Someone sent me photos that are about 20 years old and they are from a Mac they say. PhotoShop, Paint, etc. can not figure out how to open them.

They do not appear to have a specified format from what I can tell, ie no extension. I tried properties and they just come up as "file". When I click to open I get unknown file type and when I try it in Paint for example I get either invalid bitmap file or unsupported format.

Is there anything I can do in a Windows environment to open them? I do not have access to a 20 year old Mac ... and I doubt one of the office stores would know anything about these files either.


  • If you cannot even tell us what image format they used, it will be difficult, to suggest any method to open them. "They were created on a Mac" isn't enough information to answer your question. – Ramhound Jan 30 '18 at 15:46
  • You say “20 year old MAC” and all that means is not much of anything. 20 years ago was 1998. It could be Photoshop or ClarisWorks or any number of things. – JakeGould Jan 30 '18 at 15:57
  • If you don't select the TrID option noted below, one could also rename the files to have arbitrary extensions and attempt to open them one at a time. That is to say, add a .jpg to see if it opens. If not, add a .bmp or a .tiff. Mac computers did not use extensions in the same manner as windows (back then) but this method is a work-around with some klutz factor. – fred_dot_u Jan 30 '18 at 16:40
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    A lot of file formats can be identified by the first few bytes of the file. Usually the first 4 bytes, but sometimes more. Can you open a few of these files in a hex editor and tell us what the first, let’s say 16, bytes of the files are? – Spiff Jan 30 '18 at 19:29

You could try identifing the format of the file 1st, you can know this by using this TrID

TrID can recognize over 9,000 file formats

find more info here

Once you identified the file format you can now look for the adecuate software to open them, if they are not supported by other software you could try this viewers to see if they work and maybe you can export them into another file format:

  • Filesee: It serves as a file viewer and as a disk explorer, since it includes a column to access the folders and subfolders of the disk. It supports more than 100 formats of text, image, video, sound, etc.
  • Free File Opener: Up to 200 formats is able to open this program and without the need to install other applications. In addition, with the guarantee of being a Microsoft partner.
  • Universal Viewer: One of the oldest file viewers, but no less practical. Open hundreds of formats, especially images. In addition, it is very practical to open unknown text files, as it attempts to decipher its contents

Hope it helps!!!

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    Be sure to download the definitions file along with the main program file. I overlooked that at first, but picked it up from the error message. TrID worked fine for some examples I chose. – fred_dot_u Jan 30 '18 at 16:38

Classic Mac OS (before Mac OS X) stored file type and creator codes in a special place in the filesystem that non-Mac filesystems don’t really have. This info is called the “Finder metadata”. Depending on how those files got to you, that info may or may not have been preserved.

Also note that some common Mac-specific graphics/image file formats for that era stored important information in the “Resource Fork”, which is another place the Mac HFS filesystem could store some of a file’s data, that non-Mac filesystems don’t really have. And again, depending on how these files got packaged up and transferred from the Mac to your Windows PC, that information may or may not have been preserved. This could be a problem if the image was some Mac-specific graphic’s app’s proprietary format, and that developer chose to store important info in the resource fork.

FYI, the part of a classic Mac file that’s the same cross-platform is called the “Data Fork”. So if you have, say, a text or GIF or JPEG file, if all you have is the data fork, you’re still okay. There are ways to discover the type and read the file like any other text or GIF or JPEG file.

If you lost the Finder metadata, no worries, there are other ways to find the file’s type. If you lost the resource forks, depending on how Mac-specific the file format was, you might be stuck. But if these were standard cross-platform file formats, you’re probably okay even without resource forks.

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  • Sorry but I am a novice ... I apparently have something because there are two folders one with the photos and the other called _MACOSX. That folder seems to have the same file names but they are ._and then the file name. Everything was zipped and emailed in a folder but since I don't under stand the Mac operating system I don't know what I am doing. – Allan Jan 30 '18 at 21:53
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    @Allan That’s good news. Those matching ._filename files are a common way that Apple stores the Finder metadata and resource forks of old Mac files, when they need to go to non-Mac filesystems. It’s a format called AppleDouble. If you post one of those ._filename files for one of your photo files, I can probably decode it and tell you the file type and maybe even the app that created it. – Spiff Jan 30 '18 at 23:25

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