28

.28MacBinary II Archive

Apple Computer · 1985

Developer
Apple Computer
Category
Archives
MIME Type
application/x-macbinary
First Released
1985
Open Format
Yes
File Signature
0402 (Hex)
At a Glance
.28
MacBinary II Archive

A format for bundling Mac files and their metadata for easier transfer.

Reviewed on May 7, 2026
Compression
Binary
Transparency
No
Editability
Low
Best for
Mac file bundling

Key Features

  • Combines data and resource forks into a single file.
  • Preserves Mac-specific file attributes and metadata.
  • Facilitates file transfer between Mac and non-Mac systems.
  • Originally designed for classic Mac OS.

Best For

  • Preserving Mac-specific file attributes.
  • Ensuring compatibility when transferring files from old Macs.
  • Bundling single files with their extended Mac metadata.

Less Ideal For

  • Compressing multiple files or large directories.
  • Modern file sharing or cloud storage.
  • Cross-platform compatibility with modern operating systems.
  • Archiving for long-term preservation without specialized tools.

Common Use Cases

  • Transferring Macintosh files via email or FTP.
  • Archiving older Macintosh software or documents.
  • Sharing files between classic Mac OS and other operating systems.
  • Bundling applications with their associated resources.

How to Open It

  1. On modern macOS, use tools like The Unarchiver or older Mac emulation software.
  2. On Windows, specialized decompression utilities like StuffIt Expander (older versions) or dedicated MacBinary extractors can often open them.
  3. Some file archiving suites might offer support for .28 files.

What is a .28 file?

MacBinary II is a file format primarily used on classic Mac OS to bundle a Mac file's data fork and resource fork into a single file. This was crucial for transferring Mac files to other systems, especially non-Mac platforms, as it preserved essential metadata and resource information. It essentially acts as a container, wrapping the original file while adding specific Mac OS attributes. While largely superseded by modern archive formats and cloud sharing, it remains relevant for users working with older Mac software or archives.

Programs That Open .28 Files

PlatformProgram
WindowsStuffIt Expander (older versions)Free
macOSThe UnarchiverFree
macOS Archive Utility (limited support)FreeOfficial
LinuxunarFree

How to Convert .28 Files

FormatMethod
.BINEmulation software, Dedicated extractors

Common Problems with .28 Files

⚠️ Modern operating systems may not recognize the format directly.
Use dedicated archiving tools like The Unarchiver or StuffIt Expander to extract the contents.
⚠️ Metadata might be lost or misinterpreted on non-Mac systems.
Ensure you are using software designed to interpret MacBinary correctly, or convert to a more universal format if possible.

Frequently Asked Questions

What is a .28 file?

.28 files are MacBinary II archives, used on classic Mac OS to bundle a file's data and resource forks, along with its metadata, for easier transfer.

Can I open .28 files on Windows?

Yes, you can often open .28 files on Windows using specialized archive utilities like older versions of StuffIt Expander or other Mac file extractors.

Is .28 a compression format?

While it bundles files, .28 itself is not primarily a compression format but a container designed to preserve Mac-specific file attributes during transfer.

Technical Details

MacBinary II files are binary files that contain the original file's data and resource forks. They also include metadata such as file type, creator codes, and Finder flags. The format specifies a header followed by the resource fork data and then the data fork data.

Did You Know?

The .28 extension was originally used for specific types of MacBinary files, later standardized into the general 'application/x-macbinary' MIME type.
MacBinary was essential for making Macintosh files usable on systems like MS-DOS or Unix before modern cross-platform file systems and archive formats became widespread.

Security Information

As with any archive file, exercise caution when opening .28 files from untrusted sources, as they could potentially contain malicious code if the original bundled file was compromised.

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