BUNDLE File

What are BUNDLE files and how to open them

Are you having problems opening a BUNDLE file or are you simply curious about its contents? We're here to explain the properties of these files and provide you with software that can open or handle your BUNDLE files.

What is a BUNDLE file?

BUNDLE files have multiple uses, and Krita Resource Bundle is one of them. Read more about the other uses further down the page.

Krita Resource Bundle

Krita Resource Bundle files are used by Krita to package together multiple digital painting resources - brush presets, patterns, gradients, workspaces, color palettes, SVG symbols, layer styles, and similar - into a single compressed archive. They allow users to share, import, export or disable sets of resources in one step rather than handling each individually.

These bundles are created within Krita via its Resource Manager or Create Bundle wizard, where a user selects which resources to include, picks metadata like author, title and icon, and then saves the bundle for distribution. To use a bundle, Krita imports it into the resource library (via Manage Resource Libraries), and it then appears alongside other resource folders; it can be activated or deactivated depending on whether its resources should be available for use.

Under the hood the bundle format is a ZIP-style archive that contains resource files, a manifest, metadata including author and license, and structured information about tags, creators, and included resources. The bundle includes entries such as MIMETYPE and APPLICATION and can be recognized by the signature bytes PK at the start, plus strings like X-KRITA-RESOURCEBUNDLE in its content.

How to open BUNDLE files

Important: Different programs may use files with the BUNDLE file extension for different purposes, so unless you are sure which format your BUNDLE file is, you may need to try a few different programs.

While we have not verified the apps ourselves yet, our users have suggested two different BUNDLE openers which you will find listed below.

Last updated: August 25, 2026

All known file formats using extension .BUNDLE

While Krita Resource Bundle is a popular type of BUNDLE-file, we know of 2 different uses of the .BUNDLE file extension. Different software may use files with the same extension for different types of data.

Unity UnityFS Asset Bundle

Unity UnityFS Asset Bundle files are archive containers produced by the Unity game engine for packaging non-code assets so they can be loaded at runtime. They are built when creating downloadable or platform-specific content (such as textures, prefabs, audio, and entire scenes) that isn't compiled into the executable. These bundles let developers deliver updates or optional content separately from the main game build.

Unity writes these files using its BuildPipeline API or through the Addressables system; Unity packages decide which assets to include and how to compress them based on target platforms. At runtime, Unity loads a bundle, mounts it as a virtual archive, locates the internal serialized object files, resolves dependencies across bundles via manifests or stored dependency fields, and extracts individual assets as requested. Scenes are handled specially via separate serialized files for scene hierarchy and for shared assets.

Compression in these bundles can be full-file (e.g. LZMA), chunk-based (e.g. LZ4), or uncompressed, depending on build options.

Internally each file starts with the ASCII signature UnityFS at offset zero. The header includes Unity-format version metadata, followed by one or more SerializedFile blocks.

Various apps that use files with this extension

These apps are known to open certain types of BUNDLE files. Remember, different programs may use BUNDLE files for different purposes, so you may need to try out a few of them to be able to open your specific file.

Help us help others

File.org helps thousands of users every day, and we would love to hear from you if you have additional information about BUNDLE file formats, example files, or compatible programs. Please use the links below or email us at submit@file.org to discuss further.