Does metadata alter hash for a file?

Question

We know that hash value for a file is independent of filename. And I did some experiment and it proved that in terms of mac os, the change of label(red,..), keywords, description (in open meta) of a file do not alter hash value.

But the change of metadata in jpeg does change the hash.

So I start to wonder why it holds? Any clue or inspiring tutorial?

Answer 1

The tool that you used apparently hashed what the OS considers as file contents, which in the case of a JPEG includes some metadata defined in the JPEG standard. Keywords, description, etc. are stored outside of the file contents proper by the filesystem.

(What is considered data and what metadata can be rather arbitrary and dependent on the context, e.g. the processing application and platform.)