees of MonoBehaviours from the game assemblies using an optional package, TypeTreeGeneratorAPI, which has to be installed via pip. ArisuFxPy will automatically try to generate the typetree of MonoBehaviours if the typetree is missing in the assets and env.typetree_generator is set.

import ArisuFxPy
from ArisuFxPy.helpers.TypeTreeGenerator import TypeTreeGenerator

# create generator
GAME_ROOT_DIR: str
# e.g. r"D:\Program Files (x86)\Steam\steamapps\common\Aethermancer Demo"
GAME_UNITY_VERSION: str
# you can get the version via an object
# e.g. objects[0].assets_file.unity_version

generator = TypeTreeGenerator(GAME_UNITY_VERSION)
generator.load_local_game(GAME_ROOT_DIR)
# generator.load_local_game(root_dir: str) - for a Windows game
# generator.load_dll_folder(dll_dir: str) - for mono / non-il2cpp or generated dummies
# generator.load_dll(dll: bytes)
# generator.load_il2cpp(il2cpp: bytes, metadata: bytes)

env = ArisuFxPy.load(fp)
# assign generator to env
env.typetree_generator = generator
for obj in objects:
    if obj.type.name == "MonoBehaviour":
        # automatically tries to use the generator in the background if necessary
        x = obj.parse_as_object()

AudioClip

• .samples - {sample-name : sample-data}

The samples are converted into the .wav format. The sample data is a .wav file in bytes.

clip: AudioClip
for name, data in clip.samples.items():
    with open(name, "wb") as f:
        f.write(data)

Font

Export

if obj.type.name == "Font":
    font: Font = obj.parse_as_object()
    if font.m_FontData:
        extension = ".ttf"
        if font.m_FontData[0:4] == b"OTTO":
            extension = ".otf"

    with open(os.path.join(path, font.m_Name+extension), "wb") as f:
        f.write(font.m_FontData)

Mesh

• .export() - mesh exported as .obj (str)

The mesh will be converted to the Wavefront .obj file format.

mesh: Mesh
with open(f"{mesh.m_Name}.obj", "wt", newline = "") as f:
    # newline = "" is important
    f.write(mesh.export())

Renderer, MeshRenderer, SkinnedMeshRenderer

ALPHA-VERSION

• .export(export_dir) - exports the associated mesh, materials, and textures into the given directory

The mesh and materials will be in the Wavefront formats.

mesh_renderer: Renderer
export_dir: str

if mesh_renderer.m_GameObject:
    # get the name of the model
    game_obj_reader = mesh_renderer.m_GameObject.deref()
    game_obj_name = game_obj_reader.peek_name()
    export_dir = os.path.join(export_dir, game_obj_name)
mesh_renderer.export(export_dir)

Texture2DArray

WARNING - not well tested

• .m_Name
• .image converts the texture2darray into a PIL.Image
• .m_Width - texture width (int)
• .m_Height - texture height (int)

Export

import os
from PIL import Image
for obj in env.objects:
    if obj.type.name == "Texture2DArray":
        # export texture
        tex_arr = obj.parse_as_object()
        for i, image in enumerate(tex_arr.images):
            image.save(os.path.join(path, f"{tex_arr.m_Name}_{i}.png"))
        # editing isn't supported yet!

Configurations

There're several configurations and interfaces that provide the customizability to ArisuFxPy.

Unity CN Decryption

The Chinese version of Unity has its own builtin option to encrypt AssetBundles/BundleFiles. As it's a feature of Unity itself, and not a game specific protection, it is included in ArisuFxPy as well. To enable encryption simply use the code as follow, with key being the value that the game that loads the bundles passes to AssetBundle.SetAssetBundleDecryptKey.

import ArisuFxPy
ArisuFxPy.set_assetbundle_decrypt_key(key)

Unity Fallback Version

In case ArisuFxPy failed to detect the Unity version of the game assets, you can set a fallback version. e.g.

import ArisuFxPy.config
ArisuFxPy.config.FALLBACK_UNITY_VERSION = "2.5.0f5"

Disable Typetree C-Implementation

The C-implementation of typetree reader can boost the parsing of typetree by a lot. If you want to disable it and use pure Python reader, you can put the following 2 lines in your main file.

from ArisuFxPy.helpers import TypeTreeHelper
TypeTreeHelper.read_typetree_boost = False

Custom Block (De)compression

Some game assets have non-standard compression/decompression algorithm applied on the block data. If you wants to customize the compression/decompression function, you can modify the corresponding function mapping. e.g.

from ArisuFxPy.enums.BundleFile import CompressionFlags
flag = CompressionFlags.LZHAM

from ArisuFxPy.helpers import CompressionHelper
CompressionHelper.COMPRESSION_MAP[flag] = custom_compress
CompressionHelper.DECOMPRESSION_MAP[flag] = custom_decompress

• custom_compress(data: bytes) -> bytes (where bytes can also be bytearray or memoryview)
• custom_decompress(data: bytes, uncompressed_size: int) -> bytes

Custom Filesystem

ArisuFxPy uses fsspec under the hood to manage all filesystem interactions. This allows using various different types of filesystems without having to change ArisuFxPy's code. It also means that you can use your own custom filesystem to e.g. handle indirection via catalog files, load assets on demand from a server, or decrypt files.

Following methods of the filesystem have to be implemented for using it in ArisuFxPy.

• sep (not a function, just the separator as character)
• isfile(self, path: str) -> bool
• isdir(self, path: str) -> bool
• exists(self, path: str, **kwargs) -> bool
• walk(self, path: str, **kwargs) -> Iterable[List[str], List[str], List[str]]
• open(self, path: str, mode: str = "rb", **kwargs) -> file ("rb" mode required, "wt" required for ModelExporter)
• makedirs(self, path: str, exist_ok: bool = False) -> bool

Credits

• Original Author & Upstream: K0lb3 - UnityPy
• Forked, Enhanced & Maintained by: ArisuGpt - ArisuFxPy

First of all, thanks a lot to all contributors of UnityPy and ArisuFxPy, and all of its users.

Also, many thanks to:

• Perfare for creating and maintaining and every contributor of AssetStudio
• ds5678 for the TypeTreeDumps and the custom minimal Tpk format
• Razmoth for figuring out and sharing Unity CN's AssetBundle decryption (src).
• nesrak1 for figuring out the Switch texture swizzling
• xiop_13690 (discord) for figuring out unsolved issues of the ManagedReferencesRegistry

⚖️ Legal Disclaimer & Fair Use Notice