For furigana, can katakana be used instead of hiragana?


From the first day I started to learn Japanese, I saw people use _hiragana_ to
help read _kanji_ , they are usually written on the top of those _kanji_ s.

But recently I also saw some Japanese use _katakana_ , to not only spell and
mimic the sound of the foreign words, but also write them on the top of
_kanji_ to aid in their reading, instead of _hiragana_.

Is this also okay or common practice? Are there any differences, or does it
not matter?




What you're talking about is called furigana (振り仮名). It's normally written in
hiragana script, except maybe in dictionaries sometimes when katakana is used
to indicate the Chinese reading. Another case for using katakana as furigana
is when you want to write a foreign pronunciation for a word written in kanji.
The [Wikipedia page](http://en.wikipedia.org/wiki/Furigana) for furigana gives
the example of 一角獣 (one horn beast) with furigana "ユニコーン" (unicorn). But those
are exceptions, in most cases, for difficult kanji, hiragana is used.

