I always knew that Mac operating systems had a concept of "resource forks" but have just learned that this feature has in fact been deprecated since the arrival of OS X.

I also just discovered the mdls terminal command that lists metadata.

Does some or any of this metadata come from resource forks? If not, where is the metadata stored? Or is the metadata generated each time it's needed?


The meta data is stored in so called extended file attributes. The extended file attributes are stored in a named fork.

So in essence forks are still very much used on OS X. However, the specific "resource fork" as managed by the Resource Manager API is deprecated, as you describe.

  • Extended attributes are not a named fork. They're a separate feature of the file system. In fact, under APFS, the resource fork is stored as an extended attribute named com.apple.ResourceFork! – user101978 Feb 7 '18 at 21:47
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    @duskwuff The answer was written before APFS was a thing. On HFS+ extended attributes are in fact stored in a named fork. However, resource forks and named forks are not the same thing. – jksoegaard Feb 8 '18 at 8:55
  • @jksoegaard: What was the name of that named fork? Or if it is not a single unchanging name like the resource fork, how was the name derived? – hippietrail Mar 8 at 2:26

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