MacBinary is a

file format A file format is a Computer standard, standard way that information is encoded for storage in a computer file. It specifies how bits are used to encode information in a digital storage medium. File formats may be either proprietary format, pr ...

that combines the data fork and the

resource fork A resource fork is a fork of a file on Apple's classic Mac OS operating system that is used to store structured data. It is one of the two forks of a file, along with the data fork, which stores data that the operating system treats as unstruct ...

of a

classic Mac OS Mac OS (originally System Software; retronym: Classic Mac OS) is the series of operating systems developed for the Mac (computer), Macintosh family of personal computers by Apple Computer, Inc. from 1984 to 2001, starting with System 1 and end ...

file into a single file, along with HFS's extended

metadata Metadata (or metainformation) is "data that provides information about other data", but not the content of the data itself, such as the text of a message or the image itself. There are many distinct types of metadata, including: * Descriptive ...

. The resulting file is suitable for transmission over

FTP The File Transfer Protocol (FTP) is a standard communication protocol used for the transfer of computer files from a server to a client on a computer network. FTP is built on a client–server model architecture using separate control and dat ...

, the

World Wide Web The World Wide Web (WWW or simply the Web) is an information system that enables Content (media), content sharing over the Internet through user-friendly ways meant to appeal to users beyond Information technology, IT specialists and hobbyis ...

, and

electronic mail Electronic mail (usually shortened to email; alternatively hyphenated e-mail) is a method of transmitting and receiving Digital media, digital messages using electronics, electronic devices over a computer network. It was conceived in the ...

. The documents can also be stored on computers that run operating systems with no HFS support, such as

Unix Unix (, ; trademarked as UNIX) is a family of multitasking, multi-user computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, a ...

Windows Windows is a Product lining, product line of Proprietary software, proprietary graphical user interface, graphical operating systems developed and marketed by Microsoft. It is grouped into families and subfamilies that cater to particular sec ...

. MacBinary was widely supported on the

Macintosh Mac is a brand of personal computers designed and marketed by Apple Inc., Apple since 1984. The name is short for Macintosh (its official name until 1999), a reference to the McIntosh (apple), McIntosh apple. The current product lineup inclu ...

and was built into most communications programs on that platform. Similar solutions were built into most

data compression In information theory, data compression, source coding, or bit-rate reduction is the process of encoding information using fewer bits than the original representation. Any particular compression is either lossy or lossless. Lossless compressi ...

applications on the Mac, and although these did not require MacBinary to survive transmission across non-Mac systems, MacBinary was often added in these cases to preserve longer filenames and other features. The dual-fork nature of the HFS system was not used on

Mac OS X macOS, previously OS X and originally Mac OS X, is a Unix, Unix-based operating system developed and marketed by Apple Inc., Apple since 2001. It is the current operating system for Apple's Mac (computer), Mac computers. With ...

, and MacBinary has largely disappeared.

Description

In contrast to other computers of the era,

applications included both computer code as well as a large number of ''resources'' that were used by the

operating system An operating system (OS) is system software that manages computer hardware and software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ...

(OS) itself. These resources were also widely used in documents to store

rich media Interactive media refers to digital experiences that dynamically respond to user input, delivering content such as text, images, animations, video, audio, and even AI-driven interactions. Over the years, interactive media has expanded across ...

like sounds and images. However, the resource system had the significant limitation that the maximum size of any single resource was only 32 kB, far too small for storing document data. To address this, Apple introduced the concept of ''forks'', allowing any file in the filesystem to have both a resource fork and a data fork. Physically these were separate files, but the OS would ensure the two separate files were always treated as a single object, so dragging it to a

floppy disk A floppy disk or floppy diskette (casually referred to as a floppy, a diskette, or a disk) is a type of disk storage composed of a thin and flexible disk of a magnetic storage medium in a square or nearly square plastic enclosure lined with a ...

in the Finder would copy both forks. This presented a serious problem when the file had to be stored on other computer systems. Those systems, unaware of the fork concept, would have to store the two forks as separate files. This presented the possibility that the two would be separated at some point, or not properly recombined when they were transmitted back to the Mac. This problem led to a number of solutions that combined the two forks together into a single file, and then automatically pulling them back apart when they reached another Mac. MacBinary was one of the most popular solutions, although

BinHex BinHex, originally short for "binary-to-hexadecimal", is a binary-to-text encoding system which was used on the classic Mac OS for sending binary files over email. BinHexed files take up more space than the original files, but avoid data corruption ...

was also used on

UseNet Usenet (), a portmanteau of User's Network, is a worldwide distributed discussion system available on computers. It was developed from the general-purpose UUCP, Unix-to-Unix Copy (UUCP) dial-up network architecture. Tom Truscott and Jim Elli ...

, where data transfer was not

8-bit clean ''8-bit clean'' is an attribute of computer systems, communication channels, and other devices and software, that process 8-bit character encodings without treating any byte as an in-band control code. History Until the early 1990s, many progr ...

. Apple's own solutions, AppleSingle and AppleDouble, were never widely adopted in the user community. Files encoded with MacBinary, regardless of the version, usually have a .bin or .macbin

file extension File or filing may refer to: Mechanical tools and processes * File (tool), a tool used to remove fine amounts of material from a workpiece. ** Filing (metalworking), a material removal process in manufacturing ** Nail file, a tool used to gen ...

appended to the ends of their filenames. E-mail programs such as Eudora can extract and decode MacBinary mail messages. Most dedicated FTP programs for the Mac, such as Fetch and Transmit, transparently decode MacBinary files they download. MacBinary is similar to

, but MacBinary produces

binary file A binary file is a computer file that is not a text file. The term "binary file" is often used as a term meaning "non-text file". Many binary file formats contain parts that can be interpreted as text; for example, some computer document files ...

s as opposed to

ASCII ASCII ( ), an acronym for American Standard Code for Information Interchange, is a character encoding standard for representing a particular set of 95 (English language focused) printable character, printable and 33 control character, control c ...

text. Thus, MacBinary files are smaller than BinHex files, but older applications and servers are more likely to corrupt them.

History

The first incarnation of MacBinary was released in 1985. The standard was originally specified by Dennis Brothers (author of the terminal program MacTEP and later an Apple employee), BinHex author Yves Lempereur,

PackIt PackIt is a software data compression utility for archiving and compressing files on the Apple Macintosh platform. It was the first such program to see widespread use on the Mac, and most Mac software archives accepted uploads only in PackIt forma ...

author Harry Chesley, et al. then added support for MacBinary into BinHex 5.0, using MacBinary to combine the forks instead of his own methods. Most

terminal program A terminal emulator, or terminal application, is a computer program that emulates a video terminal within some other display architecture. Though typically synonymous with a shell or text terminal, the term ''terminal'' covers all remote termi ...

s and

internet The Internet (or internet) is the Global network, global system of interconnected computer networks that uses the Internet protocol suite (TCP/IP) to communicate between networks and devices. It is a internetworking, network of networks ...

utilities added built-in MacBinary support during this period as well. Two years later it was updated to MacBinary II, to accommodate changes in Mac OS. MacBinary II remained compatible with subsequent updates of the operating system for some time. This changed with the release of

Mac OS 8 Mac OS 8 is the eighth major release of the classic Mac OS operating system for Macintosh computers, released by Apple Computer on July 26, 1997. It includes the largest overhaul of the classic Mac OS experience since the release of System 7 ...

, which necessitated the release of MacBinary III in 1996. In the meantime, Apple itself had released the AppleSingle and AppleDouble formats, which serve the same purpose as MacBinary, but correct some problems with it.

References

* Dennis Brothers
"Macintosh Binary Transfer Format 'MacBinary' Standard (Proposal)"
Micro-networked Apple User's Group (CompuServe), 1985 * Adam Engst
"Macintosh Internet File Format Primer"
''TidBits'', 31 August 1991
"comp.sys.mac.comm FAQ"

External links

Mac Binary Converter
an open source tool for converting between different Macintosh file encodings.
macutils
converts between different Macintosh file encodings
MacBinary II Spec

MacBinary II+ Spec
a proposed enhancement to MacBinary to incorporate a directory tree, never widely adopted. {{Compression Software Implementations Archive formats Computer-related introductions in 1985