Determine the file type of a document

You may have saved a file with the wrong extension, for example a JPEG file with a .psd extension. You cannot open the file in Photoshop due to an error

If you cannot remember the actual file type the file should be you can use the following method to determine the true file type of a document


Selecting File > Get Info... from the macOS Finder will not accurately tell you the true file type of a document as it only looks a the file name to make the determination. The method outlined below using the Terminal reads into the file header to get the true file type.


  1. Open Terminal


  2. In Terminal type "file " (the word 'file' with a space after it)

    Type the word file with a space after it

  3. Drag the file you want to determine the file type of onto the Terminal window

    Drag file onto Terminal

  4. The path to the file and its name will appear in the Terminal window

    File path and name

  5. Hit the Return key to see the file type

    Look at the file data type


In this case, the file is named "mydocument.psd" but the file is actually a JPEG. Rename the file to "mydocument.jpg" to open in Photoshop.

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