What is the File Extension .rsrc?


Rsrc, or a file with the.rsrc extension, is a Macintosh resource file. Rsrc files are used by the Mac OS to store system-related data in a compressed format that requires less memory usage.


  • Created by programmer Bruce Horn, resource fork (.rsrc) files are a type of virtual memory originally created for use in the pre-Macintosh Apple Lisa in 1978.

Later Refinements

  • In 1985, Apple implemented resource fork files for the first time in a Macintosh model. The Macintosh XL used more advanced .rsrc files to reduce the memory consumption of the Mac XL down to 128 kilobytes.

How They Work

  • A file stores data in its data fork (such as .jpg) but stores other file information, such as its embedded icon graphic, in a resource fork. Most .rsrc files are automatically hidden from the user's view.

Opening .RSRC File

  • You can locate and open .rsrc files with Apple's ResEdit software in Mac OS 9 or earlier versions, but in OS X you need to use Apple's Terminal application to view or modify an .rsrc file by appending "/..namedfork/rsrc" to your command.

RSRC Files and Windows

  • Because .rsrc files are limited to a hard-drive format that Windows doesn't support, there currently is no way to open an .rsrc file in Windows.


  • Rsrc is a developer file that shouldn't be opened by most users. Changing the structure of the resource fork can cause file data loss and recovery problems.

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