Mac File Encoding

Each file on a Macintosh OS has two components, a "data fork", containing application specific data, and a separately stored user inaccessible "resource fork" containing creation information, file comments, and most importantly the application association information. Although this structure is efficient and effective, it is not compatible with the Internet. Since both components are required for operation, both components must be included when transferring files across the Internet. Therefore, numerous methodologies of creating a "unified" file have arisen into existence. In all cases, files must first be encoded. Encoding a file creates this "unified" file consisting of the "resource fork" appended to the "data fork". Once encoded the file is suitable for transmission over the Internet. Please note: Compressed files must also be encoded prior to transferring across the Internet.

The following methodologies are used for encoding: MacBinary, BinHex, UUencoding, and Base64. When transferring files via email attachments from a Mac to a Mac, BinHex is the clear choice. BinHex (.hqx), which stands for binary hexadecimal, converts the Macs 8-bit "resource fork" "data forks" into one 7-bit file. If transferring via browser or FTP client, you also can use MacBinary (.bin), which creates a smaller file than BinHexing. MacBinary, however, is not for email attachments because it creates an 8-bit file, which, unlike a 7-bit file, has problems in the email gateways and can become corrupted.

When sending files from Mac to Windows there are two common choices. Base64 seems to be on its way to becoming the standard. Its useful for all Internet transfer and seems to create the smallest file. The other option is UUencoding (.UU). As with other encoding, both convert 8-bit files to 7-bit. However, neither is great when it comes to the Macs two forks. Base64 may be your best choice, but its rather new and not all programs may implement it the same. UUencoding definitely works with only the Macs data fork, losing any information that may be stored in the resource fork. This is not always a problem since not all files use the resource fork for critical information. For example, you’re OK with MS Word 97/98 or JPG files as well as with text files that don’t contain formatting. Applications aren’t candidates for this, but you wouldn’t send Mac programs to non-Mac users anyway. The best advice is to send a file as a test to see if it will arrive intact.

Other encoding methods can convert both forks of a Mac file into one 8-bit file, then uses Base64 encoding to convert that file to a 7-bit file. This is recommended as the best format if you’re sending files to a user whose mail client supports multipurpose Internet mail extensions (MIME), as most do. MIME actually is not encoding but a mapping scheme that lets you assign file types to appropriate applications for processing.

Netscape and other web Browsers have no built in file decompression or decoding capabilities and rely on 'helper applications', such as MIME, to handle ALL file decoding and decompression. The best Mac utility is Stuff-It Expander for decoding and decompressing such files. This must be setup in your browser in order to do this upon downloading.