Finder is odd

Discussion in 'macOS' started by RobHague, Sep 15, 2005.

  1. RobHague macrumors 6502

    Jul 8, 2005

    Why does it do that? I rename a file and they have .mp3 at the end but i can remove the .mp3 extenshion and it does not warn me - It appears to see it as an MP3 anyway regardless. Im confused. Are the other files named .mp3.mp3 :confused: :confused: What if i want to rename somethings extenshion.

    Also in finder ive set the option to display a thumbnail of a file. Ive noted that i have a lot of images ive saved from the web that do not show me thumbnails when inside finder - yet some do (ones ive saved in paint programs). What goes on?

  2. Jen5678 macrumors regular

    Nov 13, 2004
    if you right click on the file and go to get info is hide extension checked?
  3. RobHague thread starter macrumors 6502

    Jul 8, 2005

    hmmm, is there no way to set hide extenshion for every file on the system? I tried looking @ Finder > Preferences > Advanced and ticking the Show file extenshions and then unticking it but no joy.
  4. hayduke macrumors 65816


    Mar 8, 2005
    is a state of mind.
    2cents worth...

    I think that the Finder is smart enough to identify some file types with or without the proper tag. Certain filetypes can be "fingerprinted" without ambiguity.
  5. After G macrumors 68000

    After G

    Aug 27, 2003
    I think this is a hold-over from earlier Mac OSes that didn't need extensions to identify files. I like not having extensions determine what your file is, as you get yourself into situations like having viruses disguise themselves as songs on Windows.
  6. Nermal Moderator


    Staff Member

    Dec 7, 2002
    New Zealand
    OK, in the old OS, each file had two "tags" - filetype and creator. The filetype tag would indicate what type of file it was (such as MP3) and the creator tag would indicate which app it was created with (such as iTunes).

    Having two tags helps with compatibility - for example Word and TextEdit can both use the same file format, but each reads it slightly differently. By using the creator tag, each individual file can be opened using the "best" application.

    File extensions are really just for Windows compatibility. If a file does not have the filetype or creator tags, then the OS will use the file extension to "guess" the filetype (and will link it to the default app for that filetype).

    That doesn't really help, but at least it should help you understand what's going on :)

    Also, no accuracy guarantees :rolleyes:
  7. gekko513 macrumors 603


    Oct 16, 2003
    That's right. Finder can sometimes tell what kind of file it's looking at even if it doesn't have an extension.

    As for the image thumbnail. The thumbnail that you see when saving with Photoshop, isn't a thumbnail, it's a custom icon made by photoshop.

    If you want to view all images as thumbnails, go to View -> View Options and check Show Icon Preview (or something similar)
  8. Makosuke macrumors 603

    Aug 15, 2001
    The Cool Part of CA, USA
    Ok, the Finder behavior on this is very confusing, but as far as I can tell this is how it works:

    If the file does have a type and creator set, and the file extension matches what the Finder "expects" (for example, .mp3 and iTunes, .doc and Word) then it will let you delete it without complaint. This sort of makes sense, since the file is still properly identified.

    If the file does not have a type and creator that match the extension, or it has no type and creator at all (for example, a Word doc labeled .mp3 or an .avi downloaded from the internet), then deleting the extension will merely set the "Hide Extension" checkbox without actually deleting it. Furthermore, if you go back and type in a new extension at this point, the old one is still there, you just can't see it, so you end up with, for example, document.doc.mp3. Confusing.

    Lastly, if you try to change an existing and visible extension, whether it's "correct" or not, the Finder will ask you if you're sure.

    So, in this particular case, I assume the type and creator are set properly on those files, so deleting the .mp3 does nothing. Were they "unmarked" files, it would instead set the "Hide" flag.

    Background: The OSX Finder (don't think they've changed the priorities recently) checks the filetype and creator first, then falls back on the visible .something extension if there are none or it doesn't recognize them.

    This explains why you can have some .pdf files that open with Preview and others that open with Acrobat--either the types and creators reflect this, or the Acrobat ones are labeled while the ones that open in Preview have no type/cretator at all and the default app is Preview).

    The metadata system is really a better system for the most part, but the internet (not to mention Windows) and its lack of obvious metadata (though a similar system does actually exist on the web, MIME types) is the reason for Apple's push toward in-filename extensions. The fact that it's invisible and hard to change is also a bit annoying, and potentially confusing for novice users (the "open with" settings help, though).

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