How to make hybrid CD-ROMs
What is a hybrid CD?
The term hybrid CD-ROM denotes a CD with both a Macintosh volume containing a Macintosh filesystem (HFS or HFS+, also known as extended HFS) and a PC-readable filesystem (either ISO9660 or MS-Joliet). On PCs, only the ISO9660/Joliet data will be visible, whereas a Mac can see both filesystems (albeit without the long filenames supported by the Joliet extensions) but will auto-open only the Mac volume.
When are hybrid CDs needed?
When a CD contains only data files that need to be accessible on multiple platforms, it is not necessary to create a hybrid CD. Instead, an ISO9660 cross-platform CD can be made, with all files visible on both PCs and Macs. If a Linux system is used for burning, even the Rockridge extensions supporting Unix file ownership and permissions can be applied, so a true multi-platform CD is possible. However, ISO9660 CDs only support short filenames following MS-DOS conventions: 8 characters for the filename and 3 for the file extension, everything in uppercase, and only alphanumeric characters and underscore are allowed (there are extensions allowing any MS-DOS 8.3 character filename, or even long filenames up to 30 characters, which will still work on most systems).
So when are true hybrid CDs necessary to avoid creating two separate CDs for PC and Mac? As only they provide a true Macintosh filesystem, only hybrid CDs will preserve file creator type information, and thus only they will allow the Macintosh user to open files by double-clicking. Macintosh volumes also allow fine control over the appearance of the volume when it is opened (icons, layout, visibility), allowing a professional-looking CD for distribution. Finally, only on a Mac volume can a file be made to auto-open upon CD-insertion. Note: in Roxio Toast, the true hybrid format is called custom hybrid and is hidden under Other. By default, Toast will create data-only "hybrid" CDs, which are single-volume CDs just like ISO9660 CDs, but with long filename support.
Naming: When you place hyperlinked documents (e.g. webpages or PDF files) on your cross-platform CDs, make sure that all the hyperlinks reference the documents by their short 8.3 DOS filename, which is the only name visible on the Macintosh. To avoid problems, it is recommended to use such short filenames from the beginning. Note that in some versions of Windows, renaming a document like "mylongfile.html" to a short name with the same prefix, here "mylongfi.htm" does not change the underlying DOS filename (usually "mylong~1.htm") — you need to actually change the first six letters to cause the DOS name to change.
Also make sure to only use relative links, not absolute file:///-type links, as always for CD or web distribution.
Sharing: All data files such as images, Quicktime movies, webpages, Flash animations, or Acrobat PDF documents can be shared between the Mac and ISO (PC) volume, so only executables and files with platform-specific information (e.g. a ReadMe file) need to be duplicated on the CD. This helps saving space. In particular, you should keep this in mind when designing your media, so you create cross-platform compatible movies and sounds, e.g. RealVideo, RealAudio, or flattened Quicktime movies.
How is it done?