What is the difference between the four kinds of Shift JIS?

The four kinds of Shift JIS are different from each other as described below:

(Shift JIS)The most basic Shift JIS, support for JIS level 1 and 2 Kanji characters.
(Mac OS)Based on Shift JIS, with extended support for such as Mac-dependent characters. Being used in OS 9 and earlier.
(Windows, DOS)Based on Shift JIS, with extended support for such as Windows-dependent characters.
(Shift JIS X0213)Support for JIS X 0213 character sets, which include JIS level 1 through 4 Kanji characters.

Though choosing an appropriate encoding varies from case to case, it is normally safer to use Japanese (Shift JIS). However, note that there are differences between these encodings in the way of dealing with particular characters as below:

Halfwidth Yen sign (¥)Halfwidth backslash (\)Halfwidth tilde (~)
(Shift JIS)AvailableReplaced with fullwidth backslashNot available
(Mac OS)AvailableAvailableAvailable
(Windows, DOS)Replaced with halfwidth backslashAvailableAvailable
(Shift JIS X0213)AvailableReplaced with fullwidth backslashReplaced with fullwidth tilde

See also