A Deep Dive into Apple's .car File Format

Sun, 25 Jan 2026 19:31:52 +0100

Every modern iOS, macOS, watchOS, and tvOS application uses Asset Catalogs to manage images, colors, icons, and other resources. When you build an app with Xcode, your .xcassets folders are compiled into binary .car files that ship with your application. Despite being a fundamental part of every Apple app, there is little to none official documentation about this file format.

In this post, I’ll walk through the process of reverse engineering the .car file format, explain its internal structures, and show how to parse these files programmatically. This knowledge could be useful for security research and building developer tools that does not rely on Xcode or Apple’s proprietary tools.

As part of this research, I’ve built a custom parser and compiler for .car files that doesn’t depend on any of Apple’s private frameworks or proprietary tools. To make this research practical, I’ve compiled my parser to WebAssembly so it runs entirely in your browser, so no server uploads required. You can drop any .car file into the interactive demo below to explore its content. I’m considering open-sourcing these tools, but no promises yet!

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A Deep Dive into Apple's .car File Format